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Title: Pottery, for Artists Craftsmen & Teachers
Author: Cox, George J.
Language: English
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Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

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Transcriber’s Note: The original publication has been replicated
faithfully except as shown in the TRANSCRIBER’S AMENDMENTS at the end of
the text. This etext presumes a mono-spaced font on the user’s device,
such as Courier New. Words in italics are indicated like _this_. Text
emphasized with bold characters or other treatment is shown like =this=.
Superscripts are indicated like this: S^{ta} Maria. Subscripts are
indicated like this: H_{2}O.

[Illustration]

[Illustration: “_He wrought a work upon the wheels, and the vessel that he
made of clay was marred in the hands of the Potter: so he made it again
another vessel, as seemed good to the Potter to make it._”--(JEREMIAH.)]



                                POTTERY,

                              FOR ARTISTS
                               CRAFTSMEN
                               & TEACHERS
                                   BY
                          GEORGE J COX, ARCA.
                  INSTRUCTOR in POTTERY & MODELLING AT
                 TEACHERS COLLEGE--COLUMBIA UNIVERSITY

                       ILLUSTRATED by the AUTHOR


                PRINTED IN THE UNITED STATES OF AMERICA

                            COPYRIGHT, 1914,
                        BY THE MACMILLAN COMPANY

           Set up and electrotyped. Published November, 1914.

                             Norwood Press
                 J. S. Cushing Co.--Berwick & Smith Co.
                        Norwood, Mass., U. S. A.


      “O Master, pardon me, if yet in vain
      Thou art my Master, and I fail to bring
      Before men’s eyes the image of the thing
      My heart is filled with.”

                                         --WILLIAM MORRIS.



                              EXPLANATION


In such a spacious craft as Pottery it is difficult to steer a fair course
between the empirical and the scientific. With that in mind this book sets
out to tell in simple terms some of the processes of Potting, practicable
to the student and to the more finished craftsman.

It is an intricate task to combine successfully the view-points of the
artist and the scientist; but it seems that, without neglecting the many
benefits bestowed by the advance of science, the Potter should stand with
artists rather than chemists. And what has been accomplished by loving,
patient craftsmanship may surely be done again only in such ways.

To the artist craftsman, for whom chiefly this book is intended, a little
scientific knowledge is a dangerous thing; for that reason no great stress
is laid on formulas and analysis. Unless thoroughly understood they are a
hindrance rather than an aid.

Although many schools teach elementary pottery, the expense of equipment
possibly delays its introduction on a larger scale. For that reason I have
preferred to err on the side of over-exactness of description and
profuseness of illustration.

The slight historical review and introductory remarks are to be excused on
the ground that they are intended to help to a study of the best work of
the best periods, and so to foster a taste for the finest Ceramics. This
is a vital matter when laying the foundations of a craft so fascinating
and so full of alluring avenues to beckon the student from the true path.

To the scientific critic I would offer a hundred books with a thousand
different compounds; amongst none of them will he find how to make a Sung
bowl or a Rakka drug pot.

This book will achieve its purpose if it sets one or two sincere students
to the making of some of the many beautiful objects of utility and art
with which the craft abounds. Then it will have done something, if never
so little, to accelerate the arrival of that time when the artist will
come once more into his own in the most ancient and noble of Crafts.

Some of the many books consulted, to which I am indebted, are given at the
end of the book. Among friends my thanks are especially due to Richard
Lunn, Esq., of the Royal College of Art, London, and to Professor Arthur
Wesley Dow of Teachers College, Columbia University, for my introduction
to and opportunity of further study of the Craft to which I subscribe
myself an humble devotee.

                                                  G. J. C.



                           TABLE OF CONTENTS


                                                         PAGE

         EXPLANATION                                      vii

         CHAPTER

            I.  HISTORICAL SUMMARY                          1

           II.  CLAYS AND PASTES                           19

          III.  BUILT SHAPES                               26

           IV.  MOULDING, CASTING, AND PRESSING            34

            V.  JIGGER AND JOLLEY WORK                     51

           VI.  THROWN SHAPES                              59

          VII.  TURNING OR SHAVING                         73

         VIII.  TILE-MAKING                                80

           IX.  DRYING: FINISHING                          89

            X.  FIRING BISCUIT                             93

           XI.  GLOST FIRING                              107

          XII.  GLAZES AND LUSTRES                        117

         XIII.  DECORATION                                129

          XIV.  FIGURINES                                 141

           XV.  KILNS                                     151

          XVI.  THE EDUCATIONAL VALUE OF POTTERY          170

         APPENDIX I.  EQUIPMENT FOR A SMALL POTTERY OR A
             SCHOOL                                       177

         APPENDIX II.  GLOSSARY AND GENERAL INFORMATION   185



              POTTERY FOR ARTISTS, CRAFTSMEN, AND TEACHERS



                               CHAPTER I

                           HISTORICAL SUMMARY

  “After this he led them into his garden, where was great variety
    of Flowers. Then said he again, Behold, the Flowers are diverse
    in stature, in quality, and colour, and smell, and virtue, and
    some are better than some.”

                                                 --BUNYAN.


Without attempting a history of pottery which, however brief, would be
somewhat out of place in a Craft Book, a short summary of its evolution,
emphasizing those periods in which it was most beautifully developed,
seems essential to help the beginner in the selection and appreciation of
good form, colour, and decoration. These are very vital matters and easily
overlooked in the struggle to acquire a craft that is full of fascination
from the first fumbled shape upon the wheel to the finished product of
time and art and craft.

Too much stress cannot be laid upon the importance of close study of the
best work, both ancient and modern; for it is a truism that however
handily a craftsman may work, his output will be worthless if he has not,
with his increasing powers of technique, developed a sound judgement and
refined taste. To-day, these alone can replace the lost traditions of the
old masters.

The Potter’s Craft had a coeval birth in various parts of the earth, but
the obscurity is such that no clear idea can be gained of its antiquity.
It was, probably, the first form of handicraft, if we except the
fashioning of flints and clubs. Accident or the funeral pyre may have
suggested the extraordinary durability the clay shape obtained when
burned, and doubtless siliceous glazes were first the result of chance.
All early work was built up by hand and for that reason possesses wide
mouths and simple forms. The introduction of the wheel is lost in a mist
of time, but drawings from the tombs of Beni Hassan show the potter at his
wheel substantially as he works in Asia to this day. The wheel-made or
thrown shape is distinguished by far more grace and symmetry than the
built shape, and by an infinitely greater variety of form.

In burial mounds from prehistoric Egypt are found many bowls and platters
rudely scratched, and the earliest examples from mounds, lake dwellings,
and tombs show the quick development of the pot, not only as an object of
utility, but as a vehicle of art. The first kinds of decoration were
incised lines followed by strappings and bandings, painted stripes and
scrolls and hieroglyphs, with later additions in slip and modelled clay.
Primitive wares from their method of production exhibit an interesting
similarity of shape and style in such widely divergent countries as China,
Egypt, and Peru.

It was only when the craftsman had acquired considerable dexterity that we
find his nationality influencing his shapes and producing the wonderful
variety in form and decoration that characterizes and distinguishes the
pottery of all nations. Once established, the prevalence of type is
strong. This traditional style is particularly noticeable in Egypt, much
modern work being identical with that of the early dynasties.

Before turning to more sophisticated work it would be well to learn the
lesson of simplicity and fitness here taught by primitive folks. The
simple beginning leads to the simple, strong, and satisfying end. Much of
this primitive work is inspiring for its freshness or naïveté; its
unspoiled innate taste allied to downright common sense. Properly
approached, it should be a sure corrective to any desire for unsightly
_new_ shapes or extravagance in decoration. A few careful studies will do
much to drive home this valuable lesson in fine, simple line and spacing.

In Egypt the thrown shape was not distinguished by any extraordinary
beauty or variety. Nevertheless their small _Ushabti_, glazed gods and
demons, show a very advanced knowledge of coloured enamels, and their
fabrication of a hard sandy paste for glazing shows the first great step
in the science of pottery. Their glaze was purely alkaline.

The Assyrians appear to have been the first to use coloured tin glazes,
and although few pieces of pottery survive, the enamelled friezes from
Korsobad and Sousa are striking evidence of their proficiency in
tile-making.

From Egypt and Mesopotamia the craft spread east and west to Phœnicia,
Attica, and Greece; through Persia and Arabia to India. Here it mingled
with currents from China, then invading Korea, Japan, and Siam, the united
floods rising until the potter was a power in every land.

Phœnician pottery forms, with Cretan and early Grecian, a beautiful
sequence from the primitive work of early dynasties to the refinements of
later Grecian wares.

It will prove an interesting and instructive study to trace the
developments that led finally to the zenith of Greek pottery. The
primitive Hissarlik ware leads through Mycenaean, Dipylon, Phalæron,
Rhodian, and Corinthian right up to the wonderful figure vases of about
300 B.C. Although limited in paste and colour, with a thin transparent
glaze or lustre, these vases were exquisitely fashioned. Large and small
shapes of wide diversity were decorated in black, red, and white, ornament
and figures both drawn straight on to the body with a sureness of touch
and refinement of line that excite the envy of a master. Many of their
forms are strongly influenced by contemporary bronze work and for that
reason are not the best guides for shapes. Their incomparable terra-cottas
known as Tanagras form a link between Pottery and Sculpture.

Again, from Phœnician work one may see dimly by way of Samian, Rhodian and
old Cairene wares the lineage of the royal wares of Persia, and recent
investigations point to Old Cairo as the birthplace of lustre.

From Persia come some of the finest pottery, painted in colours and
lustres, that the world can show. Their wares stand pre-eminent in that
class wherein the chief beauty is the painted decoration. Their one-colour
pieces, whilst not comparable with the Chinese, nevertheless reach a high
standard. Their lustres have never been surpassed or rarely equalled.
Their shapes are true potter’s shapes, and a delight to the eye. The
finest pieces were painted in simple blues, greens, reds, and faint
purples, with black pencilling. This appears to have been done on an
engobe of finely ground flint, and covered with an alkaline glaze giving a
broken white ground. This would account in some measure for the
extraordinary freshness of both drawing and colour. Later on raised
ornament, finely conceived and used with restraint, is seen along with
pierced decoration having translucent effects.

Rhodes and Damascus produced a somewhat coarser ware, but bold and free in
brushwork and varied with a bright red. Syrian pottery abounds in virile
individual shapes. Turkey also was not without a fine and vigorous style.

Much time can be most profitably spent studying the masterpieces of
Persia. A representative collection like that at South Kensington will
show vases, bottles, bowls, pots, and tiles in bewildering variety and of
infinite freshness. They are directly painted, with free renderings of
flowers within geometric forms and often with an inscription in rich
Arabic characters. The exquisite Moore Collection in the Metropolitan
Museum, New York City, is smaller but is remarkable for the unusually high
standard of taste shown in its acquisition. At its purest period human or
animal figures were rarely or never represented and those shapes or tiles
with such decoration belong to a more decadent but still fine period.

Again we have the eternal lesson of simplicity and fitness. Again it will
be borne in upon the student that originality does not mean weirdness, but
rather a fresh spontaneous treatment of simple, well-known natural forms,
with, above all, a fine appreciation of good line and space. No sincere
student can fail to develop here a respect and veneration of a craft and
of craftsmen capable of producing such glorious works.

From this teeming home the craft spread to Arabia and west across the
Mediterranean to Spain. Here in the twelfth century the Moors were
producing their famous Hispano-Mooresque lustred wares. Their large
plaques offer a wonderful variety of pure brushwork ornament with spirited
heraldic additions. Sometimes the backs of these dishes are as beautifully
lustred as the fronts.

For a proper appreciation of their purely geometric decoration and its
possibilities in pottery we must turn to the Alcazzar at Madrid. Here the
use of opaque tin glaze permitted the extensive use of a coarse body for
tiles and bricks. The Moors, however, first introduced glazes with a lead
base and from that time we begin to lose the fresh _wet_ colour always
associated with the alkaline glazes of the Persians. Analysis shows that
they used lead, but only occasionally and in small quantities, to aid
their lustres. The lustred wares of Spain declined late in the thirteenth
century, but not before its exportation to Italy by way of Majorca had
stimulated the production of Italian Majolica. Della Robbia, about 1415,
succeeded in colouring his tin glazes, and his finely modelled but
somewhat crudely coloured reliefs usher in the era of Italian Faience.
Patronized by the nobles the craft quickly took root and was blossoming
profusely at Urbino, Gubbio, Pesaro, Faenza and other cities at the end of
the fifteenth century.

Here we break ground and leave the chaste simplicity of the golden age to
riot a blaze of exuberant decoration. Scraffito, slip, inlaid, applied,
incised, raised, embossed and modelled and painted embellishments; all are
here. This era is chiefly notable for its splendid ruby lustres and the
remarkable power and freedom, amounting to absolute abandon, of the
brushwork and drawing shown by its artists. They used their lustres to
heighten the effects of their painting and the results are in keeping with
that romantic age. Alongside of it our best modern work is apt to look
spiritless and dull.

Much splendid work was produced in Italy at this period, but in such a
wide field there are naturally some places that exhibit technique rather
than art. The student must go into it with appreciative faculties alert
lest mere splendour should sweep him off his feet.

The wares and the potters of Italy penetrated north into Europe, to
France, the Holy Roman Empire and Britain, starting or stimulating what
was to prove an overwhelming flood of production. In Europe in pre-Roman
times, a coarse, unglazed, built-up ware was general, it being of simple,
somewhat clumsy but vigorous form, low-fired and friable. It was used
chiefly for cinerary purposes, the Germanic peoples having a decided
preference for vessels of horn, wood, or metal.

The Romans introduced the wheel and produced a far higher class of ware.
Their importation of the fine red Samian pottery resulted in the
fabrication of the vigorous Gallo-Roman and Romano-British pottery. This
was good in shape and paste and characteristically decorated with slip,
bosses, dots, and indentations. The later Gaulish work shows applied
figures and highly finished scroll work. After the decline of Rome, Saxon
and Germanic work shows a distinctly retrograde tendency. It is often
built up, strapped, banded, and bossed in imitation of the Romano-British.
Though coarse and lacking in finish, it is full of freshness and
character.

In Mediæval England, when pottery making was at a low ebb, the monasteries
and travelling guilds of potters produced splendid encaustic tiles. These
were inlaid with simple yet striking geometric designs, or animal or bird
forms, both heraldic and symbolic.

In Europe for many years the domestic pottery remained coarse and
primitive, showing still the arresting hand of the barbarian conquerors of
Rome. The first signs of the Italian Renaissance are to be found in the
rare Henri Deux or Orion ware. Palissy’s desperate and romantic search for
enamels was the prelude to the development of Rouen, Nevers, Lille,
Moustiers, Sèvres, Marseilles, and other less important potteries. In
France also early experiments led eventually to the fabrication of
porcelain much on the lines of English porcelain, a frit being used
instead of kaolin.

In Germany, as early as the fifteenth century, they produced fine
stoneware highly decorated with relief patterns and colours. After long
research Boettiger, by a lucky accident, discovered kaolin. Porcelain was
made at Dresden in 1709, and many of the Dresden figures show a remarkably
sympathetic alliance of potting, modelling and painting.

The success of the German ceramists led to a wide patronage of potters by
kings and princes which quickly spread the knowledge of porcelain
throughout Europe.

Long before this in the early part of the seventeenth century, potteries
were established at Delft in Holland. Here was made the well-known ware
painted in blue camaien on a fine white ground. This was for a time
produced in great quantities, and the process of painting directly on to
an absorbent ground led to a surprisingly fresh and skilful style.

In the middle of the seventeenth century English wares commenced to rise
from the stagnation in which they seemed sunk since Saxon times. Toft,
with his tygs and platters, Dwight, and his bellarmines, and Elers, with
turned shapes, started a movement which was eventually to send English
wares into all parts of Europe, even into the far Russias, to be known
everywhere for its excellent workmanship. And in this flood of production
in the seventeenth and eighteenth centuries was much that was technically
unrivalled despite the fact that the Art of the potter is sometimes far to
seek. Dwight is said to have produced a fritted porcelain in 1671, before
the discovery of kaolin. This is doubtful, but his persistent research
eventually led up to the fine pastes of Chelsea and Bow and the unrivalled
“fine earthenwares” of Staffordshire.

This European revival gained tremendous impetus from the importation by
the Portuguese of the wares of CHINA. The wide scope of its decoration,
both painted and modelled, pointed the way to most potters of the West
during the heyday of European pottery. The magnificent single-colour
pieces were not introduced until later when the break-up of the Empire
rendered them accessible to Europeans. It is to them that the student
must turn to see the summit of the potter’s art, which, it is logically
contended, commences on the wheel and ends at the glost oven with the
potter, the only attendant from the pot’s inception to its finish.
Painting or modelling is not essential to its perfection and unless
applied by a true disciple detracts rather than adds to the beauty of the
piece.

In China, where tradition holds that earthenware was first made in 2698
B.C., the art of the potter, in body, shape, glaze, and colour, through
centuries reached perfection. Porcelain is said to have been first made
about 200 B.C., but this date is conjectural. What we do know
unmistakably, however, is that the best work of their best periods is
unrivalled. Depending primarily on form and colour, with here and there a
subtle decoration in raised or incised line, in crackle or simple
brushwork, it stands alone, and despite the omnipotent chemistry of
to-day, defies imitation. Their forms are strong, bold, and dignified, yet
subtle and delicate, too. Then, added to a wonderful range of colours, was
a perfection of body that was for so long the despair of western
imitators. It is here at the altar of perfection amidst the chaste
richness of Tang and Sung and Ming that the true disciple must worship.
And to those who must eat bread as well as make pots it is to be pointed
out that these pieces at the time of their production fetched prices that
compare favourably with the “fancy” prices given to-day.

To the Japanese also in great measure the same tribute is due. Although
beginning later as disciples and scarcely getting so far as their masters,
their more limited range of colour and form is set off by their restrained
and even more tasteful decoration. The unique collection in the Boston
Museum is an amplification of this bald statement. They were often more
concerned with the touch and texture of the pot than the more obvious
appeal of decoration. Esoteric as it is to most occidentals it is rich in
a pure æstheticism and a deep and beautiful symbolism that is slowly but
surely having an influence on western art, just when it seems in some
danger of dying out in Japan. The hermit kingdom of Korea, despite its
midway position, produced pottery that is strangely beautiful and
distinctive and worth much more than a passing notice.

In China the art decadence of the eighteenth and nineteenth centuries,
coupled with internal revolutions, has sadly dimmed her plots, dispersed
her potters, and all but destroyed her priceless traditions.

For the further development of pottery in Europe and America and Asia the
student has many excellent books to consult. From the seventeenth century
the ramifications are rapid and all-embracing, giving, however, more joy
to the collector than to the artist. Modern work has made an enormous
advance in the science of the craft. Since the “Eighties” it shows signs
of a renaissance in æsthetics. Lustres of all shades, crystalline, star,
and crackle glazes with safe methods of oxidizing and reducing in the
fire, have been brought to perfection. Yet, with some few exceptions,
commerce seems writ large upon them all and their very perfection of
finish damns them in the eyes of an artist. Whichever way he looks, he
must return again and again to refresh his eyes with the inspiring
examples of the best that has survived from the near and far EAST.

Only an antiquarian humbug would wish to go back to ancient conditions
even to produce old pots. But it is only by seeing in so far as we may in
museums and books the works of these ancient yet ever modern potters; by
tracing their development, appreciating their qualities and attempting to
work as they worked, honestly and unaffectedly, that we shall begin to
approach the excellence and originality of their art. This study should
not of course obey the direction it all too frequently follows. The
slavish measuring by module and fraction of classic styles, the stark
geometric analysis of Moorish ornament or the laborious copying of Chinese
pattern is at best only art in cold storage. It should be self-evident
that where an alien style is consciously imitated the result is sterility
for the imitator. In others, it is apt to produce a powerful reaction
that results in _Futurism_ or some such self-conscious affectation. “The
Greeks did not draw from casts nor did the Persians haunt museums,” says
the harried student. No. But better than that, they were surrounded, if
not by beauty, at least by nature naked and unashamed. They lived not
easily maybe, but surely more gracefully, untrammelled by fashion, cult,
or craze.

      “The earth his sober Inn
      And quiet pilgrimage.”

Their best work seems ever fresh, spontaneous, and untired. It must have
been done with a spirit and real joy impossible to anyone but a true
craftsman tremendously interested in his work, we might also add, his
environment.

Naturally, present-day conditions must modify the struggle for existence.
They may mar our best aim at times. Yet some few have worked wonders even
in this age. To mention but two instances, W. De Morgan and the Martin
brothers, is to tell of high endeavour and great achievement. But we must
not expect to get rich that way.

Pottery is an exacting and difficult craft, abounding in as many trials
and disappointments as excitements and rewards. Its true devotee must
suffer. Yet the delightful tale of Palissy’s heroic battle should hearten
the more fortunate student of to-day. It is good to read of the spirit in
which Wedgwood, scientist though he was, approached his work. In a trade
catalogue he says, “A Competition for Cheapness, and not for Excellence of
Workmanship, is the most frequent cause of rapid Decay and entire
Destruction of Art and of Manufacture.” “Beautiful Forms are not to be
made by Chance and they never were made nor can be made in any kind at
small expense.” Such sentiments rarely emanate from the modern commercial
pottery.

Tradition, except the traditions of flawless glazes, certain soulless
results, and commercial cheese paring; seems dead perhaps, but it will
surely come to life again. To see the potter “thumping his wet clay,” and
seated at the wheel of ancient lineage, conjuring forth a wealth of
gracious shapes, is to renew one’s faith in the ultimate survival of
simple honest handicraft even in this machine-ridden age. Masterpieces
were never conceived in factories, and when we make pots primarily for
love of them, not to sell them, we shall begin to beat back the
manufacturer of debauched “Art” pots into that domestic and hygienic realm
wherein his efforts are particularly admirable and effective. A craft that
teems with such an endless variety of beautiful objects for such countless
uses can never remain for all time the hand-maiden of commerce.

[Illustration: Hollowing the Ball]



                               CHAPTER II

                            CLAYS AND PASTES

  “It is the Art which gives the value, and not the material.”

                                                --DRESSER.


Clay being the chief material used by the potter, it demands a description
which, without being too technical, will give from the start a clear idea
of the nature of clays or pastes in general use.

It would be a needless complication to enter here into a discussion of the
chemical analysis of bodies and materials. Whilst the chemist can and does
determine with exactitude the relative quantities of each component, he
cannot yet, let us perhaps be thankful, lay down with the same certainty
the structural and molecular changes all these compounds will undergo in
the fire. The old potters’ rule “of thumb” or, rather, common sense and
experience, still count for something.

Clay is the word generally applied to the natural article when used
without preparation, or after picking and washing. Paste is the term used
for all composite bodies that have been through a complicated process of
washing, grinding, mixing, and sieving, or even fritting, according to
the desired quality of the ware for which it is required. Natural clays
range from the pure white and very infusible kaolin, containing only
alumina and silica with a very small percentage of alkalies, to the impure
grey, red, or brown clays, containing, along with alumina and silica,
magnesia, potash, soda, iron, lime, and carbon. Kaolin is used with China
stone (a combination of felspar and quartz) to make porcelain, the finest
and hardest paste known to potters. It has a very hard white translucent
body, only slightly vitreous at the highest fire (around 1700°
Centigrade).

From this, the highest grade, we have almost insensible gradations to
common earthenware. Old English and French porcelain were compounded of
clay, sand, and alkalies ground together to make a frit, re-ground and
mixed with a stiffening material (in English porcelain, bone-ash), to
support the vitreous matter in the intense heat. The finest earthenware
does not differ greatly in its formula from soft porcelain, but it is not
so hard or transparent. From this the scale descends to where the presence
of lime or iron in the body colour it and render it easily fusible, so
that at any great heat it turns black and collapses to a slag.

Clay on being dug up is usually weathered in the open, and dried and
broken up and the greater impurities picked out. It is then thoroughly
mixed with water in a blunger and passed through a succession of sieves
until all foreign matter and impurities are left behind and it is the
consistency of cream. This was formerly done by hand, the clay being raked
into a thick “slub” and washed through a series of tanks until all
impurities had settled, leaving only the fine clay in suspension. It is at
this stage that any additions are made to form a paste. The modifying
ingredients, ground and sieved to the requisite degree, are thoroughly
incorporated with the slip, which is allowed to settle. The clear water on
top is siphoned off and the paste dried sufficiently to handle. The modern
method of preparation is to force the slip through a series of straining
bags which remove most of the water and leave it stiff enough to work.
Some of the hard pastes are so stiff or short that they require soap water
to give plasticity, but usually after a thorough wedging it is now ready
for the thrower.

Generally speaking, kaolin, China clay, ball clay, pipe clay, China stone,
felspar, flint, quartz, sand, lime, chalk, and calcined bone are the
ingredients of most modern pastes. These supply the alumina, silica, lime,
potash, and soda, with traces of iron and magnesia, that are found in all
clays when analyzed. Carbon is only present in impure bodies fired at a
low heat.

Of these materials the clays rich in alumina and silica, such as kaolin
or China clay, form the body-giving substance. The felspar or China stone
furnish the fluxing ingredients for fusing and binding. The flint or bone
supplies the stiffening matter for supporting and retaining the shape of
the object in the fire.

Porcelain, though differing so widely in appearance and texture from the
coarse mediæval earthenware or the pottery of the ancients, is found to
have a distinct relationship when all these bodies are submitted to
analysis. Much of the difference in bodies, apart from the impurities,
lies in the temperature of the fire to which it has been submitted. At a
low temperature such constituents as lime and iron are not much affected,
but at a greater heat they act as fluxing agents.

To generalize upon a complex and difficult subject one might say that
porcelain, both hard and soft (pâte dure and pâte tendre), is
characterized by its pure white colour and by extreme hardness of body and
glaze with transparency; fine stoneware by a very hard, opaque, and heavy
body which may be white, buff, or grey, and salt-glazed or with a fine
hard transparent glaze. Earthenware is softer and mostly opaque. It may
range from something a little softer than soft porcelain to the coarse
“Majolica” with a tin glaze, differing widely in colour of body and
hardness of glaze.

With porcelain and the finest high-fired wares a purity of materials and
uniformity of mass is absolutely necessary. It is here that one may well
call in the aid of the chemist and manufacturer. In any case it is
advisable to call in the chemist and the manufacturer when working on a
large scale. With a small output, as with all good craftsmen, the
fabrication of a good, reliable stoneware or earthenware paste is only a
matter of patience and hard work. Before commencing to produce finished
work on any scale, repeated experiments with different clays should be
carried out. Notes of all trials, with and without glaze, are invaluable
to the potter.

Rich clays can be stiffened, short clays enriched, and colour modified
without a mass of expensive machinery. Rich, easily fusible clays tend to
_stunt_ or buckle at a high fire. Hard refractory clays often remain
porous and are a fruitful source of crazing and breaking. The addition of
flint or fine washed sand, finely powdered _grog_, or _pitchers_, or even
refractory China clays, in quantities varying from about 5 per cent to 20
per cent, but settled only by repeated trials, will stiffen up or open out
rich clays inclined to warp or burst. Rich fusible clays added to hard
clays may stop the crazing, or the fusing point may be lowered by the
addition of spar. Stiff gravelly clay will require finer sieving or
repeated washing to rid it of some of the grit or sand. Rich greasy clays
are better when not too finely sieved, but this point is of course
dependent on the class of work to be undertaken. Slip can be settled in
tubs, the water siphoned off, and then put to dry on plaster bats, or dry
clay, powdered and sieved, may be stirred in until the mass is stiff
enough to wedge thoroughly by hand.

In mixing or modifying without machinery it is sometimes advisable to do
it in the dry state, otherwise some of the heavier materials are likely to
sink and are thus not thoroughly incorporated with the body. The dry mass
when well mixed is wetted enough to be wedged. When the body is coloured
and a white ground is indispensable, an “engobe,” or dip, of white clay
slip must be resorted to.

These processes are certainly tedious, but that will not deter a craftsman
searching for the right clay in which best to shape his ideas. To the
craftsman working alone it is the only way by which he can accommodate his
clays to the various necessities of throwing, casting, or modelling. Each
process will require a slightly different nature in the clay if the finest
results are to be obtained.

Although in this craft book we shall not approach porcelain, a good, hard,
true-ringing body with a tough well-fitting glaze should be a _sine qua
non_ with all craftsmen; and it is only in the fire that any true idea can
be gained of the important influences clays and pastes have on the
finished work. Here we have tried to indicate the chief characteristics of
clays and to make clear the inevitable tendency of all potters who seek an
imperishable medium for their craft towards a purer body and a higher
fire.



                              CHAPTER III

                              BUILT SHAPES

  “Every moment think steadily: to do what thou hast in hand with
    perfect and simple dignity.”

                                           --M. ANTONINUS.


With good plastic clay and with the aid of a few simple tools, the fingers
can fashion shapes of considerable diversity and some refinement. In
elementary schools this is by far the best method of teaching the
beginner. In any case the student who has no knowledge of clay work would
do well to start by building a few shapes in the manner still used by
primitive peoples.

The clay, which must be in good condition and not _short_, is rolled out
on a wet plaster slab or some non-sticky surface, into ropes of something
less than half an inch in diameter for small shapes. (Fig. 1.) The best
way to commence is to knead up a double handful of soft clay until
thoroughly mixed, ball it, and then form a stumpy cylinder, gradually
elongating by rolling out on the bat. Too much pressure will flatten the
rope and there should be a distinct pull or stretch on it in addition to
the downward pressure, varying as necessary to insure even thickness. As
the rope becomes thinner the fingers should be held diagonally to avoid
ridges. This rope should be fairly firm and yet bend easily without
cracking. With a little practice, long pliable rolls can be easily and
rapidly produced and then a start is made with the base. This is coiled as
in Fig. 2, pressed flat, and welded together. It is finished both sides
before commencing the walls of the shape. These are coiled round and up,
each ring being pressed firmly on the one below, care being taken to avoid
air cavities which may blow out on firing. The top is levelled off and the
sides welded together and smoothed with the fingers. (Fig. 3.)

[Illustration: FIG. 1--ROLLING OUT CLAY.]

[Illustration: FIG. 2--FORMING COIL FOR BASE.]

[Illustration: FIG. 3--WELDING & SMOOTHING THE SIDES.]

At first, simple and almost straight-sided shapes should be attempted;
each ring may be added separately, while the finishing should not be
unduly prolonged. As the technique improves, curves with slight returns
may be attained. Where the size is so great as to prevent finishing at one
sitting, it can be very carefully reversed; this will allow the base to
harden and still keep the top moist for further coiling. With big pieces
much attention must be paid to the correct shaping when coiling, otherwise
the finishing will be laborious and quite possibly useless. Large shapes
with difficult curves are best built in two sections or parts and then
carefully welded together. To keep the parts damp during prolonged
operations, use water blown from a spray diffuser.

Ash trays, bulb bowls, flower pots, salt cellars, and ink wells are a few
of the things that are suitable to be made by this method. They may be
decorated with incised lines, raised-ornament handles, and feet.
Additional interest is obtained by slight banding, or the incised lines
filled in with a coloured clay pressed firmly in when the shape is tough.
Although built forms may be quite highly finished, it is obvious that any
elaborate decoration is out of place on shapes that by their origin must
be simple and somewhat heavy. Enough has been said to indicate the
process. For its logical development and suitable enrichment we must study
the work of primitive peoples. For its possibilities we must turn to the
vast jars made even to this day in Spain.

[Illustration: FIG. 4--ATTACHING THE FOOT.]

With great care and much taste pieces can be pinched and welded together
into delightful forms, best shown in the refinements of the Cha Noya
pottery of Japan. This pinching must be done carefully and above all
sympathetically. To those that know or feel the possibilities of the clay
it will respond readily. Much more taste and judgement is required in the
making of a really satisfactory pinched shape, than is needed in forming
one with coils. Square, polyhedral, or irregular shapes other than
circular may be _stuck up_ or pieced together in the following manner:
Upon a table nail two strips of wood one quarter of an inch thick, ten or
twelve inches apart. Sprinkle between the strips with flint or fine sand
and batter out some soft clay thereon. Scrape the surplus clay off with a
straight-edge and then roll the clay between the strips flat with a
rolling pin. Upon this thin slab mark out the sides, base, top, etc., of
the shape to be built. Run a thin knife round each shape, but do not cut
quite down to the table. Cut along the inside edge of each strip to allow
the whole slab to contract evenly and allow it to toughen slightly.
Carefully remove and reverse the slab and separate the pieces, being
careful not to distort the shapes in the process.

The shape must be stuck up before the pieces become brittle or too stiff
to bend. Roughen each opposing edge and moisten with slip, that is, clay
mixed with water to the consistency of thick cream.

Press the edges firmly together and weld well each joint with soft clay.
(Fig. 5.) This operation should be most thorough, as any weak joint will
inevitably open when fired. Lids should be cut slightly larger than the
shapes they have to fit and sandpapered true when dry. Sharp edges and
angles should be smoothed with the fingers before the shape gets hard.

[Illustration: FIG. 5--“STICKING UP” FLAT-SIDED POT.]

The chief pitfall to avoid in this process is a hard wooden look. The
ductile plastic qualities of the clay should be remembered and such
additions as feet or handles should emphasize this important point.

Finally, the careful sympathetic craftsman, with infinite patience, by
utilizing all three methods, can build vessels of almost any
shape,--square, round, elliptical, banded, strapped, bossed, fluted, and
embellished with handles, spouts, and feet. Ancient and mediæval pottery
is rich in such forms.

[Illustration: TOOLS FOR CLAY WORK.]



                               CHAPTER IV

                    MOULDING, CASTING, AND PRESSING

      “Our soundes is good, Our shapes is neat,
      Its Davis cast us so compleat.”

                       --From an old bell at Stoke Rivers.


The casting process, employed so extensively in commercial work, is in its
essence mechanical and therefore can never have the spontaneity or
character of thrown work. To-day when the thrower and turner with hand and
eye trained for good shapes is rare indeed, it is often the only method by
which the student can obtain large shapes of high finish for painting or
glazing in transparent colours.

In the process the shape is first designed and carefully drawn on paper,
allowance being made for the shrinkage of the finished pot which may be as
much as 1 in 6 with some kinds of slip. It should be refined in profile
with no returns that may bind or hold in the mould when drying, yet it is
obvious that simple shapes that can be built or thrown by the beginner are
not suitable for casting.

[Illustration: FIG. 6--MANDREL, ROLLED IN PAPER.]

[Illustration: FIG. 7--“ONE PIECE” MOULD FOR BOWL--METHOD OF RELEASING
ORIGINAL.]

The shape correctly drawn, a mandrel, a steel tapering to a point, the
butt wormed to screw on a lathe, and long enough to give some play at
either end, is rolled in stout paper, gummed at the edges, as in Fig. 6.
This is removed and allowed to set, thus giving a paper shell just fitting
the mandrel. Trim this square at the base and stick it upright by means
of a piece of clay on a well-oiled portion of a table. Around this as a
centre is fitted a roll of linoleum, oiled inside and secured with string,
with all its joints caulked with clay. The inside diameter of this
cylinder should be about 1/2” larger than the greatest diameter of the
drawn shape. Enough superfine plaster to fill this is now mixed. To do
this shake plaster by handfuls into a bowl of water until it appears to
refuse more, pour off any surplus water, and stir with a wooden ladle or
the hand, avoiding air bubbles.

[Illustration: FIG. 8--A TWO-PIECE MOULD.]

[Illustration: FIG. 9--POURING IN PLASTER.]

A little practice in casting plaster bats will give the experience
necessary for mixing plaster. When well mixed and a slight thickening is
perceptible, it is poured very carefully into the cylinder, the paper
shell being kept upright in the centre. (Fig. 9.) In about 20 minutes the
surface of the plaster will feel warm. It is now set and the linoleum is
removed. The plaster cylinder, when dry, is fitted on the mandrel, and
this screwed to the lathe head. Two or three chisels are now required.
(Fig. 10.) The rest on the lathe is clamped in a convenient position and a
cutting chisel held as shown (Fig. 11), cutting edge up. The cylinder is
revolved briskly as indicated by arrow, and the shape is roughly hollowed
out. Proceed gradually until the shape begins to emerge, taking care not
to cut too deeply. (Fig. 12.) Towards the finish use the calipers
frequently to check the measurements. At top and bottom about 1/2” waste
is left (Fig. 13 A), turned straight, the actual line of top and base
being slightly grooved in the plaster. The form may be pretty accurately
finished with the chisels and then nicely smoothed with sandpaper. For
this process the rotary movement is reversed.

[Illustration: TURNING TOOL.]

[Illustration: FIG. 10--CHISEL POINTS.]

[Illustration: FIG. 11--POSITION OF TOOL.]

The shape is now removed from the lathe and is ready for moulding.

With a kick wheel having a removable head the mandrel can be screwed on
and the block turned down in an upright position. The difficulty of
steadying the tool renders this method somewhat unsuitable for this
process, where perfect symmetry and a high finish are required. The
plaster should not be so dense for turning on the wheel or the kicking is
apt to become very arduous and this tends to dislocate the set of the
spindle. One of the best of ways is to draw a quantity of shapes, cast
their blocks, and turn them on a hired lathe, preferably run by power.

[Illustration: FIG. 12--PARTLY TURNED BLOCK ON LATHE.]

The finished shape is now well lathered with parting or stopping. This is
made by boiling 1 lb. soft soap, 1/4 lb. Russian tallow, and a small piece
of soda. Another stopping is made by dissolving 1 lb. soft soap in 1 qt.
water and stirring in 1/4 pt. paraffin oil. Several coatings may be
necessary to impart a waxy surface. When no longer absorbent, it is dried
and slightly polished with a bit of cotton waste. At the finish the form
should be clean, smooth, glossy, and non-absorbent.

With simple shapes, as in Figs. 7 and 8, a one-piece or a two-piece mould
can be made, and here the bottom waste is not necessary, but with any
return or foot a three-piece mould will be required. The waxed shape is
now divided perpendicularly exactly in half, by a pencil line. (A, Fig.
13.) It is then laid on its side and bedded in clay up to the pencil
lines, the clay being sloped slightly down from the marks. (F, Fig. 13.)
Box in now with well-soaped boards tight against top and bottom but
allowing about 1-1/2” at sides. Wipe the shape over with waste dipped in
olive oil but leave no surplus oil on the surface. Plaster well mixed as
before is poured in until about 1-1/2” to 2” above the greatest projection
of the shape, great care being taken to avoid or dislodge air bubbles. (B,
Fig. 13.)

When the plaster is set but still warm, the shape is removed and the side
of the plaster that rested on the clay trimmed flat and several joggles or
natches are made. (C, Fig. 13.) The shape is now replaced exactly as cast
and the new surfaces treated with parting and the whole slightly filmed
with oil as before. Great care must be used, for any oil on the actual
surface of the mould spoils the suction of the plaster at that spot. Box
in and then cast just as before. This gives two halves with waste top and
bottom.

[Illustration: FIG. 13--A: METHOD OF DIVIDING. B: MOULDING 1^{ST} HALF.
C: MOULDING 2^{ND} HALF. D: A METHOD OF SECURING BOARDS. E: MOULDING BASE.
F: MOULDING 1^{ST} HALF.]

The shape is now placed on the lathe and the bottom waste turned off, the
base of the shape being slightly hollowed. The creator having arrived so
far successfully may now unbend and scratch his mark on this new surface
before well waxing it.

Dowels are cut in the waste of the two halves as shown, the fresh parts
soaped, all fitted together and slightly oiled, then boxed in as in D and
E, Fig. 13. Plaster about 2” thick at the thinnest part is poured on and
the mould is complete. When set, the shape is removed and the three parts
trimmed on all the outside edges. (Fig. 14.) The three pieces are
assembled, firmly tied up to prevent warping, and thoroughly dried.

If preferred, the mould can be made cylindrical instead of square. This
will give a more even suction to the slip and may be worth the extra
trouble. For casting purposes a refractory clay containing a good
percentage of China clay, maturing at about 03-01 but remaining perfectly
white and porous, will be required.

Slip for casting is made thus: Clay, picked or broken into small pieces,
is thrown into a bucket of warm water well slubbed up by hand and passed
through a fine sieve (No. 80) with the aid of a stout brush and thinned
to the consistency of thick cream. This should be matured for some days,
frequently stirred, and again sieved before using. For very small or
fragile shapes, a finer sieve (120) is advisable. The mould, quite dry and
clean, is now slightly moistened with a scrupulously clean sponge and
water, the parts assembled, corded, and firmly wedged, leaving the top
free as in Fig. 15. The slip, thoroughly stirred, is poured in very gently
to avoid bubbles. With awkward moulds, a tube or funnel should be used to
prevent splashing. If the mould be placed on a whirler and turned to and
fro, it will prevent the heavier matter in the slip settling too quickly.

[Illustration: FIG. 14--THE THREE PARTS OF THE MOULD.]

As the slip sinks in the mould, the subsidence being due to the absorption
of the water by the plaster, the mould should be continually filled up.
After a few minutes the mouth is scraped free to test the deposit. When
this is thick enough, varying, of course, with the size of the shape, the
slip is poured out into another bucket. An unorthodox but often useful
trick for strengthening long necks is to slide a piece of glass over the
mouth and reverse the mould for a minute or so. The neck full of slip thus
allows a slight extra deposit on the part that most needs it when we come
to finishing off the lip.

[Illustration: FIG. 15--MOULD READY FOR SLIP.]

[Illustration: FIG. 16--FREEING TOP.]

Let the mould drain a little over the slip bucket and then reverse to dry
slowly. When the wet look has disappeared from the surface of the slip,
scrape the top free and run a knife around to prevent sticking as the
shape contracts. (Fig. 16.) In a few hours it will be dry enough to permit
of the sides being eased off and the shape left to dry on the base. (Fig.
17.) When tough enough to handle with safety, the waste and cast lines are
trimmed and finished off, any air bubbles or holes broken down and filled
with clay scraped from the waste or base. If this finishing is left until
the shape be dry, it is impossible to hide such defects. The greatest care
must be exercised in handling cast shapes, as they are exceptionally
fragile.

[Illustration: FIG. 17--SHAPE READY FOR TRIMMING.]

When quite dry, the whole form should be carefully gone over with a very
fine sandpaper. A superfine surface should be imparted by rubbing with the
hands. When using transparent glazes, as with under-glaze painting, it is
essential that all scratches be removed, and especially must all sharp
edges be eliminated on neck or shoulder, for the glaze running away from
these places imparts a hideously cheap look to what otherwise may be a
fine shape. All these points having received attention, the date is
scratched on the bottom of the shape and it is now ready to biscuit.

Generally speaking, it will be found that slip the consistency of cream is
right for casting, possibly thicker for big open shapes, and after the
right proportion is settled it is as well to test what it weighs to the
pint.

As will be readily seen, this process, whilst open to many objections,
lends itself to shapes that are refined and delicate and to those that
have flutings or raised ornament. Such decorations, or the spouts of jugs,
may be modelled in wax on the plaster shape before casting and appear in
reverse on the mould. Designs may be scratched on the mould or shape and
show as a delicate tracery beneath the glaze. All these things, however,
add to the difficulty of casting and should be approached by degrees and
with restraint. For in unskilled hands the process lends itself to
soulless and mechanical repetition.


                                PRESSING

Moulds having moderately wide mouths enable the potter to press his shapes
instead of cast them. This method in expert hands is even quicker than
casting and has the advantage of imparting a sturdier look to large
shapes. Pressing is also resorted to for those shapes to which it would be
difficult for the slip to obtain free access.

[Illustration: FIG. 18--ROLLING OUT CLAY.]

For the ordinary three-piece mould the procedure would be thus: The clay,
well wedged and quite plastic, is rolled out as described in Jigger and
Jolley work, to a suitable thickness. (Fig. 18.) Butter cloth or fine
linen will do instead of leather to roll the clay on. The insides of the
three parts of the mould are sponged and pieces of the thin rolled clay
roughly cut to fit them. These pieces are now fitted and well applied to
the three parts by dabbing with the damp sponge. A soft close-textured
sponge, or a soft felt dabber, is best for this operation. When closely
setting, the edges are trimmed and given a slight bevel. The top is cut
straight. Then the mould is assembled and firmly tied. Some of the waste
clay is rolled into thin _ropes_. With the bevelled edges slightly
moistened, these ropes are firmly wedged into the two side junctions and
round the base. Where the mouth is large enough for the insertion of the
hand this is not a difficult operation. If it be narrow, the two halves of
the mould may be tied up and the joints welded together before they are
assembled on the base. A coil of clay can then be placed on the edge of
the base just clear of the two sides which are now fitted over and tied
up. Then a stick sponge is used to join up the base to the sides. (Fig.
19.) After a little while the shape is fit to be removed and is finished
in the usual way.

Nothing can rival large thrown shapes for vigour or variety, but
unfortunately they are not always within reach of even the good craftsman.
Then this method offers the least objectionable substitute for them and in
clever hands is capable of many fine results.

The following method is used to mould handles or simple applied ornament.
Handles, feet, masks, etc., are usually pressed and stuck on the dry shape
with slip. To mould them some skill is necessary if the press is to be
quite accurate and free from twist or ugly seams.

[Illustration: FIG. 19--SECTION OF A MOULD. STICK-SPONGE WELDING BASE TO
SIDES.]

One way, when the handle or foot is symmetrical, is to cut the model
exactly in half. This must be done when the model is tough enough to
handle without bending or distorting it. One half is laid cut side down
upon a sheet of glass, and surrounded at a convenient distance with clay
walls. Plaster is now poured on to form one half of the mould, and
allowed to set. It is then removed and the smooth surface joggled and
claywashed (brushed over with claywater). The other half is then very
carefully applied to the half still embedded in the mould, the walls built
round and the other part of the mould cast. Then all is trimmed up and a
groove run round the form as shown. (Fig. 20.) For pressing, the form is
well filled with clay and the two halves of the mould strongly pressed
together. Any surplus clay will squeeze into the groove and when tough
enough to remove the whole is “fettled” and finished before drying and
sticking up.

[Illustration: FIG. 20--HALF OF MOULD FOR PRESSING HANDLE.]

With care and practice this method is possible: Build walls and pour in
enough plaster to form one half of the mould. Before it stiffens, very
carefully press in the handle or ornament just up to the halfway line and
allow to set. Joggle, claywash, and cast the second half. Finally, when
the object is of any size, clay walls may be used as described in the
chapter on Figurines.



                               CHAPTER V

                         JIGGER AND JOLLEY WORK

      “Earth I am, et is most trwe, desdan me not, for so ar you.”

                                    --From an old platter.


Dishes, platters, and to some extent bowls, are usually made on a _Jigger
and Jolley_. The jigger has a revolving head, fitted to receive moulds.
The jolley has a pivoted arm to which different profiles may be clamped.
In factories these things are complicated and go by power, but in a studio
where the output of platters and dishes is likely to be limited something
simple will do. Where the wheel is strong, well-hung, and fitted with a
removable head, a contrivance as shown at Fig. 21 can be fitted by any
carpenter, that should serve all purposes.

The vertical supports of the jolley arm should be quite rigid. The arm
itself must so pivot that the face of any profile screwed onto it will
cross the head of the jigger, or wheel if one be used, through the centre.
In other words, the cutting profile must form a diagonal of the circular
head. Then, too, it must be hung at a height sufficient to allow a fairly
thick block of plaster being used for a mould.

[Illustration: FIG. 21--MAKING A DISH.]

When making these moulds, the slotted wheel head or the jigger head is
removed and soaped or oiled. Then a circular block of plaster is cast to
fit. This may be done with the aid of a roll of linoleum, much in the way
described in casting. The paper cone will, of course, be replaced by the
wheel head, bedded face up in clay. This plaster block has to be moulded
to the exact size of the dish or plaque required. To do this a profile of
zinc is necessary. The true section of the dish is drawn full size, and
profiles giving one half of the back and front are traced on a stout sheet
of zinc. The zinc is roughly cut to shape with shears and then finished
with a file to a chisel edge (see cut). The two profiles are then firmly
backed with shaped wooden forms, slotted to screw onto the arm of the
jolley. The profile giving the _face_ of the plaque is securely adjusted
in a horizontal position, the inner point, giving the centre of the
platter, being exactly over the centre of the jigger head. The plaster
block, which should be turned down before it sets hard, is shipped back
into position, the jigger revolved and the profile gradually pressed down
until the true section is obtained, _i.e._ when the profile is exactly
horizontal again. The mould is now removed, trimmed at the sides if
necessary, and set apart to dry. It is then ready to use. The mould is
slipped into position and revolved to insure even rotation. Then the
profile giving the back of the platter screwed onto the arm and both
adjusted until the stop allows the profile to rest at just that distance
from the mould required by the thickness of the platter. (Fig. 22.)

[Illustration: FIG. 22--PROFILE IN POSITION ABOVE PLATE MOULD.]

The arm is then swung clear of the mould, which is well sponged with water
to receive the clay. This is carefully wedged and then rolled out or
batted flat on a piece of leather until it is a little thicker than the
thickest part of the platter (see Fig. 23). The slab so made is smoothed
with a palette knife, taken up, leather and all, slapped onto the mould,
clay side down, and the leather removed. The clay is now well dabbed down
with a wet sponge or dabber, to take out all wrinkles, pressed firmly onto
the mould and the waste cut off.

[Illustration: FIG. 23--CUTTING EDGE OF PROFILE.]

Now the jigger or head is set spinning, the jolley pulled over it, and the
profile gently pressed into the clay. Water is used freely to prevent the
profile sticking, and as it becomes clogged the clay is removed. The
turning is continued until the profile comes to a stop on the rest. Holes
that may appear should be filled up before the finish, at which time the
surface should present a smooth unscratched appearance. The shape is
allowed to dry on the mould until tough enough to be slipped face down
onto a perfectly flat slab dusted with fine sand or flint to prevent
sticking. In this position it is left to dry, when the edges are nicely
trimmed with fine sandpaper.

For bowls the process is similar, but the mould here gives the outside and
the profile the inside as in cut. (Fig. 24.) If made on the outside, they
split before they can be removed. With small bowls the clay is wedged and
a lump pressed into the mould by hand. With large bowls requiring a deep
foot this must be turned separately and stuck on after the bowl is removed
from the mould.

[Illustration: FIG. 24--BOWL.]

Where a jigger and jolley is not available, plates and bowls may be
duplicated as follows: Place the plate bottom up on a well-soaped surface
or a piece of glass. Should the plate not lie quite flat, caulk the
apertures with clay, then all round and distant one and one half inches
from the rim, build clay walls, or fix a containing band of linoleum, of
sufficient height to allow plaster being poured in an inch and a half
above the base or foot of the model. Mix fairly stiff plaster and pour in.
Let it set, and then remove walls and the model. This gives a mould of the
reverse of the plate or bowl. The mould is thoroughly dried before using
and then sponged with clean water. Clay of the desired thickness is then
rolled out as described and applied to the mould and dabbed flat with a
sponge or dabber. The finish is imparted with the fingers and the surplus
at edges trimmed with a knife. When tough, the press is slipped out and
reversed to dry on a piece of sanded glass. Where there is a rim to the
plate or bowl, this should be filled in cleanly with clay before the whole
is pressed. It is of course impossible to mould thus bowls that possess a
deep or under-cut foot.

[Illustration: FIG. 25--PLATE MOULDED TO GIVE BACK.]

[Illustration: FIG. 26--MOULD. TO GIVE FACE OF PLATE.]

[Illustration: THE KICK WHEEL.]

[Illustration: Egypt. B.C. 2000 ANCIENT EGYPTIAN POTTER.]



                               CHAPTER VI

                             THROWN SHAPES

           “The lyf so short, the craft so longe to learne.”

                                                --CHAUCER.


The wheel is the true fountain head of all beautiful shapes, and the
student who would become a potter cannot get “on the wheel” too soon.
Throwing, sometimes _spinning_, is the term applied to the making of
shapes on the wheel. Interesting and really fine pots may be built or
cast, but the ultimate appeal rests with the thrown shape.

Unfortunately, a complete mastery of throwing is not to be gained by a few
spasmodic wrestles with the wheel. It comes only with long hours of
concentrated effort. Having watched an accomplished thrower and seen the
full round shapes rise so easily between his dexterous fingers, it is with
a severe shock that one realizes at the first attempt the skill and
practice that will be required before such a desirable proficiency is
attained.

The best kind of wheel is the kick wheel shown in the illustration. With
this the feet, hands, and head work in harmony, accelerating or retarding
the motions as required. It is a not distant relation of the earliest
wheel, which was a heavy head on a short shaft, pivoted in a stone socket.
Set spinning by hand, it was kept revolving some time by its own momentum.
This form of wheel is used even to this day in the near and far East.

Its first development was a secondary wheel and driving band turned by
hand. This led to the wheel shown in the frontispiece and to the kick
wheel and again on to the factory wheel. This in its turn is being
superseded by the steam wheel, which gears onto a running band, the foot
being used to start, stop, and regulate the speed. The two last named were
introduced with the idea of accelerating the production rather than the
improvement of the shapes. No doubt the now primitive kick wheel, much as
used by the potters of the Renaissance, will be found good enough for us.

The tools required for throwing, after the wheel itself is secured, are as
follows: a thin copper wire twisted between two bits of wood, a pricker,
a fine soft sponge, another bit of sponge tied to a stick, one or two
modelling tools and a rib (see Fig. 27).

[Illustration: FIG. 27--1, “Rib”; 2, Modelling Tools; 3, Pricker; 4,
Sponge; 5, Wire; 6, 7, and 8, Shaving Tools; 9, Leather. THROWING &
SHAVING TOOLS.]

The clay is first knocked up into shape ready for the throwing. To do this
it is _wedged_, a fair-sized piece being taken in both hands and thrown
violently down on the bench, cut across, and smashed together again. This
process is repeated until all air bubbles are expelled. This is
ascertained by cutting with a wire. The finger is then passed across the
surface to tell if it is well together, and not hard and soft in streaks.
If, as must happen in a small pottery, the clay is out of condition, it is
best remedied by cutting it with the wire into thin slabs, piling them
criss-cross and then wedging the mass. If still streaky, it can be quickly
tempered, piece by piece. A double handful is torn across, wedged together
at a different angle between the hands, re-torn, and re-wedged, until hard
and soft are welded indistinguishably together.

This thorough wedging is essential, as with beginners a small lump or
bubble will usually be sufficient to bring about the collapse of the
shape.

The clay being thoroughly wedged is rolled into balls of a convenient
size. For first practice they should be on the small side and moderately
tough, as this allows a little more play before the ball becomes too soft.
The wheel is now started revolving from right to left (see cut). The head
being clean, the ball is thrown smartly onto its centre. The hands are now
wetted in a bowl of water, which is put, together with the tools, on the
shelf to the right. Then gently but firmly, with hands placed as shown in
Fig. 28, the ball is centred. At this stage, perhaps the most critical of
all, the wheel should revolve quite briskly. The hands should be moistened
if inclined to stick and the left hand held steady, the elbow pressed into
the side, the forearm hard on the rest. The right hand has more freedom
and coaxes the ball into a half sphere. This when dead centred is
elongated, pressed down again, and re-formed into a truncated cone. The
left hand still steadying, the thumb of the right is pressed firmly into
the centre of the top, down and out, to hollow the ball (see page 18), but
stopping short of the lathe head. At this stage the most convenient shape
to form is a cylinder, its walls gradually diminishing upwards with a
little fatness at the rim. To do this the wheel is slowed down a little
and the fingers of the left hand inserted. The sides are felt and gently
pulled up, between the left index finger and the two first fingers of the
right hand, gradually higher and thinner, always endeavouring to keep the
walls at an even but slightly tapering thickness. (Fig. 29.)

[Illustration: FIG. 28--CENTRING.]

[Illustration: FIG. 29--PULLING UP.]

At first two fingers only will be inserted, but as the shapes grow in size
the whole of the left hand will gain admittance. Then the perfect cylinder
may be modified to almost any required form. With narrow-mouthed shapes
the opening must be kept as small as possible, for the clay once pulled
out it is difficult if not impossible to compress it again. The centring
and hollowing once mastered, the chief difficulties to avoid are getting
the bottom of the walls too thin before the top is pulled up, and making
the top wavy and irregular. If the latter happens, it should be at once
cut back with the pricker, which is also used to test the thickness of
the sides and base.

When the shape has been pulled up to the required form and is sufficiently
thin, the top is smoothed and fattened between the fingers. This not only
imparts a look of substance to the vase and takes away any _cast_ look,
but gives strength where it is most needed. The inside, if wet, can be
cleaned out with the stick sponge and the outside lightly smoothed with
the other sponge. For the insides of bowls or wide-mouthed shapes, a rib
of slate or zinc (see Fig. 30) will be useful for obliterating ridges. The
last operation is to pass the wire, held firmly to the wheel head, beneath
the pot and lift it off and place it on one of the pot boards or plaster
discs. (Fig. 32.)

[Illustration: FIG. 30--“RIB” OF METAL FOR OUTSIDE. “RIB” OF SLATE OR
BONE FOR INSIDE.]

The first primitive forms are far better left frankly for what they are.
Afterwards when bigger and more finished shapes are attempted, they can be
thinned and refined with the aid of the rib and a modelling tool, a
considerable finish being put on before they are removed from the wheel.
With bowls or large shapes it will be found impossible to lift them off
without destroying the shape in some degree. For these wood or plaster
discs will be required. The plaster bats need soaking in water before use
and the wood must be three-ply to prevent warping. These discs are centred
on and firmly stuck to a layer of clay run out on the wheel head, and when
the pot is finished they are removed with it.

[Illustration: FIG. 31--FINISHING WITH “RIB”.]

[Illustration: FIG. 32--PASSING WIRE UNDER TO REMOVE.]

All this sounds very simple, but the beginner will do well first to
practise and master centring the ball. Until this be done, the rest of
the work is worthless. After this must be practised the pulling up, the
pressing down, and the forming of truncated cones, then hollowing the ball
and pulling up into a cylinder. A true cylinder accomplished, it is easy
to branch out into simple wide-mouthed vase forms. As the skill increases,
shapes with double curves and long or narrow necks may eventually be
achieved. Throwing to a set copy induces a necessary concentration at this
stage, but once a mastery is attained, shapes seem to suggest themselves.

A small mirror placed so as to reflect the true form will be found of
great service. When pairs or several duplicates are required, a drawing of
the exact profile must be made and a “rib,” of zinc or slate, filed to
fit. Without such a guide the matching up is well-nigh impossible.

[Illustration: FIG. 33--STAGES FROM CENTRED BALL TO TURNED SHAPE.]

When watching a clever thrower in a factory making some difficult and
probably horrible vase, it is intensely interesting to see the fine forms
evolved in the process. To the artist the impulse to stop him is almost
irresistible. It was there that the old masters showed their wisdom and
restraint. They stopped at the right moment and none of their shapes
descend to the merely clever.

There is a nobility about a large vase lacking in a small one. Once the
appetite be whetted for big pots the desire for size seems insatiable. The
only way out, except for the born thrower, is the two- or three-piece
vase.

The Chinese were masters of this as of every other process and we find
that they frequently made vases of quite moderate size in two or three
parts, sticking the pieces together with consummate skill. This process,
however, should never be attempted until considerable proficiency has been
gained in throwing to a drawing, for in any but expert hands it is doomed
to failure. The shape must be carefully drawn out on paper and the
sections marked off and then thrown exactly to size. Any deviation means
endless trouble, with eventual disappointment.

For this difficult work the student unable to devote a lifetime to
throwing will find a removable wheel head a necessity. Then a slotted one
can be screwed on which will allow a plaster disc to be shipped back into
exactly the same position, thus saving the difficult task of re-centring.
For prolonged operations these plaster discs require to be shellacked to
prevent the work leaving.

[Illustration: FIG. 34--ASSEMBLY OF THE PARTS.]

To start with a shape as shown in the illustration might be attempted.
(Fig. 34.) The drawing made full size is hung in full view. Then the gauge
is set to the exact width of the joint. The bottom half is first made,
being cut square and true with the pricker. The drawing is reversed and
the upper half thrown, the neck being at the bottom with a fair amount of
waste beneath. When each part is trimmed accurately to measure, they are
put aside to toughen.

The top portion will stiffen just as required, leaving the neck still
moist. The bottom half will need watching to prevent the upper edge drying
before the base gets firm enough to support the top when attached. A damp
cloth lightly wrapped round it will help to insure the ideal condition for
sticking up, which is a gradually diminishing state of toughness from the
base up to lip, the junction of the parts being in exactly the same state.

When fit to handle, the top half is cut through at the lip, allowing a
trifle for finishing off. Next the bottom half, still firmly fixed to the
bat, is slotted back into its original position on the wheel. The flat
surfaces that have to be applied and stuck are now very carefully and
slightly roughened, then painted with thick slip made from the same body.
These two wet edges are now applied and gently and firmly pressed into
position, the wheel being slowly revolved to see if the two halves run
true. When well together and apparently sticking, a little wedge of soft
clay can be carefully run in all around the joint. This operation should
be very thorough, and the clay wedge must be carefully welded into the
sides of the joint. This is finished off on the outside with the rib and
the inside very lightly smoothed with the fingers. During this process the
top should be covered with a soft wet cloth, then when the joint has been
made good and will stand the slight strain, the lip is finished off in the
ordinary way. With three-pieced shapes the lip can be finished before
sticking up, as the last part is thrown in its right position. If at any
time the shape shows a disposition to leave the plaster bat, it should be
stuck down with wet clay. The toughened shape can now be turned down in
its upright position, cut off the bat, and the base hollowed in a chuck
(see next chapter).

[Illustration: India. B.C. 2000]



                              CHAPTER VII

                           TURNING OR SHAVING

            “A sharp spear needs no polish.”--Zulu proverb.


The turning or shaving operation takes place when the green shape has
dried to a _leathery_ condition. It consists in shaving the sides and
hollowing the base until the thickness is uniform. The shape is thus made
much lighter and rendered less liable to crack from unequal contraction.
At the same time a fine finish is imparted to the surface.

One of the handiest tools for shaving is shown in Fig. 27, no. 6, but a
piece of hoop iron bent at right angles and shaped with a file will serve.
Small hollows can be finished with a modelling tool. An old piece of
leather will close up and finish the surface. In factories a horizontal
lathe is usually employed, the shape being fitted over a _chum_ or
_chuck_. Skilled men can turn shapes down until they are scarcely thicker
than tin, but this, it is needless to add, is an abuse of method even with
porcelain, and quite out of place with stoneware or earthenware. All that
is necessary is to trim the thick sides, hollow the base, and smooth the
surface. (Fig. 35.)

[Illustration: FIG. 35--SECTION SHEWING TURNED & THROWN WALL OF A
SHAPE.]

A simple way to arrive at this is to throw on the wheel a chuck of stiff
clay to fit the shape, wide-mouthed ones being fitted over and ordinary
shapes within the chuck. (Figs. 36 and 37.) A piece of soft linen is
placed over this chuck to prevent sticking and the shape fitted and
centred. When spinning quite truly from right to left and steadied with
the left hand, the tool should be gently applied as shown in the
illustration. Hollow the base and then shave the sides, turning all down
very gradually and improve the outline as much as possible in the process.

[Illustration: FIG. 36--SHAVING THE BASE.]

[Illustration: FIG. 37--SHAVING THE SIDES.]

Care must be taken with the base. If it is not quite true it should be
sandpapered to stand flat. A little experience will soon show when it is
in the best state for shaving. If the clay is too soft, the tool jumps,
forming ridges, or possibly cuts deeply into the form. If it is too dry,
the surface crumbles and the pot is liable to break. When turned in the
right leathery condition, the shavings curl off like peel from an apple
and all tool marks are easily removed. A beautiful finish may then be
imparted with the leather.

To end the process the shape is reversed in the chuck. Those most
important parts, the shoulders and lip, are carefully rounded with a piece
of felt and polished with the leather. Properly attended to, this will
save much work and disappointment later on. Then with all holes filled up,
all ridges, bumps, and sharp edges removed, the shape is signed and put to
dry.

For very delicate work in transparent glaze or under-glaze painting, the
whole surface may be gone over with very fine sandpaper and polished with
the hand. This may be done provided the body is a fine one, for with a
coarse body this is apt to leave the surface looking gritty. Some little
practice will be necessary in throwing stiff chucks and centring the shape
securely, but this once mastered, the method here described will be found
to be expeditious and satisfactory for turning shapes.

A proper regard for process points to the desirability of leaving built
shapes without a high finish.

Yet they also, if built carefully and stoutly, may be turned down in the
above manner. The building up and turning down is somewhat tedious, but it
is sometimes the only way by which a craftsman can obtain large shapes. A
rather more simple process is to centre the shape upon a whirler and turn
down with a sharp wire tool, finishing off lightly with a sponge and soft
leather.

To accomplish this satisfactorily the shape must be fairly soft, as there
can be no quick spinning motion to enable the tool to cut cleanly as in
the chuck or the wheel. When the head of the whirler is of plaster, it
should be well soaked in water and the centred shape stuck down with soft
clay. The hand holding the cutting wire tool must be held steady at a
fixed distance from the centred shape and the pot may be sprayed with
water blown through a diffuser from time to time, to keep it moist. Some
clays will not, however, stand much re-wetting.

[Illustration: FIG. 38--POSITION OF TOOLS WHEN SHAVING.]

It should not be necessary to caution the craftsman against angular
profiles, splayed feet, or sharp mouldings. Such features are foreign to
good pottery, however suited to metal or stone.

With taste and judgement the irregular grooving caused by the tool can be
made of high decorative value. In no case should the built shape try to
masquerade as a thrown shape. When the whirler is used to shave down built
shapes, they may be coiled very thick at the base, thus allowing more
rapid work.

The attention must then be concentrated on the profile of the inside. In
this way many shapes that splay out or curve boldly from the foot may be
built, which would otherwise present many difficulties in coiling.



                              CHAPTER VIII

                              TILE-MAKING

  “VI thousand and fourscore of pavynge tiles delivered at Hampton
    Court, for to pave the Kinges new hall at XXVJs. VIIJd. the
    thousand.”

                           --Sixteenth century memorandum.


Tiles may be made of various kinds and sizes, but in every case they show
an inclination to buckle in drying and firing. The larger the tile the
stronger is this tendency to warp. The clay must not be so rich as that
which is used for throwing and should be tempered to counteract the
tendency to curl.

A tile box as shown in Fig. 39, or a variant of it, will be required for
pressing tiles by hand; for plain tiles 5/8” deep, for others 1-1/4” deep,
the size being calculated to allow for shrinking. The sides hinge and the
thumb screws keep it steady on the bench during work. For rough tiles, two
strips nailed to the table will serve, the clay being rolled out between
and cut in lengths as required.

For plain tiles the wedged and tempered clay is batted out into a slab a
full 3/4” thick. The mould is dusted with French chalk, flint, or very
finely sifted clay dust, to prevent sticking, and into it is pressed a
piece cut to fit easily in the tile box, from the slab. This is firmly
pressed into the box, considerable pressure being used. The surplus is
scraped off and the top trued with an iron straight-edge. The knife can be
run round the sides, then with the frame reversed a smart tap on the back
will release the tile.

[Illustration: FIG. 39--TILE FRAME--6-1/2” x 13”.]

Let the tiles toughen and then pile in stacks with flat pieces of clay or
old tile between each corner and a true biscuit tile at bottom and the
top. They can be piled one on the other with sand between or stacked like
bricks with alternate holes for the air to circulate. This retards the
drying, but in any case they must be dried slowly. With plain glazed tiles
a little coarse dust sprinkled over the surface before the tile is removed
from the box, and well pressed in, will give a slight interest to the
surface and take away any mechanical look. If required for painting, the
clay must be very finely sieved and the surface will need careful
finishing by hand when dry. With coarse clay, a fine surface can be
imparted with a flexible broad palette knife.

For raised outline tiles a frame 1-1/4” deep is required. This allows a
plaster bat 5/8” thick to be placed at the bottom. The best way, perhaps,
is to oil the frame and cast the bat in it, removing it when set and
sandpapering the upper surface flat and true. The design for the tile
drawn the exact size on paper is now traced on this surface. It is far
better to sketch it directly onto the slab, but this demands some
proficiency if the surface is to be preserved. The design is then incised
with a firm sharp point, clay squeezes being taken from time to time to
show the progress of the work. The plaster should be wetted to insure easy
working. At the finish the design should stand out in a fairly strong and
deep line--square--not round or angular in section. (Fig. 40.) A
chisel-pointed hard pencil will be found best for finishing. This gives a
clear-cut line, not too round. The bat, sponged clean and porous, is then
placed in the frame and the tile pressed as before.

[Illustration: FIG. 40--A: POINT FOR FIRST OUTLINE. B: DO. FOR FINAL
INCISED LINE. C: SECTION OF INCORRECT CLOISSONS. D: CORRECT.]

Raised outline tiles can be even more satisfactorily made by means of
outlining slip squeezed from a tube or tracer in the same manner that
inscriptions are made on sugared cakes, but this requires much practice to
obtain good results. When glazing, the coloured glazes are applied to the
different compartments with a brush. As the glaze fuses to about one third
of its bulk when dry, it should be applied very liberally.

It will be found that large or elaborate designs are to be avoided, as in
this process they tend to become mechanical and look thin. The old
Spanish and Moorish tiles in this style with jewel-like bits of colour are
excellent guides and might be studied with advantage.

[Illustration: FIG. 41--SLIP TRACER.]

The process of making encaustic tiles is a little more complicated. Within
the frame is placed a well-lathered or soaped plaster bat (or tile) high
enough to allow only a thin layer of clay 1/8” thick being run out on top.
On this when firm the design is traced or pounced. Then with a thin sharp
blade it is cut down vertically to the plaster bat, and the clay removed
until the whole design shows in white plaster beneath (see illustration
42). The face of the clay left must be preserved carefully, as it forms
the surface of the subsequent press.

The bat with clay is now placed on the bottom of the frame to allow a cast
5/8” thick to be made. The plaster and the sides of the frame are slightly
oiled and the plaster mixed and poured in. A soft hair brush will be
useful to dislodge the air bubbles that are certain to hide in some of the
many odd corners. When nearly set, the surface of the plaster can be
scraped flat, and when set taken out of the frame and detached. The clay
is picked out and the whole surface of the design cleaned and trimmed so
that it will not hold or bind in pressing. This in turn is placed in the
frame and a careful press taken. The result is a sunk design into which a
different coloured clay is pressed, the tile being first allowed to
toughen. The surface is lightly scraped flat and the tile slowly dried.
When hard, the face is scraped again with a steel straight-edge,
sandpapered, and dusted, when the design appears in two colours. (Fig.
43.)

[Illustration: FIG. 42--CLAY LAYER CUT OUT ON BAT & PLASTER DIE.]

The most effective clays are fairly siliceous reds, buffs, browns, and
greys. When tempered with flint or quartz sand to a uniform degree, they
offer a splendid opportunity for counterchange pattern. If a soft clay
that contracts considerably is inlaid in a refractory clay, cracks will
appear round the edges of the inlay. Thus it is found best to have the
body of the tile made of the clay that contracts most.

[Illustration: FIG. 43--STRIKING OFF FACE OF TILE IN FRAME--SECTION ON
A-B.]

Where only a single tile is required a more direct method is possible. The
tile is pressed and allowed to toughen slightly, the design being
transferred as before. It is then cut round with a sharp knife and the
waste removed with a wire tool. A certain facility of handling is
required, for great care must be taken to preserve the edges and angles.
This method is, however, productive of much fresh and vigorous work.

Encaustic tiles must necessarily be simple and bold in character, for
anything complicated invites confusion; the best possible guides are the
encaustic tiles of mediæval times, especially the simple and spirited
English and German Gothic.

The most satisfactory way to make modelled tiles or panels is to run out
upon a stout board, cross battened to prevent warping, a flat slab of clay
of the required thickness. Sketch in the design with a point and model
straight away onto the clay. Care must be taken, if the panel is to be
fired, to see that all the added work adheres firmly to the background.
Where several presses are to be made, the edges of the modelled slab
should be carefully trimmed with a bevel, the board oiled, and the mould
made directly after the modelling is finished. The mould may be worked on
in moderation. Lettering is much more easily incised in the mould than
raised in the clay. For tiles needing much sharpness of detail almost the
whole can be carved in the plaster. Unless done with great sympathy,
however, this leads to a certain harshness and angularity that should be
foreign to clay. Where a moulded frame for a panel is required, a
_strickle_, or profile, is cut in zinc. For short use one made from a thin
slab of plaster will serve. The strickle is keyed to a straight-edge and
dragged over the clay until the correct moulding emerges. This is then cut
into lengths and very carefully dried.

The tendency of all transparent glassy glazes to pool in hollows and run
off at high points must be borne in mind. With thick matt glazes any
delicacy of detail is apt to be lost labour. These problems should be
faced before the design is made, as in this process there is a certain
quality of surface required by the glaze. On the other hand, in
endeavouring to make a good surface for the glaze to enhance, it is easy
to slip into the over-round and slimy treatment that characterizes so much
modelled pottery.



                               CHAPTER IX

                           DRYING: FINISHING

      “There nis no workeman whosoever he be
      That can werke bothe welle and hastile.”

                                       --“Merchants Tale.”


Drying out is quite an important part of pot making. For this a drying
cupboard is a necessity. It is easily erected, if the front and sides of
wood be backed against a wall. Across the bottom, which should be open,
run a row of gas jets protected above by perforated zinc or iron. At the
top, which is boarded in, place a small sliding panel to insure a draught.
With side brackets and removable shelves it should answer all purposes. A
cupboard may be built over a radiator, but here the heat is not so easily
regulated.

A thermometer inside the cupboard will be an advantage, for a wet pot
straight from the wheel will warp in a warmth that would be quite suited
to tough shapes. The green or damp wares should be put on the top shelves
and brought nearer the heat as they dry. Large shapes put into the
cupboard to dry quickly are very liable to crack across the base. Any
flush of heat upon them through any aperture in the shelves will cause
them to dry streakily. Turning then becomes difficult or impossible.

Bowls, if not too fragile, may with care be piled one within the other.
This helps to retain their shape. Tiles are best stacked in piles dusted
with flint or with a piece of clay at each corner between them. Tiles
should never be placed in the cupboard until quite dry and straight. Flat
platters or dishes require very careful drying to prevent buckling and
should be reversed on a piece of sanded glass. When shapes are dried in
the open air, they often get hard at the rim before the bottom stiffens.
They need reversing to counteract this tendency.

To retard drying, which may often be necessary, a damp-box is needed. A
large box, zinc-lined and fitted with plaster slabs, is an excellent
device. The plaster must be kept moist with water. A well-tarred box with
a close-fitting lid is more easily constructed and will serve most
purposes. All work to be _stuck up_ or modelled on should be kept in the
damp-box until quite finished and then dried very gradually.

In all kinds of sticking up the body and the addition should be of the
same consistency. Re-wetting is dangerous but may be resorted to in
moderation with stout thrown shapes. Ornament added when the shape is
nearly dry is very likely to leave in the biscuiting, although apparently
quite firm in the green state. Cast shapes dry very rapidly and should be
finished before they become white dry. With practice handles, masks, and
the like can be affixed in the dry state with slip, but it demands its
careful and sparing use. Cracks or holes in dried shapes can with great
care be filled, a stiff wedge of clay being firmly pressed in and welded
to the slightly moistened sides of the crack. The plaster tools (Fig. 44)
will be found very handy for working on the dry clay. With skill and
patience much repairing may be done on unfired shapes, but it is a waste
of time to attempt it unless the beauty of the piece warrants it. It is
far better if the piece be faulty to throw it back into the bin at this
stage. Once fired, it is likely to remain an irremediable eyesore.

[Illustration: FIG. 44--PLASTER TOOLS.]

One or two other points bearing on finish have been mentioned before in
previous chapters, but these last touches are so important that they will
bear some reiteration.

The finality burned in by the biscuiting should induce a careful and
sound completion of each object; yet paradoxical as it may seem, the less
finishing, the better for the piece. It is no part of a craftsman’s work
to go finnicking with file and sandpaper; too frequently nothing remains
of what might have been a vigorous shape but a meticulous finish. The best
Japanese work was superb in this respect and despite the many quaint and
surprising shapes into which they fashioned the clay, it very rarely seems
to lose its plastic character, it never assumes forms more suited to
metal, wood, or stone. Again the character that comes with correct
treatment is never smothered. Often the ribs or ridges made by the fingers
or the tool in forming the shape are frankly left to contribute their
quota to the general effect. The lips are rounded with scrupulous care and
angles removed without a suggestion of weakness.

Where large utensils, ewers and the like, are in question, mediæval
pottery is rich in suggestion for handles, spouts, and such added forms.
It is only when such additions are affixed that one realizes the nicety of
adjustment required between the size, shape, and situation of the handle
or spout and the vessel to which it is attached. It is here that an
appreciation and an intelligent use of historic ornament is necessary.



                               CHAPTER X

                             FIRING BISCUIT

  “The Pope, the Cardinals, and the Princes of the World are
    astonished that such excellent and noble works can be made out
    of the earth.”

                            --EXIMENUS. Fifteenth century.


When sufficient green shapes have been accumulated and are white dry, the
next stage will be _biscuiting_. This process is the firing of the clay to
a primrose or a white heat according to its fusibility. This permanently
expels the water that is always present, even when dry, and converts the
friable clay into a hard unalterable body. This may vary in colour from
the white of kaolin to ivory, grey, buff, red, or brown, according to the
composition of the clay; it may be vitreous or porous; soft like common
flower pots or so hard that it will spark when struck with steel.

The fire is the ultimate test of the pot and of the potter. It is
indispensable to both. With but a small kiln the craftsman will begin to
appreciate many things that can be learned only at the _fire hole_.
Without a kiln he will not commence to be a potter.

[Illustration: FIG. 45--GAS KILN. SECTION SHOWING CLOSE PACKED BISCUIT.]

The kinds of kilns usually found in schools are the gas and the oil kiln.
The English gas kiln has an arrangement of nine or twelve burners beneath
the muffle. (Fig. 45.) This is a fire-clay box, open at the front, set on
fire bricks and cased round with fire tiles within an iron frame (see
cut). There is an air space all round, except at the open end, leading to
the flues on top which have dampers to regulate the draught. The open end
may be closed by a hinged door or bricked up with fire tiles cut to fit.
The defects of this kind of kiln are too sudden access of flame to the
bottom of the muffle, causing it to split, and the impossibility of
getting the front, where trials are usually placed, fired up equally with
the back. An ideal muffle of this kind would be one with flues all round,
gradual access of flame on all sides, spy holes each end, and the top to
lift off, for placing. American kilns have flues in the door, and the
chimney at the top is placed slightly forward, thus making it easy to fire
the front up hard. They are usually fitted with two large burners, with
air mixers, and a handy mica spy hole.

The oil kiln differs considerably from the gas kiln. The oil is fed
through tubes into fire boxes some distance below the bottom of the
muffle. It burns on asbestos fibre in an iron pan to which the draught can
be admitted. The flames strike the bottom of the muffle and pass up
through fire-clay pipes, which project into the muffle, then pass off
through a twin flue regulated by dampers. With this kiln a long flue is
necessary and any excess of carbon is liable to choke the pipes, and
further it cannot be “sweated” up at the finish so easily as a gas kiln
having a large number of burners.

It is a good plan when a coarse fire-clay muffle is used for glaze and
biscuit to give the sides and top a sagger wash of lead and stone. This
renders the muffle less liable to absorb glaze from the pots in glost
firing. It also lessens the danger of small bits scaling off and sticking
to the finished ware. The bottom should always be kept dusted with finely
powdered flint. When cracks appear or joints open, they should be stopped
with a pugging of fire clay and grog. A mixture of egg silica or water
glass with fine grog and quartz sand will stop small cracks. _Siluma_, a
fire-proof cement, with equal parts of sand, answers admirably for
patching.

In biscuit firing the green shapes may be packed close together, with the
lighter shapes on top of the stronger, but all must be 1/2” to 3/4” away
from the sides of the muffle. Triangular pieces of biscuit, called
saddles, are used to raise the shapes off the bottom, but often a fired
tile, sanded and placed on a spur or saddles, gives the best foundation.
Where two layers are required, small props and fire bats, perforated to
let the heat through, will be necessary. These form shelves as the
exigencies of the packing dictate. (Fig. 47.)

For light shapes, thimbles and fired tiles will serve the purpose. (Fig.
48.) Where a shelf or prop rocks insecurely, a small wad of pugging (grog
and clay) will give a steady bearing. Thrown bowls, if dried together and
well fitting, may be fired together, and large thrown pots may be filled
with little ones. Cast shapes can be placed on top of thrown ones, but no
liberty is to be taken with them. Flint should be used liberally to
prevent sticking, which may happen if the biscuit be over-fired. Tiles can
be fired two together in tile boxes or stacked as dried. Flat ware fired
in a small muffle requires very careful handling. Whenever possible, it
should be placed in the centre, on a flat flint-covered fire tile or bat.

One soon learns to pack a biscuit kiln, using saddles, spurs, stilts,
thimbles, bits of tile or biscuit, and sand or flint as necessary. The
thing that is a little difficult to realize at first is that built or
thrown shapes, and still less tiles or modelled work, should not be
hurried. Twelve hours is none too long to give to a 5/8” tile in the
biscuit kiln. Although to all appearances thoroughly dry, the least hurry
generates steam which will ruthlessly blow our best effects to bits. In
packing, two cones or temperature indicators (Fig. 46) are placed
somewhere near the middle in a position easily seen during the firing from
the spy hole.

These cones are made of different compositions which melt at varying
temperatures. Thus if the firing point of a body is known, a cone of that
degree is used and the firing continued until the cone bends. This it does
soon after it assumes the colour of the surrounding muffle.

To eliminate the uncertainty that is likely to be present at the first few
firings it is as well to use two or even three cones, one just above and
one below the correct temperature. Placed in order there is little chance
then of over- or under-firing unless so much sulphur gets into the kiln
that the cones harden and refuse to turn. Calorites are sometimes used but
are not so reliable. The cones may be sloped to insure bending to right or
left, as a cone bending towards the spy is deceptive.

[Illustration: FIG. 46--CONES.]

A trial piece of biscuit being placed near the spy hole, the next thing is
to close the muffle. In a kiln with hinged doors the spy hole is fixed and
this fact has to be taken into account. But with a bricked-up door the spy
and vent may be left where it is most convenient. These orifices have
plugs that fit them loosely so that if necessary they can be pulled
without disturbing the clamming. This clamming or stopping is a mixture of
sand, sieved dust, ground pitchers, or other infusible siftings held
together with a very little waste glaze and water. Where much is required,
moist sand will suffice. This is plastered into the cracks that would
otherwise let heat out of, or air into, the muffle, and so seals up the
door. With hinged doors little stopping is required, except round the spy
or vent. The crack above the door should not be clammed until the muffle
begins to get warm. With this done and the two plugs out, all is now ready
to light up.

With an English kiln, a good middle course is as follows: For cone .01,
taking 12-14 hours. See that all the burner taps are off with the main
cock on one third to one half. Take the reading of the metre. Pull the air
regulators right back and the dampers out nearly half. Then take out the
plug of the lighting hole and insert a taper. Turn on tap number 1. When
lit, withdraw the taper and turn on tap number 2. Turn down to about one
half and continue until every burner is lit, making sure that each one is
burning freely with a yellow flame. With a kiln having twelve burners turn
out all but numbers 3, 6, and 9. With these on one third, very gently push
forward the air regulators until a roaring noise tells that air is being
admitted to the bunsen burners.

The flame at this time should be blue, and the stopper should be replaced.
If the flame appears at all fierce, turn the taps down a little. If
turned down too much, the gas lights back and will have to be turned out
and relighted. The same thing happens when too much air is admitted. The
burners require watching until the right pressure is known.

[Illustration: FIG. 47--THE USE OF BATS & PROPS.]

For biscuit of any thickness three hours on the three burners is not too
much, the taps being gradually turned on to increase the length of the
flame until at the end of the three hours the taps are at three fourths.
At the end of the first half hour the bottom spy hole is plugged and when
all steam has stopped issuing from the top vent, that is stopped also and
the whole clammed, leaving just a small crack as vent. When three hours
are up, the regulators are pulled back and all burners lit at half cock.
Then all but 2, 5, 7, 9, and 11 are turned out. Starting at the half, they
are gradually increased to three fourths in two hours. Then numbers 1,
2-4, 5-7, 8-10, 11 are lighted in the same way. Colour will begin to show
inside the muffle about the fifth or sixth hour, and the top dampers can
come out a little, the front one more than the back, to draw the flame
towards the door.

[Illustration: FIG. 48--TILE THIMBLES.]

When the eight burners have been on about one and one half hours the
muffle will probably show a dull red inside and all danger of blowing will
be passed. Two more burners at three fourths may now be put on and at the
expiration of another one and one half hours the remaining two may be
turned on. If the pressure weakens and the flame shortens, the main cock
should be turned on. Just above the base of each chimney is a small hole
and the flame should show through these towards the finish. If the flame
flaps out of the chimney tops, it is so much waste and it should be
checked at the taps. The dampers can come right out towards the end, being
used to _sweat_ the flame to the front if the back appears to come up too
fast.

As white heat approaches, the cones should be observed occasionally. They
turn the colour of their surroundings when about to topple over and as the
first begins to curl the trial near the spy can be hooked out quickly and
tested. When the right cone is well down, the main cock and then the
burner taps are turned off. The air regulators are now pulled back and
after a few minutes the dampers are closed. The metre is then checked and
entered in the firing book.

The kiln should be allowed to cool slowly for at least 12 hours, but the
clamming at the top may come away and this will expedite the cooling
without risk to the muffle. This time applies to a muffle of about 20” ×
15” × 30” dimensions. A smaller kiln will fire up and cool in a shorter
time.

Gas kilns as made in America vary in the arrangement of their burners, but
the principle is the same. They are simple to manipulate and especially
handy for firing “on” decoration, as they are fitted with shelves and
uprights. The burners once alight, the flame is gradually increased, but
where the pressure is uncertain, it is well to keep something in reserve.

Firing with oil is somewhat different. The asbestos fibre in the pans is
well saturated with kerosene, the tanks filled, and the taps turned off. A
light is applied to the burners and when both are burning freely the taps
are turned on to allow a thin stream of oil to flow into the pans. From
the merest trickle at first, the flow should be gradually increased as the
heat develops. This is observed through the mica spy hole in the door and
the one above tells when the flame is reaching its maximum. Should it
flare over irregularly before the finish it means that the combustion is
not perfect and there is danger of clogging. The supply of oil should be
reduced and the draught regulated until the flame in the combustion
chamber burns clear.

All soot or carbon forming in the fire box should be raked out and the oil
supply checked, as it indicates a too liberal supply. As the oil in the
tank subsides it should be refilled and the taps checked, as the increase
in pressure is apt to vary the flow.

The later patterns of oil kilns have several advantages over the kiln
described. The muffle construction and the burner arrangements are
ingenious and practical, and need little manipulation to insure even
distribution of heat.

The oil tanks and taps will need attention at each firing, otherwise
sediment will collect and choke the even flow of paraffin oil or kerosene.
With both gas or oil kilns the amount of fuel consumed should be recorded,
together with the time, weather conditions, cones, and results of firing,
in the “Kiln Log.”

[Illustration: FIG. 49--SKETCH SEC’^{TN} OF OIL KILN TO SHOW PACKING OF
GLAZED POTS.]



                               CHAPTER XI

                              GLOST FIRING

  “When Fortune bringeth thee affliction, console thyself by
    remembering that one day thou must see prosperity, and another
    day difficulty.”

                                          --From EL KORAN.


The hard porous biscuit shape will now need a coat of glaze and a
subsequent glost fire.

Raw glazes for green shapes are now seldom used except for the coarser
wares or peasant pottery. In commerce it is, however, largely used on
tiles, mouldings, and big sanitary appliances. For common cheap crockery a
soft lead glaze, often galena, is generally used. It is applied with a
brush, or the pot still leathery and tough is dipped in the glaze. Raw
glazes have a strong inclination to leave in the firing. They are very
difficult to manipulate unless they are of the simplest formula and fired
very slowly. The addition of a little clay in the form of slip to the
glaze will often counteract the tendency to leave the pot.

The ordinary glazes in dry powder form are mixed with water to the
consistency of cream and passed with the aid of a stout brush through a
phosphor bronze sieve into a large basin or tub. The sieves may range
from eighty to two hundred mesh, according to the delicacy of the work.
For ordinary work No. 100 suffices. The biscuit to receive the glaze
should be quite clean and free from dust or dirt with the insides
carefully dusted or blown out. Grease will stop absorption, but with
opaque glazes discoloration is not of great importance. If the biscuit is
hard and inclined to be non-porous, the glaze will need to be mixed fairly
thick before it will cling; with soft and porous shapes a comparatively
thin mixture will take readily.

No immutable law can be laid down for the exact thickness of the coat of
glaze. All glazes vary. One sixteenth inch may be enough for one and far
too thin for another. From one twentieth inch for thin transparent glaze
to one eighth inch for matts is a fair average. It is well to err on the
thick side to avoid an impoverished look. Trials on odd pieces of biscuit
fired in horizontal and vertical positions will best settle the point.

In all cases the inside is first half filled with glaze which is rolled
quickly round and out. The deposit is then tested with a knife. The glaze
for the inside should be slightly thinner in composition than for the
outside, as it is inclined to pool in the bottom if too thick. The outside
and the neck are then scraped free of all splashes.

[Illustration: FIG. 50--POURING.]

To glaze the outside of the pot the methods employed are painting,
spraying, dipping, and pouring. In painting, two or three coats applied
with a flat soft brush may be necessary. In spraying, the glaze is thinned
considerably and blown through a vaporizer by means of a foot pump. (Fig.
51.) The shape, its mouth closed with a small bowl or saucer, is placed on
a whirler in a draught box and slowly revolved. The draught draws the
waste spray away from the operator, who should wear a respirator. This
method is excellent where any gradation is required. It is easily learned.
Unfortunately, it requires expensive apparatus to render it safe with lead
glazes. Unless it is done on a big scale and the waste glaze retained, it
is also wasteful.

In dipping, the pot is plunged right under in a tub of glaze which is kept
well stirred to prevent the heavy constituents settling. (Figs. 52 and
53.) This requires considerable dexterity. In a school, glaze is seldom
mixed in sufficient quantities to permit of this being acquired.

Perhaps the most satisfactory method is pouring. (Fig. 50.) The shape is
reversed and stood upon a big stilt or two strips of wood over a bowl or
tub. Then the glaze is poured from a jug round the edge of the base, until
every part is covered. With a little practice a quite even coat can be
thus applied. Owing to the inversion of the shape it is slightly thicker
at the shoulder and neck, an excellent point in glazing. When dry, the
base is scraped and wiped clean with a sponge and the lip touched up with
a brush.

[Illustration: FIG. 51--SPRAYING.]

With matt glazes, as has been noted, a thick coat is necessary. If very
porous, the shape may be soaked first in clean water to take some of the
suction out of the biscuit. When glazed, it is essential that all dips and
inequalities be removed. If thinly coated, the glaze will assume a glossy
surface when fired.

[Illustration: FIG. 52--DIPPING.]

Whatever process is used, the lip and base of a pot should receive careful
attention, the rims especially should be thickly and evenly coated with
glaze. The thickness can be tested with the point of a knife and any
scratches or bare spots should be filled in and rubbed flat as they are
apt to show at the finish if the glaze is at all refractory. Never starve
the glaze, for a thin coat imparts a poor cheap look to any pot that is
seldom remedied with entire success.

When only one kind of glaze is used, the application is quickly learned.
With hard and soft, lead and leadless glazes, both opaque and transparent,
and possibly a combination of spraying, painting, and pouring, the
difficulties are greatly increased. Practical experience will be the only
safe guide. But speaking generally, a sprayed coat can be thicker than a
poured coat. Hard glazes give less trouble than soft if too liberally
applied. Tin glazes will stand a lot of over-firing even when thin and the
reverse holds good of matt glazes. Raw borax glazes require much more
careful firing than raw lead glazes but often give better colour results
and are less liable to sulphuring.

[Illustration: FIG. 53--DIPPING.]

When glazing with a transparent glaze over under-glaze painting a thin
coat is advisable. If it be thick and run, the painting is spoiled; but
if, after firing, it appears thin, another light spray may be tried. But
whole chapters of writing will never settle these points. Repeated trials
on odd pieces of biscuit will elucidate more than many books. In packing a
glost or glaze kiln stilts and spurs instead of saddles must be used to
prevent the pots from sticking to the floor or shelves. (Figs. 49 and 54.)
For the same reason the pots must not touch each other. With glazes
requiring a high temperature the space between pots of different colour
should be considerable. An appreciable amount of glaze is liberated in the
intense heat and a blue pot will often leave a distinct blue patch on any
light pot placed too near. Soft glazes liable to run or drip should be
placed on separate bats well flinted beneath. Any crack in the muffle
should be well stopped and lime may be used to neutralize the effects of
any sulphur that may enter.

[Illustration: FIG. 54--STILTS, BITS AND SPURS.]

As the back is usually hotter than the front the hard glazes should be
packed first, and by selecting suitable shapes a good _setter_ will pack a
surprising amount into even a small kiln. The clamming should be done with
care, as bits are liable to flake off and stick to the glaze. The top plug
only need be left out and the lighting up proceeded with as before.

The gradual increase of heat is very essential in firing glaze, for any
sudden jump or reduction will play all manner of games in a glost oven.
The slow start is not so important, there being no risk of _blowing_.
Indeed the glaze is best in a sharp quick fire.

Although cones should always be used and are excellent indicators,
experience will soon show when a kiln is fired up. It may be advisable to
go on a little after the cone is over until all looks fluxed so as to get
rid of bubbles. These appear in some glazes until the last. They do not
always go down on cooling, but those glazes that bubble through
over-firing should be avoided. Possibly the trouble will arise from
sulphur in the body which must be corrected. Trials are always useful but
they must be small and easily hooked out, as constant poking about at the
spy hole lowers the temperature of the muffle at the front, just where it
is most difficult to get it up.

When fired, a glost kiln should cool very slowly, for any sudden access of
cold air is liable to stunt or crack the pots. When firing over glaze
decoration where the glaze does not run, the packing is much simplified.
With low-firing lustres the pots may even touch each other.

All this has been set out at great length but we shall find over and above
this that each kiln has its own little ways which must be studied and
humoured before the best results can be obtained.

The chief thing to avoid is a sudden flush or jump in the heat. The main
thing to aim at is a slow start steadily increasing to a sharp finish. The
state of the muffle, a dry or a damp day, will modify each firing a
little, but the above generalization will have a fairly wide application
to the working of a small kiln.

Unpacking is a compound of despair and delight, and is best done slowly.
As the colour dies the clamming, if any, may be knocked away, and later on
the spy plugs removed. When comparatively cold, the door may be opened
slightly, and left so for one or two hours. Then the front pots can be
extracted but those at the back should be allowed another half hour. Be
very careful of the razor edges of broken stilts or glaze dips. A steel
chisel should be used for chopping rough edges or removing refractory
stilts. If necessary the bases may be ground on an emery wheel until the
pot stands true.



                              CHAPTER XII

                           GLAZES AND LUSTRES

  “I began to think that if I should discover how to make enamels I
    could make earthen vessels and other things very prettily,
    because God had gifted me with some knowledge of drawing.”

                                                --PALISSY.


It is in this department of potting, with its surprises, difficulties, and
disappointments, its rare but exciting successes, that for most potters
the greatest interest lies. To those of a scientific bent it is perhaps
the summit of the craft, but the artist groping amidst formulas and
methods may take heart. The finest work in pottery was not produced by
scientists alone and does not depend altogether upon the quality of its
paste, its unique colour, or strange lustre. The last word, the form,
decoration, and craftsmanship, is with the artist.

It is beyond the scope of a book of this description to enter into a
necessarily long and complicated account of the different processes
concerned in the composition of glazes. It will be sufficient to indicate
their leading characteristics plainly enough to enable the student to
start experimenting. None can afford to miss opportunities for
experiment, just as surely as none can afford to be always experimenting.
For a full description of materials and glazes and their manufacture such
books as those of Drs. Shaw, Furnival, and Hainbach are recommended.

Putting aside salt glaze we find a countless number of both lead and
leadless glazes. They range from the thin silicious coating of the
ancients up to the rich alkaline glazes of the Persians and Chinese; from
the raw galena of peasant pottery to the rich Majolicas and fine hard
glazes of modern commerce. Salt glaze is obtained by the vaporizing of
salt inside the kiln at a great heat. The sodium oxide so formed combines
with the silicates in the clay to form a very thin coat of refractory
glass, intimately connected with the body. Porcelain glazes, though not
differing so much in composition from the ordinary _fine_ earthenware
glazes, are extremely hard, being compounded of kaolin, felspar, and
quartz, with possibly limestone and ground sherds. It has in common with
the salt glaze the close union with the body, so that when fractured the
line of demarcation between glaze and body is indeterminable.

With a few minor exceptions the following list comprises the ingredients
of all colourless glazes:

  Kaolin
  Quartz
  Cornish stone
  Felspar
  Fluorspar
  Flint
  Sand
  Barytes
  Bismuth
  Gypsum
  Limestone
  Nitre
  Borax
  Bone-ash
  White lead
  Red lead
  Zinc oxide
  Tin oxide
  Salt
  Soda
  Potash

These materials must be free from all trace of iron. They are pulverized
and some are calcined or oxidized. Then they are mixed in varying
quantities to form the glaze mass. This mass is easily fusible when lead
or borax is present in large proportions, more infusible or harder the
more silica it contains, and very refractory if alumina is present in any
quantity. The silica forming the glassy part of the glaze is stiffened by
the presence of alumina, which stops any tendency to run.

Lead is very largely used as a powerful flux at low temperatures but is
unsuited to hard glazes. Borax and boracic acid are important constituents
of leadless glazes. They are used to replace some of the silica, than
which they are more fusible. Matt or non-reflective glazes are opaque and
less vitreous than the glassy glazes. They do not flux or run.

All these minerals are finely ground before mixing. Then those insoluble
are mixed and _fritted_; that is, fused in a crucible or fritting furnace
to a greater or less degree, according to the hardness of the glaze. If
fused into a glass, the melted mass is poured into water to facilitate the
next process, which is its reduction to a fine powder by re-grinding. Then
the completing ingredients are added and the mass coloured by the addition
of metallic oxides. Of these the chief are:

  Iron
  Copper
  Nickel
  Antimony
  Cobalt
  Chrome
  Manganese
  Titanium

and the more precious metals, in various forms, as oxides, carbonates,
sulphates, and nitrates soluble in the glaze at great heat.

These metals impart the many varied colours found in pottery. Zinc oxide
is used to brighten a glaze or to stabilize colour. Tin oxide, which is
insoluble at great heat but remains in suspension, gives opacity.

This is no more than a skeleton outline of the intricate processes often
used in the fabrication of a glaze. The manifold minerals, metals, oxides,
acids, and alkalies are used in a variety of ways by the modern chemical
potter.

To all this seeming complication is added the question of pastes and
bodies. There then arises the great problem of fitting one to the other.
Salt glaze and porcelain excepted, the finished pot presents three
stratas. Outside is the glaze, next the body, then inside the glaze again.
If the coefficient of expansion of these three layers differs, in other
words, if the glaze does not fit, the result is _crazing_, that bugbear of
the potter.

This crazing, which has been followed up and developed into their
delightful _crackle_ by the Chinese, may show itself at once or only after
a lapse of months. It appears as a minute network of fine cracks over the
entire surface of the pot. It is often not unsightly, but sooner or later
it must cause devitrification. The glaze after a time assumes an
evanescent iridescence followed by a dull smoky appearance; finally,
perhaps not for many years, it decomposes and peels off.

With low-firing natural clays rich in silica and iron, the craze is not of
much consequence. The body itself at a moderately high temperature becomes
non-porous. With hard short bodies containing lime or chalk it may have
quite disastrous consequences. Water placed inside will eventually
percolate through leaving a network of grey lines all over the pot and
completely spoiling its appearance.

It will be readily granted that, whether porous or non-porous, a craze is
most undesirable on any piece of pottery that may be used for food or
drink.

It is here that the commercial potter is such an admirable fellow. Many of
the glazes on modern tablewares are perfect for their purposes. Sometimes
only a little more fire is needed to stop the nuisance, but a bad craze
usually needs more attention. The glaze requires stiffening, and the
addition of ground flint or quartz, China stone or clay and felspar
introduces alumina and silica and raises the fusing point. The
substitution of borax for a portion of the silica can also be tried and
will permit the use of slightly lower firing point.

If the glazes are bought ready mixed, the body must be altered instead.
Refractory China clays should be replaced by more fusible clays or some
reduction made in the amount of infusible materials. The addition of
ground sherds or flint will have a contrary effect should the glaze peel
or crack at the edges, as it may do on a very silicious body. In working
with natural clays on a moderate scale it will be found best to mix “fat”
or rich natural clays with those of a more porous or hard nature. A few
graded mixtures submitted to a thorough trial should soon show when a
sympathy has been established between the body and glaze.

The receipts given on pages 183 and 184 will make good colourless glazes
without fritting if thoroughly ground in a mortar and passed through a
sieve. Numbers 3 and 7, when calcined, will give much more even results
and they can be coloured by the addition of the oxides named. But simple
as it sounds, the washing, grinding, fritting, re-grinding, and sieving is
a long and laborious process demanding machinery, and on that account is
unsuited to schools or potters of moderate means. Glazes like Nos. 1 and
2 will do quite well for elementary work but unless the appliances are to
hand the manufactured article will have to be relied on for more finished
and ambitious work.

If, indeed, you are already in possession of a good receipt for a fine
colour and glaze, one quite worth while, so much the better. Mix it and
feel the joy of the Compleat Potter unafraid of spoiling his own good
shapes with a faulty or unknown glaze.

Admittedly, to get anywhere in an original direction systematic research
is essential. One must keep on experimenting, keep on hoping, and keep on
taking notes; but at the start let us not be too impatient or independent
if we wish to produce good pots.

There is often among young potters a false pride that prevents them using,
and among old potters acknowledging the use of, the manufactured article.
Why this should be is a little difficult to understand. A painter might
far more reasonably be ashamed to use modern tube colours or a
stained-glass craftsman as logically insist on making his own glass, as a
potter in the twentieth century refuse to avail himself of the wonderful
range of glazes that modern research has placed at his disposal. These
resources should be used intelligently, not mechanically, or by the
book--artistically, inventively, secretly, if you will, but they should be
used--until the multitudinous experiments have borne fruit and repeated
trials convince you that at last you possess some gem of research worth,
as well it may be, the months of patient toil engendered in its
production.

The various receipts are given on pages 183 and 184 without analysis of
the composition of the paste or body to which they were applied. The first
group have been used on common earthenware clays with complete
satisfaction. They are to be considered as points of departure for future
experiments in which they may be modified at will, and not regarded as a
contribution to the science of glaze making.

In colouring it will be found that combinations of cobalt, iron, and
copper oxides give an interesting range of simple blues or greens; iron
and manganese browns; and so forth. The colour mass or stain is ground
fine and lawned, and from about 2 to 7 per cent mixed with the colourless
glaze mass, according to the depth of colour required. The ordinary
under-glaze colours may be used to stain glazes, the percentage being
fixed by small trials. For the rare colours--turquoise, crimson, or
purple--a more complicated process is necessary and only perfected after
many trials. The ingredients of these fine colours are naturally kept
secret by their fortunate possessors.

It must be noted that a glaze suited to one body may peel or run off an
unsuitable one. Then a colourant is affected differently by a lead or an
alkaline base in the glaze. Again, copper and iron oxides may help to flux
a glaze, whilst cobalt or nickel will exert a contrary effect. Cobalt,
being a strong colourant, will need a sparing use, whereas a similar
percentage of iron will merely tinge the glaze mass. And so _ad
infinitum_.

It is self-evident that any attempt to emulate the vast range of the
modern ceramic chemist is doomed to failure. To a craftsman the
fabrication of one fine individual glaze or lustre is an achievement of
which he may be proud, and for which he will find abundant and varied
uses. In this connection it is encouraging to the craftsman to learn from
so high an authority as W. Burton, Esq., F.C.S., that it is impossible to
obtain with purified oxides the fine tones got by the Orientals with
impure materials. Further, that the simple glaze of the Persians--a
mixture of clean white sand with soda or wood ash or potash--is still the
best for under-glaze painting. Although tastes differ so widely,
invariably it will be found that more and more heat will be the cry.
Imperceptibly this leads to the desire for hard, cold, “fat” translucent
glazes, neither matt nor glossy. And on the summit, far out of reach,
stand the wonders of the Old Chinese.


                                LUSTRES

There are several kinds of lustres, but the true lustres possess a pearly
iridescence in addition to their colour. The copper and silver _lustres_
of the eighteenth-century Staffordshire potters were thin metallic films
over the whole surface of the glaze. Gold or silver solutions were used.
Only where the gold was fired on a white clay is there any iridescence,
and then hardly so pronounced as to deserve the name of lustre. The
bismuth and other lustres made by the modern potter are combinations of
metallic oxides and resinates dissolved in ethereal oils. These are
painted on the glaze, transparent or opaque, but having almost invariably
a lead base, and then fired at a dull-red heat. The medium disappears, and
the metal in a finely divided state is deposited on the surface of the
glaze. This, however, gives a painted look very different from the lovely
irradiance of the Persian Hispano-Mooresque or Italian work.

With these the lustres were fired in a reducing atmosphere, one
supercharged with combustible gases, the metals decomposed and fixed to
the semifluxed glaze. The manipulation was not infallible and was attended
with much risk; but the successful pieces are unrivalled, and according to
Piccolpasso “paid in gold.” De Morgan, who more nearly approached the
works of the Italian masters than any other modern potter, used a very
similar medium and method with his fine lustres. In the last few years
lustres have been brought to such perfection, in preparation, application,
and firing, that accident is practically eliminated. Glorious colours and
gorgeous effects are obtained. Yet it may be said without senseless
adulation of the merely mediæval that nothing has been produced superior,
or even akin in spirit, to the work sent out from Persia, Spain, or the
botega of the inimitable Maestro Georgio of Gubbio.

Lustres may be bought ready to apply. They are then painted on the glazed
pot, which is re-fired at a dull-red heat in the ordinary oxidizing
atmosphere. Once the painted look has been contrasted with the lustrous
appearance of the _reduced_ effects there is only one kind of lustre for
the artist. Fortunately, perhaps, their preparation is not easy, and the
correct method of reducing is a difficulty to be overcome by practical
experiment alone. Hainbach gives many practical receipts for lustres that
are not beyond the scope of a craftsman. The reducing atmosphere can be
obtained in an open kiln by the introduction at the right moment of any
combustible giving smoke free from all traces of sulphur.

In firing with a muffle kiln the introduction of coal-gas free from
sulphur is a matter attended with some risk at the necessarily low
temperatures required by the lustres. It should be approached with
caution, and each mixture will have a varied firing point, the correctness
of which is established only by trials.

Lustres applied with skill and restraint enhance the most beautiful glaze,
but in unskilled hands they inevitably vulgarize and cheapen. The fresh,
unsophisticated renderings of the Persians or the Moors and the virility
of the Italians should be studied, but not merely imitated before working
in this medium.

[Illustration: FIG. 55--PAINTING OUTFIT.]



                              CHAPTER XIII

                               DECORATION

              “The world is still deceiv’d with ornament.”

                                   --_Merchant of Venice._


Decoration has been touched upon briefly in one or two of the preceding
chapters. To attempt a description of the various kinds of decoration
which it is possible to place on a pot, another book would be needed.
Their name is legion. They range from the simple and entirely satisfactory
work of primitive and peasant peoples to the wonderful enamel decorations
of the Chinese. With such an enormous field and varied choice it is
difficult to particularize and foolish to dogmatize. The hints below are
intended but to stimulate interest in the at present unexplored fields
that lie beyond the beaten track.

Any representative collection of ceramics will prove a veritable treasure
house of suggestion to the student. All will be there. The difficulty is
to choose, and choose aright. The bold brushwork of Cyprus foils the
marvellous _familles_ vert and rose of the Chinese, the faultless Wedgwood
sets off the virile Toft. One sees how the Italians, with almost crude
colours,--blue, green, red, yellow,--developed their wonderfully robust
school of figure painters; then their fanciful _arabesques_ are prolific
of ideas. The Greek style--red and black and white--is a rich field
waiting for the reaper. The peerless Persian pots, the plaques from Spain,
the steins and stoves from Germany, the fresh Delft wares; these and many
others crowd round for recognition and disconcert the choice.

But having come so far, let us not choose the horrific style that models
most faithfully a cabbage, tops it with a lifelike snail as handle, and
cunningly converts the whole into a vegetable dish!... (in S. K. M.).
Nothing should be more distressing to the artist than to see great skill
and craft thus misapplied. Yet how often does the search after false
originality lead only to meretricious cleverness or vulgarity, which
creeps in unseen during the too close struggle with the craft.

But our muttons need tending. Broadly speaking, all decoration falls under
three heads: Glaze; Relief; Painting;--subdivided into many combinations
of these three classes.

The application of glaze has already been described. A pot possessing a
noble form and glaze is obviously in no need of _decoration_; no artist
would attempt it. The Chinese and Japanese are safe guides here. Their
rich glazes and fine forms are set off in the simplest and most effective
manner. This is potting, pure and simple.

Under relief, we group all modelling,--raised or sunk, embossments,
flutings, mouldings, feet, handles, or applied figures. At one extreme
come the earliest attempts at decoration in slip or clay, highly developed
in the Gallo- and Egypto-Roman and Romano-British wares. The matured slip
must be applied fairly thick to the still moist pot and then dried slowly.
Any work applied to dry shapes is liable to crack in drying or leave in
firing. Probably the most effective use of slip is seen in the old tygs
and dishes of Toft and others of his time.

The simple spotting and surfacing has been carried to perfection by the
Martin Brothers, who have drawn largely upon the vegetable world for their
inspiration. Roman Aretine ware shows finely executed reliefs of foliage
and figures. The enrichment was probably worked on the original shape, a
mould was then taken, and the vessel pressed. (See chapter on Casting.)

Wedgwood carried this method still further (too far, maybe) and used
different coloured bodies. The reliefs, so finely modelled by Flaxman,
were fired, and from them moulds of a very refractory clay were made,
called _pitcher moulds_. The reliefs were then pressed and affixed to the
vase, and the whole touched up by a skilled craftsman. A naïve and
unpretentious form of this decoration is seen in the stoneware and
salt-glazed pottery of the eighteenth-century English potters and the
jolly _Bellarmines_ of earlier times. Small dies were used in the Orion
ware, the pattern being stamped into the clay. German stoneware and the
_Grés of Flanders_ show sunk and relief patterns. Between the two extremes
lies a rare choice of style.

This method of using patterns lends itself particularly to fine commercial
work when used with the restraint seen in the best of the above-mentioned
styles. To the craftsman it offers a welcome chance to enlarge his
production, but he must be well equipped. It is easy to acquire the mere
mechanism of commerce without its splendid technique. Finally, the further
the relief is developed the less will be the appeal of form and the less
the possibilities of glaze.

The next division is painting.

It is in this branch of ceramic decoration that the widest choice lies.
The scale ascends from the simple earthy colourants applied to the
unglazed pot in the manner of the American Indian up to the splendid
enamels of China and the sumptuous but sterile wonders of--shall we
say--Sèvres or Worcester. Much of the modern eighteenth- and
nineteenth-century work is such a technical _tour de force_ that one
hesitates to criticise it. But careful scrutiny will often show that the
artistic difficulties have been undermined rather than overcome. Thus the
frank frontal attack of the Persians on their absorbent ground or of the
potters of Delft on their unfired tin glaze is never attempted, and
probably never can be attempted in the factory of to-day.

The modern method of painting in fat oils on a prepared ground induces in
any but the most accomplished a cramped and finnicky style. The best and
really most beautiful results are seen in the delicate _vertu_ of the
eighteenth century. Snuff boxes and ladies’ knick-knacks exhibit the
loveliest miniatures in an impressible medium. How far it is desirable to
decorate pots with such pictures depends on the sophistry of the
craftsman. (For, ever since painters were pampered by princes each
erstwhile honest craftsman must needs try to turn painter!)

The Chinese who laboured with infinite patience upon their pots still
seemed to preserve a spirit lacking in the works of their western
imitators, and their avoidance of realism saved them from the many
pitfalls that yawned for the Occidental.

The manner in which the Persians and Dutch preserved their freshness has
been noticed already, but the encountering and surmounting of similar
difficulties is at the bottom of most successes. A few of the methods of
painting pots are here set forth, with some odd variants.

The colourants described under Glazes are also used for painting. Very
finely ground and prepared, they are mixed with a flux or other vehicle
and applied in various ways under or over the glaze. Simple colours can be
made from the metallic oxides. They should be finely ground in a mortar
well mixed with a little of the glaze with which they are to be used. This
will do for the simplest work. For more subtle colours rather involved
processes are necessary. The range of manufactured colours, both over- and
under-glaze, is wide enough to suit all tastes, and when working on a
small scale are infinitely to be preferred on the score of economy and
dependability.

A method of painting entirely suited to beginners is as follows: A simple
_palette_ is prepared with the colours ground upon a slab of glass. The
medium employed is a solution of gum arabic and water, the colours being
applied directly to the green shape with a brush. The difficulty of firing
glaze on the raw clay deters any attempt at high finish, and the
absorbent ground develops a desirable freedom and directness of touch.
When painted, the pot is dipped or poured in a transparent glaze and
fired. The gum prevents the colour shifting during the immersion, but does
not prevent the glaze adhering. This method can be satisfactorily employed
on biscuit. More finish can be obtained and a richer glaze used without
risk. Much skill and practice will be required to produce good stuff, as
each touch, although not apparent before, will stand out distinctly and
often disagreeably after the fire. The gum must be used sparingly; any
excess will cause peeling and prevent the adhesion of the glaze.

For a still higher finish the biscuit is sized with a solution of gum
tragacanth. This is smoothly applied until the pot is non-absorbent. The
design, if elaborate, should be drawn upon the pot with a fine graphite
pencil or, better still, India ink and brush. A common pencil is likely to
show after firing, but the ink disappears entirely. The colours are then
well ground and laid in with fat oil of turpentine or lavender oil.

To prepare the first oil, half fill a cup with pure turps, stand it in a
saucer, and spill a little over the sides of the cup. After standing a
little the fat oil is deposited in the saucer and the clear turps left in
the cup. Long, flexible brushes holding plenty of colour are used and the
fat oil thinned if necessary with clear turps. The colour should flow
easily from the brush, being neither _tacky_ nor too fluid, and constant
retouching is to be avoided. Keep all free from dust. Heavy,
greasy-looking masses should be scraped off and repainted, otherwise they
will flake off.

When the painting is finished, the colour is _hardened on_; that is, the
gum and medium are fired off in the kiln, a dull-red heat being
sufficient. This does anything but harden on, however, and the pot must be
handled very carefully or the colour will rub off. The glaze should now be
gently sprayed on, and then the final fire is given.

Another way is to apply a very thin spray of glaze before hardening on,
just sufficient to fix the colour. The pot may then be dipped or poured
without risk. In each case the oily medium must be quite dry before the
hardening on takes place. After the glost fire the decoration is fixed and
unalterable. Where possible, a hard transparent glaze is best for fine
work. A soft glaze will always run if slightly over-fired, and the result
is the obliteration of all brushwork.

Over-glaze decoration is applied in a very similar manner. Turpentine, fat
oil, and lavender oil are used: the turps to run the colour, the fat oil
to stiffen, and the oil of lavender to retard the drying. The colour must
be applied evenly and thinly, thick patches being likely to peel or crack.
On hard glazes this process lends itself to elaborate effects. The hard
and fast colours, the blues and greens, may be fired first, the delicate
pinks and greys last. The whole effect may then be enriched with
low-firing lustres. These, when bought in bottles, are ready to use and
are applied directly with a fine brush, then fired at a dull-red heat. The
pot should then be quite finished; quite frequently it is.

_Pâte sur pâte_ or painting in relief colours is another process that has
many attractive features. The colours have a clay carrier and are applied
with a gum medium. Painted boldly with a certain amount of relief, this
gives a rich enamel effect very suitable to simple figure decoration.

The full equipment of the painter will be as follows:

  Colours, under- or over-glaze.
  Brushes, tracers, and shaders.
  A stick frame for holding the vase.
  Turpentine and lavender oil.
  A slab of ground glass.
  A muller for grinding.
  India ink and a colour slab.
  A palette knife of horn for very delicate colours.
  Some soft rags.

Before risking decent shapes in the fire, trials,--on biscuit for
under-glaze, on glaze for over-glaze,--should be made repeatedly.
Graduated strips and stripes tartan fashion are the most useful and easily
tabulated. To lay perfectly flat grounds some skill and practice are
necessary. One method is to paint in the ornament or rather the space it
will cover with thick molasses or black treacle. This is allowed to harden
and the background colour applied with a soft dabber. It must be ground
fine with fat oil and applied very evenly. Then the tile or vase is soaked
in water, which causes the treacle to peel off. The oil is allowed to dry
and the piece fired. This fixes the background, and the decoration itself
is next applied.

Pierced work if skilfully done is most attractive. The pattern may be
incised on the “original,” which is moulded, the design then showing in
relief. This again shows as a slightly engraved pattern on each cast form
or shape. Then with the aid of a fine-pointed knife or plaster tool the
pattern is cut out and the edges are softened to take away any metallic
look. The Chinese and Persians are said to have used rice seeds in some of
their translucent effects. The seeds were embedded in the moist clay to
form a delicate tracery. When fired, the grains disappeared, leaving holes
which were completely filled with glaze.

The decorative possibilities of simple incised lines and plain slip
additions have been hinted at already. The slip may be coloured red or
brown with iron and manganese oxides or applied white to a coloured body.
Sharply incised lines may be filled in with colour stiffened by the
addition of a little _hard_ clear glaze or China clay. Patterns may be dug
out or stamped in and filled up with different coloured clays and the
whole glazed with a coloured transparent glaze. Scraffito work is
effective and not difficult. The green pot, tile, or dish is sprayed
evenly with a different coloured slip, usually red on white. The piece
should not be quite dry and the coefficient of expansion between the two
clays as near alike as possible. The decoration is then sketched in and
the background or the ornament itself gently scratched away to show the
ground beneath. It is then fired, glazed, and fired again. All these
processes have their uses and abuses, but they do not lend themselves
readily to elaboration or realism.

[Illustration: FIG. 56--STATUETTE FOR A THREE-PIECE MOULD.]



                              CHAPTER XIV

                               FIGURINES

  “But if you carve in the marble what will break with a touch, or
    mould in the metal what a stain of rust or verdigris will spoil,
    it is your fault not mine.”

                                                 --RUSKIN.


The making of small figures is an important department of ceramics
scarcely mentioned so far. It is one offering exceptional opportunities to
the advanced craftsman. In this branch of potting, even more than any
other, the possibilities and limitations of the clay and glaze need close
study if best results are to be obtained. The archaic Sung and Tang
figures and the well-known Tanagras are far better guides to the beginner
than the wonderful Dresden porcelain or the _bisque_ groups of Sèvres. The
Chinese and Japanese in their glazed figures show remarkable appreciation
and utilization of the plastic and liquid qualities of their medium.
Splendid and sound work, too, has been turned out in recent years in
Germany and Austria, whilst the Copenhagen porcelain is world famous.

To start with, the simplest decorative figures might be attempted. Many of
the little deities of ancient Egypt offer rich suggestions for two- or
three-piece moulds. Japanese Netsuke and Scandinavian bone carvings are
other stimulating, if more remote, fields. Next, a more ambitious but
still uncomplicated figure could be moulded directly from the clay. As the
difficulties of moulding increase, the original clay may be first fired or
a good plaster cast made. In firing the figure a very slow fire must be
used, and the modelling must be done carefully, as free from holes as may
be, and without an armature. Air holes are apt to blow, and additions of
soft clay to the model when hard are likely to crack off in firing.

[Illustration: FIG. 57--SIDE VIEW, FIGURINE.]

With a plaster _original_ some retouching is possible before the final
piece-mould is made. When modelling the head and face, the modifying
effects of the glaze used must be realized, so that such detail as may be
depicted shall have its full value in the finished figure. Too much
realism in draperies with consequent under-cutting is to be avoided, and
the inclination of all but the high-temperature glazes to leave prominent
parts and pool in hollows must be heeded. Sharp edges are always bad, and
projections that are liable to crack in the fire or break at a touch are a
fruitful source of loss, and are, at the best, doubtful craft. It is quite
possible to produce delightful figures glazed with low-firing glazes, and
where a wide range of colour is desired, they are the only glazes
available. But for delicate modelling, where colour is a secondary
consideration and where refinements may be obscured by too much gloss, the
grand feu porcelain or salt glaze are the best and only alternatives.

But each man to his taste. We will start with a simple _two-piece_ mould
for pressing. Small objects, not necessarily figures, may be modelled in
the round, being designed therefore without under-cut to _pull_ in two
halves. They should be highly finished and then biscuited. The fired
original is then shellacked or oiled and carefully bedded in clay up to
the halfway line. If the figure be first dusted with French chalk, it will
leave the clay without trouble. Little walls being built, the first half
is then cast. When set, the biscuit figure is removed, the sides of the
mould trimmed, the joggles cut, and the figure fitted back. The sides are
carefully clay washed or oiled and the second half of mould cast. When
set, the two halves are gently pried apart and a groove hollowed out all
round the inner edge of the mould. (Figs. 58 and 59.) This groove is for
the reception of any surplus clay that would otherwise squeeze between the
two parts of the mould and prevent their perfect adjustment. To make a
_press_, each half of the mould is carefully filled with clay, well
pressed in. Then they are applied and firmly squeezed together, until the
two halves fit exactly. The press is then removed and trimmed up.

[Illustration: FIG. 58--FIGURINE FOR TWO-PIECE MOULD WITH BACKPIECE IN
POSITION.]

The second essay might follow the lines of the statuette here illustrated
for the three-piece mould. A decorative treatment, giving stiff lines and
a simple silhouette, is chosen. The hands are concealed, and the face, the
only flesh showing, clearly cut out by the costume. The section shows the
comparative depth of the folds in the drapery. Three pieces only were used
for the mould, indicated by the illustration. (Fig. 63.)

In moulding from plaster or biscuit the model must be absolutely
non-absorbent and should be carefully treated with shellac, beeswax
dissolved in turpentine, or parting. Beeswax is best for fine work and
should be applied very thinly and repeatedly. Clay originals need no
preliminary treatment, if the clay is still plastic.

[Illustration: FIG. 59--SECTION OF TWO-PIECE MOULD FOR PRESSING. SHEWING
GROOVE FOR RECEPTION OF SURPLUS CLAY.]

The divisions of the mould being decided upon, plastic clay is rolled out
thin, cut into strips, and built round the section, as shown in the
illustrations. (Figs. 60 and 61.) The exposed figure within the clay walls
is then very slightly filmed with olive oil. The plaster is then mixed and
thrown on or poured. The walls should stand out at right angles to the
circumference of the figure or so nearly as the exigencies of the figure
permit. They should be buttressed where needing support, and be deep
enough to give a good thickness to the mould. When the plaster sets, they
may be removed, and when quite hard, the plaster itself detached. This
comes away quite readily from the clay, but is apt to hold on plaster or
biscuit. A little water dropped from a clean sponge onto the cleaving line
will often release the two parts.

[Illustration: FIG. 60--CLAY WALLS FROM FRONT--Saint George Statuette.]

[Illustration: FIG. 61--CLAY WALLS BUTTRESSED AT BACK.]

The model is cleaned up and the sides of the first section trimmed,
slight joggles made where they will not bind, and the edges carefully
shellacked or claywashed. (Fig. 62.) Model and section are then fitted
together and the next section made in a similar manner, except that only
one wall of clay will be built. The second section is treated in the same
way, and for the last piece the clay wall is unnecessary, the plaster
being poured directly in between the two other sections. Where the plaster
has to be sprinkled on, or there is any danger from splashes, the exposed
parts of the model should be protected with soft paper.

[Illustration: FIG. 62--FIRST PIECE OF MOULD.]

The last piece being set, the original is removed, the mould assembled,
trimmed, or fettled, tied up, and set to dry. The casting, or pressing if
it be large enough, is proceeded with as before described, the slip being
poured in at the base. When removed from the mould, the open base of the
cast may be closed with a thin slab of clay slip poured on to a plaster
bat and allowed to set for that purpose. When tough, the figure should be
touched up with skill and reticence. Finally, a little hole is made in
the closed base and another as inconspicuously as may be in the back of
the head, to prevent blowing in the fire.

[Illustration: FIG. 63--SECTION OF A PIECE MOULD & RETAINING CASE WITH
FLAT TOP TO FACILITATE PRESSING.]

With more complex figures many more pieces will be needed for the mould.
They are made in the same way, but are carefully trimmed and then encased
in an outer frame or jacket of plaster. (Fig. 63.) Large figures should be
pressed; the head first, the different sections of the mould being fitted
into the containing case as the work progresses. More retouching is needed
with pressed figures, but the time spent is well spent, for they possess a
substance, and when retouched with art, a character, that is lacking in
the more fragile cast.

[Illustration: FIG. 64--SECTION SHEWING DEPTH OF FOLDS IN DRAPERY.]

[Illustration: FIG. 65--Early Greek Kiln.]



                               CHAPTER XV

                                 KILNS

  “By many long, laborious, and chargeable experiments he hath found
    out.”

                    --Extract from an old potter’s patent.


What must be the first representation of a kill, or kiln, is found at Beni
Hassan. It appears to be square in form, and the potter is shown feeding
the fire at the base. In the same illustration he is depicted unpacking or
drawing the ware from the top. The cut from the Greek Hydra gives a very
similar kiln, but a vessel in the museum of Berlin shows one with a
beehive shape.

The kilns left scattered about Europe by the Romans were usually of this
domed kind, circular in plan, with one fire hole. The floor of the kiln
was of pierced slabs, and the flames issuing thence enveloped the ware
piled within and escaped through a vent in the top. The packing and firing
is described in _Ceramic Art in Great Britain_, by L. Jewitt, F.S.A. It
fully explains the trepidation of the old potters, who, before each
firing, were wont to consult the moon and stars and evoke the aid of the
gods. This is happily set forth in Cowper’s translation of one of Homer’s
epigrams, wherein he expresses the pious hope that if the false potter
“stoops to peep into his furnace, may the fire flash in his face and
scorch it”; a risk often faced by potters, false or true!

The smothering, or reducing, as then practised, was similar to the
_lustring_ methods used in Italy in the sixteenth century, or in the
manufacture of the _blue_ bricks to-day. The Japanese and Chinese built
small kilns in tiers on the side of a hill. Starting with the lowest, the
waste heat was utilized to warm up the kiln above, thus saving time and
fuel. The Chinese used heavy saggars, and specimens of these with portions
of melted pots still adhering to them attest the enormous heats to which
they frequently attained.

Modern kilns subdivide roughly into biscuit, glost, and enamel. The first
is used for firing the green or clay shapes, the second for the hard fire
of the glazed ware, and the last-named for fixing on the added decoration.
Sometimes a kiln is used for the double function of biscuiting and
glazing.

Of modern kilns the one still most widely used approximates to the
bottle-shaped, simple, up-draught kiln. It contains one or two chambers
with hatch for entry, flue or chimney, and anything from three to nine
fire holes. The section of such a kiln is here shown and represents a fair
average up-draught kiln (Fig. 66), variants of which type are working in
most pottery districts to-day. In these kilns the flames rush in at the
fire holes, play on the built-up _bungs_ of saggars, and escape through
the top vent. In a two chamber kiln, as sometimes used for porcelain, the
glaze is put in the lower chamber to receive the hottest fire, the biscuit
in the upper getting a gentle fire. Where the fire enters directly into
the kiln in any large volume, _bags_ or small chimneys are built up inside
the mouths to save the saggars from the worst of the fire. Of late the
single-chamber, down-draught kiln has come into favour, as it is easily
packed and economical of heat. Bags of firebrick protect the saggars from
the roughest fire and direct the flames to the crown of the chamber, from
which point they descend to pass out through flues in the floor of the
kiln. (Fig. 67.) Biscuit ovens are often of this type, either domed or
flat arched.

[Illustration: FIG. 66--UP-DRAUGHT KILN.]

[Illustration: FIG. 67--DOWN-DRAUGHT KILN.]

The most recent innovations are gas and oil kilns. They require
comparatively little manual labour in the firing, are easily regulated,
and the waste heat is frequently used for secondary purposes. Their
freedom from smoke and their economy of labour and money must eventually
render the other types obsolete.

These large kilns are strongly banded with iron supports designed to
prevent too much loosening of the walls when expanded by the great heat. A
very important point is the draining of their site, as large kilns tend
to attract moisture, and the presence of steam in a kiln is productive of
much damage.

[Illustration: FIG. 68--ENAMEL OR MUFFLE KILN.]

Enamel kilns are used for the final processes where the glazed pot is
painted with over-glaze or enamel colours. They are of no great size and
are made of fire-clay slabs or even iron plates when the enamel is soft.
The flames play all round the muffle or fire-clay box during the firing,
but no flame or fume is allowed access to the inside. (Fig. 68.)

In packing a kiln with biscuit or glaze much care, thought, and expedition
have to be exercised. An experienced setter is essential in a factory if
the pots are to have every chance in the fire, for all kilns vary and have
their hot and _cool_ corners. First, the floor is well bedded with quartz
sand or flint that will not vitrify but will provide a good setting for
the bottom saggars. These saggars are fire-clay _boxes_, round or oval,
rarely square, and without lids, in which the pots are placed. Piled one
above another they form the _bungs_, the bottom of one supplying the top
of that beneath. These bungs are built at intervals that permit the flames
to penetrate between them and give a good even fire all over the chamber.

In actual practice some parts of a kiln are hotter than others, and it is
here that a good setter shows his capabilities, setting the thin wares in
the softest places and putting the heavier biscuit or hard glaze in the
hottest corners. With biscuit the setting is not difficult except where
delicate or friable ware may need very careful bedding and propping. With
clean saggars the biscuit may touch the sides, and a competent man will
pile an enormous amount of biscuit into a kiln without risk. In the glost
kiln the ware requires gentle handling and must touch nothing but the spur
or support. The saggars are usually given a saggar wash of lead and stone
to prevent them absorbing glaze from the wares, for a glazed pot placed
too near a raw saggar is very likely to come out with a thin or dry patch.

When the pot is firmly placed on its stilt, a roll of _pugging_ is placed
round the rim of the saggar; this provides a firm bed for the next above
it and also stops the entry of dust and flame. This pugging is made from
clay or marl mixed with ground sherds, sieved gravel, or some non-vitreous
dust to prevent it sticking to the saggars. The plugging is made malleable
with a little water and rolled out by hand or pressed through a die. It
will readily be seen that a carelessly built bung of any height may slip
in the stress of firing, and its fall would most likely involve others,
whilst any slight movement may be sufficient to cause a vase to topple off
its stilt. In a down-draught kiln the bungs over any vent must be raised
on fire tiles to permit the escape of the flames. When all the bungs are
filled up and piled in position, the trials and cones placed, the hatch is
bricked up. Spy holes are left where necessary, and the whole well clammed
to prevent the loss of heat during firing. When fired, the hatch may be
very gradually loosened to accelerate the cooling.

[Illustration: FIG. 69--DOWN-DRAUGHT KILN.]

The fireman’s job is one of the most arduous and important of all the
prolonged processes of potting. Coming as it does at the end, it may make
or mar kilns of great value, and it requires more than ordinary judgement
and nerve. The chief troubles arise from bad or irregular draught or
impure fuel. They express themselves in the form of clinkered holes,
excessive smoke, and irregularly fired or sulphured ware. The term
_sulphured_ is applied to pots that come out gloomy or dulled and is said
to be equally due to a reducing fire or an oxidizing one. In the former an
insufficiency of air causes excess of carbon in the kiln and the
absorption of oxygen from the glaze. In the latter an excess of air
(oxygen) allows sulphur vapour, if present, to attach itself to the glaze.

The fire bars, fire holes, and flues must be kept clear and the fuel
carefully selected if these things are to be avoided. The aim, as
previously stated, is a gradually increasing fire, sharper towards the
finish. For this purpose some potters finish off with wood which gives a
long flame free from sulphur and clears the glaze. Even when sulphured, a
clear flame at the finish will remove many ill effects. The baiting should
be fairly heavy at the start, lighter and more frequent towards the
finish, when smoke in any quantity should be avoided.

For temperature gauges, the cones previously described are used and should
be placed in an average place, screened as much as possible from draught
or flame. Small sight pots and glaze rings placed near the spies can be
hooked out and examined and are valuable aids, but their exposed position
and the corrosive action of the flames must be taken into account.
Pyrometers are also used, but with all these aids the experienced fireman
pays due regard to sight and colour.

For a craftsman, the kilns that have been described are unsuitable on
account of their size, if they are not altogether beyond his means. But a
kiln of some sort is indispensable to a potter. The craftsman is nothing
if not inventive. Small trials can be fired in crucibles in an open fire
or on a gas ring. I have heard of some preliminary success with a gas
cooker, discounted later by a frontal attack from the cook. Considerable
knowledge can be gained from small, easily constructed, experimental
kilns.

The small trial kiln shown (Fig. 70) was constructed with a stout old
_crock_, over which was built a core of bricks plastered with marl. The
fire was started at each corner at the bottom, and when well alight, fed
from the top with coke. A small spy at one corner closed with a piece of
biscuit gave some idea of the progress of the firing. This, of course, had
to be practically rebuilt at each firing, but as a makeshift was quite
satisfactory.

[Illustration: FIG. 70--CROCK WITH IMPROVISED SPY HOLE. CONE INSIDE.]

[Illustration: FIG. 70A--CROCK BRICKED OVER & PLASTERED WITH MARL.]

The gas and oil kilns described in Chapter IX are excellent as far as they
go, and indeed the only practicable kind for indoor schools. But their
restricted size soon becomes irksome to a craftsman, whilst the expense of
firing makes only the finest work remunerative. For over-glaze work they
are excellent, but for some reason glazes fired in them seem to lack some
of the richness and maturity the same glazes exhibit when fired in the
slower and more soaking fire of a brick kiln. The dug-out kiln here
depicted (Fig. 71) would be quite suitable for summer schools or for a
craftsman making soft peasant pottery. The section and sketch will
indicate its construction. The materials are hard bricks and stout old
boiler plates, or sheet iron. To pack or unpack, the middle section of the
roof would have to be removed each time, and all glazed pots would need
protection from scalings and gravel from above. The roof will sag at any
big heat, and if of thin iron, will need propping. The firing would be
done with soft coal or wood; a very slow start, with a brisk draught and a
long flame at the finish.

[Illustration: FIG. 71--“DUG-OUT” KILN OF COMMON RED BRICK.]

Of course the front will be hotter than the back, but if saggars can be
obtained, the glaze may be placed in them to the front with the biscuit
protected behind. Clay shapes fired up at the front may bend towards the
fire, and any broken crocks should be used to screen them.

The making of rough saggars is not difficult if a supply of fire clay is
to hand, or clay and grog will serve at a pinch. The clay is rolled out
and the saggar stuck up, much as described on page 32. Every joint must
be carefully welded and the whole thoroughly dried. Then they are fired up
in the kiln, _very_ gently at first, and carried up to a temperature
considerably above that which they will be subjected to when in use.

[Illustration: FIG. 71A--SECTION OF “DUG-OUT” KILN.]

For small trial crucibles ordinary clay mixed with pitchers and powdered
coke proves satisfactory; the coke when fired out renders the body porous
and the heat penetrates more swiftly.

To construct the muffle kiln shown at Fig. 72 the aid of a competent
bricklayer would probably be required. In this kiln glaze and biscuit
would fire up without saggars, but will take rather longer. The plan and
elevation of this particular kiln are given with all reserve. The design
would probably require considerable adjustment and modification before
complete satisfaction was obtained.

[Illustration: FIG. 72--SECTIONS OF MUFFLE KILN TO SHEW SUPPORTS. FLUES.
ETC.]

A down-draught kiln, although more difficult to construct than an
up-draught, is more economical in the end and does its work more evenly.
For the benefit of those that may like to build a small and moderately
cheap kiln drawings are here given. This kiln was built by me when I had
very little practical experience of kilns other than gas, but it served
its purpose well. It was not banded, but this is essential if the kiln is
to stand hard and frequent fire. Firebricks were used for the fireholes,
flues, floor, core, and dome; strong stock bricks for the rest. The glazed
ware, which was fired harder than the biscuit, was saggared in bungs as
usual up to about five feet; the biscuit piled on top and protected by old
saggars and cracked pots from the roughest fire. There were no bags in
this kiln, but the saggars used were very strong and had stood a much
greater heat than that to which they were subjected in this kiln, so that
they showed very little wear or tear after twenty firings. The stack of
sixteen feet gave a good sharp draught, increased if necessary by the
addition of an iron chimney and regulated by an iron damper. A wind screen
or _hovel_ is advisable for rough nights, and some sort of roof is
necessary to protect the crown from the weather. It is important to have
the arch of the hatch very strongly built, as it has to stand a lot of
strain, and an iron support too near the fire soon corrodes and needs
replacing. Another essential is that the site be as dry as possible and
the foundation made solid with concrete; otherwise even a small kiln is
liable to settle and crack. With a little extra expense a kiln of this
kind could be banded round the impost and fireholes, thus considerably
prolonging its life.

[Illustration: FIG. 72A--PLAN SHEWING ARRANGEMENT OF FIRE TILES FORMING
MUFFLE.]

[Illustration: FIG. 72B--MUFFLE KILN BUILT OF FIRE TILES, FIRE BRICKS,
AND COMMON REDS.]

[Illustration: FIG. 73--POKER. SLICE. TONGS.]

In firing this kiln about half a ton of coke and three quarters of a ton
of good hard coal, giving a long flame, was used. Coke for the slow fire
was first started on the bottom and maintained for sixteen or eighteen
hours, lifted up on to the bars for another six or eight hours, when the
saggars would begin to show signs of colour. The coal fire was then
started about the 24th or 25th hour and continued another 18 hours, more
or less, according to the varying conditions, making in all some 40 or 45
hours. This gave a very evenly graduated heat from cone 1 at the base to
cone .03 at the top. Bags were tried experimentally, but whilst giving a
more uniform heat, took much longer to fire up. At the finish of the
firing the fireholes were bricked up, the damper closed when the fires
died down. In about 24 hours the vent and the hatch were eased a little
at the top, and in 48 hours it was pulled down and the drawing commenced.
Packed with the hard glazes at the bottom and the soft at the top this
kiln answered excellently for the purposes for which it was required.

[Illustration: FIG. 74--SAGGAR WITH A POT INSIDE.]



                              CHAPTER XVI

                    THE EDUCATIONAL VALUE OF POTTERY

  “The principal point in Education is that one’s knowledge of the
    World begins at the right End.”

                                           --SCHOPENHAUER.


The study of the fictile art of the potter, even from the theoretical side
alone, cannot fail to quicken and broaden education. The antiquity of the
craft, stimulating research amongst the records of ancient civilizations,
brings to light customs and habits bearing very closely upon the earliest
struggles of man to emancipate himself from mere brute surroundings. The
primitive decorations rudely scratched on clay vessels antedate and
forecast the hieroglyphic and sign languages of all nations.

It would be but hyperbole to claim that without clay the Mosaic tablets
would have remained unwritten, but indubitably the clay cylinders of
Assyria gave a strong impulse to the development of ciphering and writing
and the spread of learning,--an impetus not to be derived from the
obstinate granite medium so generally employed by the Egyptians.

It is this amenable ductile quality, so easily receptive of the most
emotional touch, that has made and still makes clay such an admirable
medium of expression for the young,--whether young in the history of the
world or young in actual years. And this malleability is accompanied by a
tenacity that permits slow building up, remodelling, and high finish,
suitable to work of the most painstaking character. To this is added the
fixed, unalterable quality imparted by fire, so that pottery more than any
other craft preserves an imperishable record of the ages.

This positive chronicle is valuable alike to the savant or the student.
Indeed the most trivial child’s toys of the Hellenes, the quaint water
pots of the Peruvian peasant, or the unassuming tea bowl of the esoteric
followers of Riku may chance to convey to the sincere student a clearer
idea of the habits and thoughts of their producers than many a pedantic
treatise or translation.

                                            “So lively shines
      In them Divine resemblance and such grace
      The hand that made them on their shape hath poured.”

                                                 --MILTON.

Coming down to points in close contact with the curricula of schools, we
all subscribe to the dictum of Ruskin that “Everyone, from the King’s son
downwards, should learn to do something finely and thoroughly with his
hands.” What then more suitable than sympathetic clay wherein to fashion
the first fancies of the child mind. It is a medium at once attractive and
easy to mould, giving a tangibility and reality to forms and things that
can never be obtained by drawing or painting. Then the limitless uses to
which clay is put, and, with the development of hygiene, increasingly will
be put, have the closest bearing upon the everyday life of the child. They
are intimately connected with other studies that cannot fail to be
rendered more attractive by working in clay.

But clay work is a branch now so universal that it seems unnecessary to
dwell upon its advantages to the kindergartener.

The valuable remedial effects of clay work upon the defective are perhaps
less widely known. The manipulation induces a most beneficial
concentration and provides a fine discipline without a trace of inimical
restraint. Turning to higher grades, the use of clays should foster an
interest in the formation, composition, and disintegration of rocks, and
in the properties of the products so engendered; in short, a liking for
geology.

With the making of simple glazes and colours will awaken an intelligent
curiosity concerning the nature of minerals and metals, their actions and
reactions in the fire; a lively sympathy only awaiting a touch to turn it
into a love for chemistry and physics. Then as power and ambition and
craftsmanship develop, there must needs be a study of the history of
ornament. This impinges too closely upon history and geography to fail to
increase the student’s attraction towards these more remote but allied
fields.

Finally, is it not in the realm of æsthetics that there looms the ultimate
reward? The proper pursuit of pottery must eventually lead us “towards
that idealization of daily life ... and the road that connects the love of
the beautiful with the love of the good is short and smooth” (President
Eliot). In the hurried curricula of to-day art plays a rather sorry part.
Little time indeed is left for contemplation, for the realization of all
that beauty and harmony in our surroundings may mean to us in our everyday
work.

The making of a bowl, with the concentration required to shape it in a
manner at once beautiful and serviceable, must quicken the perception of
beauty and sharpen the quality of judgement, not only for things fictile,
but in far wider fields. Thus the things of everyday contact--the
tableware, the chairs, the doors, the windows, pictures, ornaments,
hangings, and fittings--will all come in for intelligent scrutiny and
criticism. This in turn will be carried on and over into matters civic.
This must result in a careful estimation, selection, and appreciation of
our surroundings, bringing them into harmony with our cultivated thoughts
and so enabling us to get through the day’s work with the least amount of
useless friction and with the greatest possible measure of enjoyment,
well-being, and well-doing.

[Illustration: PLAN OF A SMALL POTTERY.]



                               APPENDIX I


                             THE EQUIPMENT

The divinity that presides over potting is an expensive as well as an
exacting mistress. The equipment of even a small pottery is,
unfortunately, a matter of considerable expense. Try it from whatever
angle we may there is the cost of the kiln to be faced, besides a host of
other small but cumulative expenses. The first essential is, of course, a
roomy workshop with if possible a top as well as a side light. If the
craftsman means business, he should remember that the initial cost of a
kiln is often in inverse ratio to its upkeep. If he would aspire to big
things, full-bellied pots, plaques, reliefs, and figures,--and every
craftsman would,--a brick kiln will be wanted. One holding a dozen saggars
could be built, but where some experience has been obtained with materials
and processes, a larger one would be more economical. With oil or gas
kilns of the ordinary school size the cost of firing and the extra time is
proportionately too great to permit of any but comparatively high-priced
pots being turned out. This may serve in some cases, but usually it is not
practical potting where a livelihood has to be obtained. Where only the
painting is to be fired on, an oil or gas kiln is exactly what is wanted.

In this appendix is given a plan of a workshop that has all the equipment
necessary for the whole-hearted pursuit of the craft. In such an one a
good craftsman, capable of modelling and painting decently a figure or a
panel, a good thrower, and a handy boy could work wonders. They would be
capable of turning out a surprisingly wide range of “pots”: jugs, mugs,
pots, bottles, bowls, buttons, dishes, plaques, panels, vases, tiles, and
statuettes,--useful and beautiful things. Anything in fact worth doing can
be done except fine tableware or those articles that by their nature
demand more mechanical accuracy than is possible, or even desirable, for a
craftsman to exhibit. Where much plaster turning for moulds was attempted,
a lathe would be required; ordinarily the hiring of one should be
practicable and expedient. Where only built or cast shapes were attempted,
the wheel and its long years of drill might be dispensed with, and it is
possible, with strong individual work of high finish and fine quality and
the consequently restricted output, that an oil or gas kiln would give
economically practicable results. Between the kiln for firing decoration
simply painted on the ready-made shape to the full equipment here
described will be found several modifications, but to try the craft
without a kiln of some sort is an imbecile proceeding.

  Small brick kiln supplied with saggars.
  Small muffle kiln--oil or gas--for over-glaze and lustres.
  Small enameller’s kiln for firing quick trials.
  Kick wheel, and tools for throwing.
  Clay bin, zinc-lined.
  Damp-box.
  Drying cupboard.
  Plaster bin.
  Pot boards and brackets.
  Table, strong and heavy.
  Clay: white, red, buff.
  Plaster.
  Glaze materials.
  Oxides, lustres.
  Under- and over-glaze colours.
  Modelling tools, callipers.
  Painter’s outfit.
  Brushes, straight-edges.
  Shellac, beeswax, French chalk.
  Gum arabic and tragacanth.
  Glaze tubs, teak.
  Sieves, glaze and slip, Nos. 80, 100, 120.
  Buckets.
  Bowls, enamelled and earthenware.
  Small porcelain ball mill, hand or power.
  Spray and pump (respirator).
  Small outfit for carpentry.
  Files, sheet iron, and zinc, wire and cutters, cords, sandpaper.
  Benches and shelves ad lib., odd cupboards, chairs, etc.,
  Shovels and slicer for firing, tongs for trials.
  Two large tubs and rubber tubing.
  Sand and flint.
  Spurs, props, fire tiles.
  Tile boxes.
  Disc (emery) for grinding.
  Small pestle and mortar.
  Jugs and funnel.
  Potter’s knife, sponges.
  Whirler.
  Turning tools and lathe.
  Temperature indicators.
  Oil can, oil, waste.
  Callipers and compass, rulers.

Most of this equipment has been previously described and needs no further
comment.

The pot boards and brackets are simple but indispensable devices. The
boards are about six feet long, iron shod or cross battened to prevent
warping, and six or nine inches in width. The brackets of any serviceable
kind are fixed to the wall at convenient distances. When throwing,
turning, or glazing, the pots are stood on one of these boards to dry, and
each board as filled is slipped onto the brackets. Thus the pots may be
carried about to the kiln, drying cupboard, or glaze tubs without loss of
time or frequent handling.

The table must be stout enough to withstand the heavy work of wedging and
should have a top of hard wood. Teak or hard-wood glaze tubs have the
advantage of not breaking either themselves or pots accidentally knocked
against them. Further, some glazes stick badly to porcelain or enamel
tubs.


                     EQUIPMENT FOR A SMALL POTTERY

In the small pottery plotted here, the equipment and arrangement were as
follows:

  An anthracite stove with the pipe running into the large room
    warmed the workshop in winter, but no wet or half-dry pots were
    left where the frost could get at them.

  The glaze materials, oxides, colours, painting paraphernalia,
    finished pots, trials, and trial kiln were in the small room.
    The wheel had a good top and side light.

  The drying cupboard, plaster bin, and moulds were at the end
    nearest the stove; the clay bin, damp-box, and sink farthest
    away.

  All the walls were copiously supplied with brackets and shelves
    and handy benches.

  Outside, in a well-built lean-to, was the muffle kiln for onglaze
    and lustre decoration.

  This was well bracketed and shelved for the biscuit, and here was
    done the glazing, handy for packing in the brick kiln just
    outside. This was protected from the weather and other lean-to’s
    held the saggars, coke, and coal.


                         EQUIPMENT FOR SCHOOLS

The teacher with ample funds and a free hand will find the previous
chapter all-sufficient, but in many cases the purchase of a kiln will
nearly exhaust the allowance and the rest of the equipment becomes
sketchy.

The indispensable appliances are as follows:

  A kiln, with fire tiles or shelves, props, spurs, and stilts,
    etc., for packing. A good clay bin and sieve for slip (No. 80)
    with a tub and two pails.

  Scales and weights, pestle and mortar and glaze lawn (No. 100),
    shot for weights.

  Plaster, for drying bats and working discs.

  Large drip pan and three round pans.

  Several jugs and bowls.

  Spoons (wooden), knives, and big brushes.

  Oil, gum, boards, strips, rolling pin.

  Hammer, saw, iron straight-edge, sponges.

  Glass slab and muller, palette knife and brushes for painting.

  An atomizer or spray pump.

  Glaze materials:

  Kaolin, China stone, flint, silver sand, whiting, felspar, borax.
    A supply of ground pitchers and grog, cones.

  Metallic oxides:

  Tin, white, oxide of, iron, copper, manganese, cobalt, etc.

  Under-glaze colours to taste.

  Glass jars with lids to contain materials. Gummed labels, India
    ink.

For a school in the country or where ground is available, a kiln like the
one shown at p. 164 should be practicable. It costs very little to build
or to fire. Next comes the question of the clay. This is one of the most
abundant of nature’s materials, and almost any river bank or creek will
supply clay of some kind. Any sort of clay near to hand should be
thoroughly tested before going to other or distant sources.

The clay should be dried, then broken up with a hammer, and mixed with
water, and the resultant “slurry” passed through a sieve (No. 80). The
slip is allowed to settle and the water siphoned off. The thick slip is
then dried on the plaster bats until stiff enough to work up between the
hands. From this clay a tile, a plate, and a vase should be made and
fired. If the pieces stand a fire of about 1100° (cone .03) without
buckling, splitting, or crumbling, the clay should do quite well for
school work. Possibly when screened fine enough for working, the clay may
be too rich or _long_ and will split at a moderate fire. Then the
screenings might be pounded in the mortar, passed through the sieve, and
added to the slip. Again, ground pitchers, fine grog, kaolin, or calcined
flint could be tried as stiffening agents. In the unlikely event of the
clay being too refractory or _short_, a portion of rich, fusible, or _fat_
clay might be added, or the addition of powdered spar tested. (See chapter
on Clays.) The colour of the body will hardly matter for schools; indeed
a brown, red, or cane-coloured clay will give better results than a
staring white paste, when working out simple school problems.

Where necessary, tin glaze could be used for a white ground, or an engobe;
that is, a dip of white clay slip over the coloured body. For glazing, a
leadless glaze is strongly to be advised. Lead is often indispensable to
the craftsman, and with care need not become a danger; but in schools a
lead glaze is positively harmful.

A glaze with a borax base, if ground dry and mixed with water and
re-ground before sieving, will give little trouble if used immediately. It
will answer for all grade work and may be used for spraying, dipping,
pouring, or painting, with absolute safety.

The ground pitchers and grog may be obtained by pounding up broken biscuit
and pieces of fire tile, respectively. This, and the glaze grinding, is,
of course, laborious work, and suggests correlation with the Physical
Education Department. The drip pan and the round tins make excellent
moulds for casting drying bats and working bats.

For casting purposes plates and shallow bowls may be moulded in one piece
as described, p. 26. If no lathe be handy, glazed vases may be used as
substitutes, the “waste” being added in plasticine to the neck and base.

For tile-making, strips nailed on a stout board will serve in place of
tile boxes. The clay is rolled out on cheesecloth with a rolling pin.
Various other expedients for drying cupboards, damp-box, etc., will
suggest themselves as the course develops.

The above equipment need not be very costly. With it the students should
be capable of producing all kinds of tiles, built, pressed, and cast
shapes, decorated in relief, with inlays or in colours or glaze.


                     SIMPLE RAW GLAZES. COLOURLESS

  ===================================================================
  NO.   |MATERIALS      |PARTS| SIEVE NO.|CONE| METHOD OF USING
  ------+---------------+-----+----------+----+----------------------
  I     |Lead oxide, red| 50  |100. Mesh |.03 |Applied evenly
  Glossy|China stone    | 30  |          |    |with a brush to
        |Flint          | 10  |          |    |the _green_
        |               |     |          |    |shapes. Fired very
        |               |     |          |    |slowly. Earthenware
        |               |     |          |    |body.
        |               |     |          |    |
  II    |Borax          | 70  | 80. Mesh | 2  |Green shapes
  Glossy|China clay     | 10  |          |    |dipped thick
        |Felspar        | 75  |          |    |and slowly fired.
        |Flint          | 20  |          |    |Stoneware body.
        |Whiting        | 25  |          |    |
        |               |     |          |    |
  III   |Borax          |360  |100. Mesh |.03 |Ground dry for
  Glossy|Silver sand    |160  |          |    |1/2 hour Wet for
        |China clay     |120  |          |    |1-1/2 Used when
        |Whiting        | 20  |          |    |fresh on biscuit
        |Flint          | 10  |          |    |(earthenware
        |               |     |          |    |body) for under-glaze
        |               |     |          |    |painting.
        |               |     |          |    |
  IV    |Lead carbonate |130  | 80. Mesh |.04 |Used with metallic
  Glossy|Calcined kaolin|150  |          |    |oxides for
        |Flint          | 50  |          |    |simple colours on
        |Felspar        | 50  |          |    |earthenware
        |Whiting        | 10  |          |    |body; both green
        |Zinc oxide     | 10  |          |    |and biscuit.
        |               |     |          |    |
  V     |Lead carbonate |375  |120. Mesh |.04 |Used thick on
  Matt  |Kaolin         |210  |          |    |hard white
        |Felspar        |175  |          |    |earthenware (CC)
        |Flint          |120  |          |    |body.
        |Whiting        |105  |          |    |
        |Zinc           | 25  |          |    |
  VI    |Lead carbonate |120  |100. Mesh |.02 |Used thick on
  Matt  |China clay     | 50  |          |    |stoneware body.
        |Felspar        | 80  |          |    |Coloured with 3
        |Flint          | 15  |          |    |to 7 per cent of
        |Whiting        | 45  |          |    |glaze stains or
        |               |     |          |    |U. G. colours.
        |               |     |          |    |
        |               |     |          |    |The proportion
        |               |     |          |    |of lead and whiting
        |               |     |          |    |may be varied
        |               |     |          |    |as found
        |               |     |          |    |expedient.
        |               |     |          |    |
  VII   |Borax          | 70  |          |    |
  Enamel|Lead carbonate |300  |          |    |
        |China clay     | 50  |80. Mesh  |.07-| Used with various
        |Felspar        |120  |          |.05 | combinations
        |Lynn sand      | 50  |          |    | oxide, and iron
        |Tin            | 40  |          |    | oxide and copper
        |               |     |          |    | carbonate, giving
        |               |     |          |    | wide range of
        |               |     |          |    | blues and greens.
        |               |     |          |    | On stoneware
        |               |     |          |    | body.

All the above colourless glaze masses may be coloured with combinations of
the various metallic oxides, or from 3 to 7 or even 10 per cent of glaze
stains or under-glaze colours.



                              APPENDIX II


                                GLOSSARY

  =Alumina, or Oxide of Aluminium=, is one of the most abundant of
    earths. Combined with silica it is the chief constituent of
    kaolins and China clays. It imparts refractory qualities to
    clays and is an indispensable ingredient of pure glazes. Pure
    alumina or calcined Aluminium is a chemical product.

  =Ammonia.=--A volatile gaseous matter, found in some clays.
    Alkaline in action.

  =Antimony.=--A silver-white metallic element, used with other
    oxides as a colourant or to give opacity in glazes.

  =Arsenic.=--A non-metallic volatile element, used in glaze making.

  =Barytes.=--A heavy spar used with clays to introduce density and
    vitrescence.

  =Bauxite.=--A very aluminous earth, used in preparation of pure
    alumina and to render clays refractory.

  =Boracic Acid.=--The natural and, usually, impure product (boric
    acid being free from chemicals).

  =Borax.=--The combined chemical product of soda and boracic acid.
    Used as a strong flux in glazes.

  =Calcined Bones.=--The residuum of burned bones, used to stiffen
    artificial porcelain.

  =Calcined Kaolin.=--Kaolin after it has been subjected to heat to
    drive off the water combined with it.

  =Calcium Carbonate (Whiting).=--Found as a white rock, and ground
    to pure powder. Used with clays for soft bodies. Gives
    durability to glazes.

  =Calcium Oxide (Lime).=--A widely distributed earthy matter.
    Imparts fusibility to clays, in nearly all of which it is
    present in varying proportions.

  =Chrome, Oxide of.=--Used in making greens, browns, and blacks.
    Stands a high fire.

  CLAYS:

  =Ball Clay.=--Blue and black. Very plastic clays. Used with
    non-plastic materials, such as flint, stone, felspar, or
    whiting, to form fine earthenwares.

  =Cane and Red Clays.=--Clays coloured by the presence of ferric
    oxide, and used extensively for bricks, terra-cotta tiles, and
    common pottery.

  =China Clay.=--A yellowish-white, non-vitreous clay, product of
    the decomposition of granitic or felspathic rocks. Cornish China
    clay is exceptionally white, pure, and plastic. It is widely
    used with China, or Cornwall stone and calcined bones, to make
    bone porcelain. Felspar is added to render it vitreous. Mixed
    with ball clays, pipe clays, flint, and stone, it makes the
    various classes of earthen and stone wares.

  =Pipe Clay.=--A very white, smooth clay. Less plastic than ball
    clays. Much used for making slips, engobes, and enamels.

  =Saggar Clays or Fire Clays.=--Coarse refractory clays
    strengthened by the addition of grog, used for saggars, fire
    tiles, and bricks.

  =Cobalt Oxide.=--The oxide of the steel-grey hard metal. Extremely
    valuable in pottery, making all shades of blue for under-glaze
    printing or staining. With iron or copper gives blue-greens.

  =Copper, Oxides of, and Carbonate.=--Red, green, and black oxides
    of copper have been of the utmost value to potters. They are
    used to produce green, blue, turquoise, red, and crimson. Its
    extraordinary changes in reducing or oxidizing fires are of the
    greatest interest to the experimenter.

  =Cornish or China Stone.=--A rock composed of felspar and quartz.
    Its vitrification (about 1400° C.) imparts hardness and density
    to China clays. It is a valuable constituent of glazes. First
    known as “moorstone” or “growan.”

  =Earthy Colourants.=--Rarely used in modern commercial pottery,
    except for salt-glazed jars, crocks, and peasant pottery.

  =Felspar.=--A fusible rock found almost pure or in combination
    with potash and soda, the greater the percentage of alkalies the
    more fusible being the spar. It is used to replace more
    refractory materials in clay and to stiffen glazes.

  =Flint.=--A pure silica with slight traces of calcium. Found in
    pebble form on seashores. Calcined and ground to a white powder,
    it is widely used to impart whiteness and strength to clays.
    Invaluable for bedding and packing in kilns. Used with the
    fluxes,--lead, borax, potash, and soda,--to make glazes and
    glass.

  =Fluorspar.=--A combination of fluorine and calcium, more fusible
    than felspar, and of a white colour, felspar being pink.

  =Galena.=--Lead sulphide, a highly poisonous material used on
    “peasant” pottery, giving a soft, yellowish, transparent glaze.

  =Gold.=--Used in solution for delicate purples and lustres.

  =Gypsum.=--When calcined gypsum becomes plaster of Paris, these
    two materials, together with the allied marble, limestone, and
    alabaster, are widely used in pastes (such as Parian), slips,
    engobes, and variously to impart fusibility or colour properties
    to glazes.

  =Iron, Oxides of.=--Have a wide range of colour, from yellow to
    purple. They are used to stain glazes and colour bodies. They
    impart fusibility to clays and are carefully excluded from fine
    white bodies.

  =Kaolin.=--A fine, white, very pure, and infusible China clay,
    almost pure alumina and silica. Chiefly used in the manufacture
    of porcelain and fine earthenware.

  =Lead (Oxides and Carbonates of). White Lead, Red Lead,
    Litharge.=--Are very widely used as a safe and cheap flux.
    Poisonous. It cannot be used in those glazes that have to stand
    a high fire.

  =Lime.= (_See_ =Calcium=.)

  =Lynn Sand.= (_See_ =Quartz Sand=.)

  =Magnesia.=--A white metallic element present in small quantities
    in most clays.

  =Manganese.=--The black and brown oxides of this hard metal are
    much used to stain slips and bodies, and to colour glazes brown
    or purple.

  =Marls.=--Amorphous deposits of lime, sand, and clay, very coarse
    in texture. Used in making saggars, drain pipes, and similar
    appliances.

  =Nickel.=--A hard metallic element, the oxides of which are found
    useful in preparing blacks, greys, and greens.

  =Nitre or Potassium Nitrate, or Saltpetre.=--A vitreous and
    aqueous compound, used in some glazes.

  =Plaster of Paris.= (_See_ =Gypsum=.)

  =Potash.=--Potassium carbonate or the leached ashes of plants.
    Used from earliest times as a powerful alkaline flux.

  =Potash, Bichromate of.=--Used for pinks and crystalline effects.
    Poisonous.

  =Quartz or Quartz Sand.=--Like Lynn or silver sand. This mineral
    is pure silica and free from lime, although the sands may
    contain some small percentage of iron. Used much like flint for
    bedding or with alkaline fluxes for the finest glazes.

  =Rutile. Oxide of Titanium.=--Used variously to impart a yellow
    tinge to porcelain, and colour and irregularity to some glazes.

  =Salt.=--Sodium chloride. Sometimes used in glazes, but best known
    in connection with salt glazing. It vaporizes at about 1200° C.,
    forming a silicate or hard, thin skin of glaze over the clay.

  =Silica.=--A hard, colourless crystalline element; found pure, as
    in quartz, or in combination with alumina and alkalies, as in
    all clays. Present in all glazes.

  =Soda. Sodium Carbonate.=--Product of the decomposition of salts
    with acids. It is a strong alkaline flux and much used in glaze
    and glass-making.

  =Silver Sand.= (_See_ =Quartz=.)

  =Tin, Oxide of.=--Used from the earliest times to impart opacity
    to glazes.

  =Tincal.= (_See_ =Borax=.)

  =Titanium.= (_See_ =Rutile=.)

  =Whitening.= (_See_ =Lime=.)

  =Zinc, Oxide of.=--A white metallic oxide; used to brighten and
    stabilize glazes and colours.


                             POTTER’S TERMS

  =Bags.=--Chimneys or walls of fire bricks built to protect the
    ware from flame.

  =Baitings.=--The feed of fuel during firing.

  =Bat.=--Any flat slab of plaster, biscuit, or fire clay.

  =Biscuit.=--The fired but unglazed clay.

  =Blowing.=--The shattering of the clay shape when biscuiting.
    Usually due to hurried firing or the sudden access of heat, and
    the consequent generation of steam.

  =Blunger.=--A machine for mixing clay.

  =Bungs.=--Piles of filled saggars.

  =Chuck or Chum.=--The cone or cap used to support shapes during
    turning on the lathe.

  =Clamming.=--The wet marl, sand, or siftings applied to cracks in
    the hatches or doors of kilns to retain the heat during firing.

  =Craze.=--The minute cracks that appear in a badly fitting glaze.
    When arrived at by design, as in some Chinese work, it is termed
    a crackle, but there is then no fissure.

  =Drawing.=--Unpacking the kiln after firing.

  =Engobe.=--A dip or outer covering of slip; usually applied to
    inferior bodies to improve their appearance.

  =Fat.=--Clays that are sticky or greasy are sometimes termed fat
    by potters.

  =Fettle.=--To touch up, and remove traces of seams, cast lines,
    etc.

  =Fluxes.=--Those materials which by their addition to paste or
    glaze render them fusible, although they may not always be
    fusible themselves.

  =Glost.=--The glazed ware, usually applied to the glaze in firing,
    as glost-oven.

  =Green.=--The clay shapes before biscuiting.

  =Jigger.=--The wheel on which shapes are moulded with the aid of a
    jolley or profile.

  =Joggle.=--The natch or key in a mould to insure correct
    adjustment and prevent slipping.

  =Lawn.=--The fine mesh gauze through which glazes are strained.

  =Long.=--A clay is termed long if very ductile and tenacious.

  =Muffle.=--Usually the fire-clay box or interior of a small kiln,
    but applied to any kiln to the inside of which the flames have
    no access.

  =Natch.= (_See_ =Joggle=.)

  =Oxidizing.=--The ordinary method of firing gives an atmosphere in
    which there is always sufficient oxygen to consume all the
    carbon or combustible gases. If oxygen is present in excess, it
    causes reactions known as oxidizing.

  =Pitchers.=--Finely ground biscuit. Added to some clays to
    increase refractories or porosity. Moulds made in such clays and
    fired are termed pitcher moulds.

  =Potsherds.=--Any broken biscuit or pot, sometimes used for
    pitchers.

  =Potting.=--A colloquialism used to designate the ceramic
    industry.

  =Pugging.=--The roll of infusible clay placed between each saggar
    when building bungs.

  =Reducing.=--The reaction that accompanies the introduction of
    smoke or gas containing carbon in a very finely divided state
    into a kiln during the process of firing glaze. Reduction is now
    widely employed in obtaining fine lustre effects.

  =Refractory.=--Hard, infusible.

  =Rich.=--Used of clays that are long and fusible, such as red
    clays.

  =Riffle.=--A grooved and toothed plaster tool of steel.

  =Saggars.=--Or seggers. The fire-clay receptacles in which the
    glazed ware is set during the firing.

  =Setters.=--Supports used when packing friable biscuit.

  =Short.=--A word used to denote a clay that crumbles or is
    difficult to pull up on the wheel.

  =Sieve.=--Sometimes called a lawn, more correctly a screen for
    clay or slip.

  =Slip.=--The sieved clay or paste in creamy liquid condition as
    used for slip decoration, engobes, or casting.

  =Slub or Slurry.=--Clay mixed with water but not sieved, as with
    slip.

  =Spy.=--The small hole, kept plugged, through which tests and
    cones are observed.

  =Stunt.=--Or dunt. To crack or split on cooling.

  =Turning.=--The shaving down of the clay shape on a lathe, to
    impart lightness and finish.

  =U. G.=--Under-glaze (applied to colours).

  =Vent.=--A hole to aid the even distribution of fire in a kiln or
    to accelerate the cooling off.

  =Waster.=--Commercially, a spoiled pot; defective ones are termed
    “seconds.”

  =Wedging.=--The beating or slamming operation usually employed to
    expel air or correct inequalities just before clay is used by
    the thrower.

  =Whirler.=--A circular support pivoting on its centre, used in
    casting or banding; similar to a banding wheel, but usually
    heavier.


                         MATERIALS, TERMS, ETC.

  C = COMBINING WEIGHT
  E = EQUIVALENT WEIGHT
  ------------------------------------------------+------+--------------
                                 SYMBOL           |C OR E| FUSING POINT
  ------------------------------------------------+------+--------------
  Alumina (calcined)            Al_{2}O_{3}       |C 102}|Very infusible
  Alumina (hydrated)        Al_{2}O_{3}·3H_{2}O   |C 156}|
  Aluminium                        Al             |E 27  |627° C.
  Ammonia                         NH_{3}          |      |Volatile
  Antimony                         Sb             |E 120 |432° C.
  Antimony oxide                   SbO            |      |
  Arsenic                          As             |E 75  |500° C.
  Barium (metallic                 Ba             |E 137 |Fuses above
    element)                                      |      |  red heat
  Barium carbonate               BaCO_{3}         |C 197 |
  Barytes                        BaSO_{4}         |C 233 |Fuses about
                                                  |      |  white heat
  Bauxite                                         |      |
  Bismuth                          Bi             |E 28  |
  Borax (crystals)     Na_{2}B_{4}O_{7}·10H_{2}O  |C 382 |Very fusible
  Boric acid (crystals)       B_2O_3·3H_2O        |C 124 |
  Boric acid (dry)               B_2O_{3}         |C 70  |High fusing
  Boron (metallic                  B              |E 11  |  point
    element)                                      |      |
  Calcined bones                                  |      |Infusible
  Calcined kaolin}           Al_2O_3 · 2SiO_{2}   |C 222 |Very infusible
  China clay (fine)}                              |      |  slightly
                                                  |      |  vitreous
                                                  |      |  at highest
                                                  |      |  fire
  Calcium oxide (lime)             CaO            |C 56  |Very refractory
                                                  |      |  if alone
                                                  |      |  but fusible
                                                  |      |  with clays
  Calcium carbonate              CaCO_{3}         |C 100 |
  China stone}        8SiO_{2}·2Al_{2}O_{3}·K_{2}O| 1379 |1300° C. about
  Cornish stone}                                  |      |
  Chrome oxide                 Cr_{2}O_{3}        |C 79  |
  Chromium                         Ca             |E 51  |Above platinum
  Cobalt                           Co             |E 59  |1500° C.
  Cobalt oxide                 Co_{2}O_{3}        |C 165 |
  Cobalt oxide (black)         Co_{2}O_{4}        |C 240 |
  Copper                           Cu             |E 63  |1054°-1084° C.
  Copper oxide (black)             CuO            |C 79.5|
  Earthy colourants                               |      |
    Ochres                                        |      |
    Siennas                                       |      |
    Umbers                                        |      |
  Felspar             6SiO_{2}·Al_{2}O_{3}·K_{2}O |C 556 |1200°-1300° C.
                                                  |      |  about,
                                                  |      |  according
                                                  |      |  to purity
  Flint (calcined)               SiO_{2}          |C 60  |1830° C. about
  Fluorspar                      CaF_{2}          |      |Much lower
                                                  |      |  than felspar
  Galena (lead sulphide)          PbS             |      |Very fusible
  Gold                             Au             |E 147 |1054°-1075° C.
  Gypsum  (plaster of                             |      |
    Paris, if calcined)     CaSO_{4}·2H_{2}O      |C 172 |
  Iron                             Fe             |E 56  |1530°-1600° C.
                                                  |      |  about
  Iron oxide                   Fe_{2}O_{3}        |C 160 |
  Iridium                          Ir             |E 193 |1950° C. about
  Kaolin (see calcined                            |      |
    kaolin)           Al_{2}O_{3}·2SiO_{2}·2H_{2}O|C 258 |Infusible
  Lead (metal)                     Pb             |E 206 |326° C.
  Lead carbonate                 PbCO_{2}         |      |
  Lead, red oxide of           Pb_{3}CO_{4}       |      |
  Lime (see calcium oxide                         |      |
    or carbonate)                  CaO            |      |
  Lynn sand (see silver                           |      |
    sand)                        SiO_{2}          |      |
  Magnesia (calcined)              MgO            |C 40  |430° C.
  Magnesia (carbonate)          MgO·CO_{2}        |      |
  Manganese, carbonate           MnCO_{3}         |C 115 |
  Manganese (metal)                Mn             |E 55  |1670° C. about
  Manganese oxide (or                             |      |
    black)                       MnO_{2}          |C 87  |
  Nickel (metal)                   Ni             |E 58  |1427°-1450° C.
  Nickel oxide                     NiO            |C 75  |
  Nitre                          KNO_{3}          |      |
  Pearl ash or potash              KOH            |      |
  Plaster of Paris                                |      |
    (calcined gypsum)      CaSO_{4}·1/2H_{2}O     |C 145 |
  Platinum                         Pt             |E 197 |1710°-1775° C.
  Potash, bichromate of      K_{2}Cr_{2}O_{7}     |      |Fuses dull-red
                                                  |      |  heat
  Potassium carbonate          K_{2}CO_{3}        |C 138 |
  Potassium oxide                K_{2}O           |C 94  |
  Quartz}                        SiO_{2}          |C 60  |1830° C. about
  Quartz sand}                                    |      |
  Rutile (see titanium)                           |      |
  Salt                            NaCl            |      |776° C.
  Silica                         SiO_{2}          |C 60  |
  Silver sand (or quartz                          |      |
    sand)                        SiO_{2}          |      |
  Silver (metal)                   Ag             |E 107 |945°-962° C.
  Soda ash (calcined)          Na_{2}CO_{3}       |C 106 |
  Soda crystals          Na_{2}CO_{3}·10 H_{2}O   |C 286 |
  Sodium oxide                   Na_{2}O          |C 62  |
  Tincal (see borax)                              |      |
  Tin (metal)                      Sn             |E 119 |233° C.
  Tin oxide (white)              SnO_{2}          |C 150 |
  Titanium oxide (rutile)        TiO_{2}          |      |Infusible
  Uranium (metal)                  U              |E 239 |1800° C. about
  Uranium, oxide of            U_{3}O_{8}         |      |
  Whitening (see lime                             |      |
  carbonate)                                      |      |
  Zinc (metal)                     Zn             |E 65  |443° C.
  Zinc oxide (white)               ZnO            |C 81  |
  ------------------------------------------------+------+--------------


            SEGER CONES. (STANDARD CONES. ABOUT 10° HIGHER.)

                 NUMBERS. TURNING POINTS. COLOUR, ETC.

                                 APPROXIMATE
                                  DEGREES OF
  COLOUR IN KILN         CONE    HEAT AT WHICH   MATERIALS SUITABLE TO BE
                        NUMBER    CONE TURNS   FIRED AT THESE TEMPERATURES
                                   OR BENDS          (APPROXIMATE)

                                 _Centigrade_

                         .022        600°
  Commences to           .021        650°     Soft  enamel or over-glaze
  show colour            .020        670°       colours.
                         .019        690°
                         .018        710°
  Dull red               .017        730°     Enamels on metals. Fluxes
                         .016        750°       and lustres.
                         .015        790°
                         .014        815°
                         .013        835°     Very soft glazes and hard
  Red to cherry          .012        855°       enamel colours. Some
                         .011        880°       lustres. Gilding.
                         .010        900°
                          .09        920°
                          .08        940°
                          .07        960°
  Dull cherry to          .06        980°     Majolica glazes or coloured
  light cherry            .05       1000°       glazes and stanniferous
                          .04       1020°       or tin glazes.
                          .03       1040°
                          .02       1060°     Earthenware glazes. Soft
                          .01       1080°       China glazes.
                            1       1100°
  Dark orange to            2       1120°     Soft to hard or fine
  pale orange               3       1140°       earthenware biscuit.
                            4       1160°
                            5       1180°     Sèvres soft bisque.
                            6       1200°
                            7       1230°     Vitreous ware. Granite ware.
  Yellowish white           8       1250°     Salt glaze. Stoneware.
                            9       1280°     English bone porcelain or
                           10       1300°       China biscuit.
  White                    11       1320°
                           12       1350°
  Intense white            13       1380°     German & Chinese porcelain.
                           14       1410°     Sèvres porcelain.
                           15       1430°
  Bluish white            {16}      1460°
                          {17}      1480°     Copenhagen porcelain.

To convert temperatures:

Centigrade into Fahrenheit.--Divide by 5, multiply by 9, and add 32.

Fahrenheit into Centigrade.--Subtract 32, divide by 9, and multiply by 5.


                        MEASURES, WEIGHTS, ETC.

                              APOTHECARIES

                1 grain   = .0648 gramme.
  20 grains   = 1 scruple = 1.296 grammes.
   3 scruples = 1 drachm  = 3.888 grammes.
   8 drachms  = 1 ounce   = 31.103 grammes.

                                  TROY

                    1 grain       = .0648 gramme.
        24 grains = 1 pennyweight = 1.555 grammes.
  20 pennyweights = 1 troy ounce  = 31.1035 grammes.

                              AVOIRDUPOIS

          16 drams = 1 ounce.
         16 ounces = 1 pound.
         14 pounds = 1 stone.
         28 pounds = 1 quarter.
        112 pounds = 1 hundredweight (cwt.).
  20 hundredweight = 1 ton (2240 lbs.).


                             CAPACITY (WET)

              1 gill   = 1.42  decilitres.
    4 gills = 1 pint   = .568  litre.
    2 pints = 1 quart  = 1.136 litres.
   4 quarts = 1 gallon = 4.545 litres.
  2 gallons = 1 peck   = 9.09  litres.
    4 pecks = 1 bushel.
  8 bushels = 1 quarter.


                           BOOKS OF REFERENCE

  TECHNICAL
    Chemistry of Pottery. Langenbeck, Karl.
    Chemistry of Pottery. Shaw, Dr. S.
    Clays. Occurrences, Properties, and Uses. Ries.
    Colouring and Decorating of Ceramic Ware. Brongniart, A.
    Ceramic Technology. Binns, C. F.
    Notes on the Manufacture of Earthen Ware. Sandeman, E. A.
    Notes on Pottery Clays. Fairie, Jas.
    Pottery Decoration. Hainbach, R.

  TECHNICAL AND HISTORICAL
    Leadless Decorative Tiles. Furnival, W. J.
    Faience and Mosaic, and other volumes. Furnival, W. J.

  MANUAL
    Pottery. Lunn, Richard.
    Grand Feu Ceramics. D’oat, Taxile.
    The Potter’s Craft. Binns, C. F.
    Practical Keramics for Students. Janvier, C. A.

  HISTORICAL AND ARTISTIC
    Art of the Old English Potter. Solon, L. V.
    Chinese Porcelain. Gulland.
    Chinese Porcelain. Monkhouse, Cosmo.
    Ceramic Art in Great Britain. Jewitt, L.
    History of Pottery and Porcelain. Marryat.
    Majolica. Fortnum, C. D. E.
    Potters, Their Arts and Crafts. Sparkes and Gandy.
    Pottery and Porcelain in the United States (and other volumes).
      Barber.
    Persian Ceramic Art (and other volumes). Wallis, H.
    Illustrated catalogue of the Faience of Persia and Near East.
      Burlington Fine Arts Club.


                     APPLIANCES AND MATERIALS, ETC.

                                         SOLD BY

  BALL MILLS.                   Wengers, Ltd. Eng. (Hanley, Stoke
                                  on Trent.)

                                Abbey Engineering Co. 220 Broadway,
                                  N. Y. City, U. S. A.

  BISCUIT SHAPES.               Hirshberg Art Co. Baltimore, Md.

        {CHINA AND BALL.        Mandle and Sant.  East Liverpool,
                                  Ohio, U. S. A.

        {CHINA AND MODELING.    Stewart & Co. N. Y. City, U. S. A.

  CLAYS {                       Wengers. Hanley, Great Britain.

        {MODELLING AND          Western Stoneware Co. Monmouth,
        {STONEWARE                Ill., U. S. A.

        {SAGGAR AND STONEWARE.  W. H. Cutter, Woodbridge, N. J.,
                                  U. S. A.

  CONES.                        Wengers, Ltd. Hanley, Eng.

                                Drackenfeld & Co. Murray St., N. Y.
                                  City, U. S. A.

                                Professor Ed. Orton. Columbus, Ohio.

  GLAZES.                       Wengers, Ltd. Hanley, Eng.

                                Drackenfeld & Co. Murray St., N. Y.
                                  City, U. S. A.

                                Roessler, Haslacher Chemical Co.
                                  William St., N. Y. City, U. S. A.

  KILNS. GAS.                   Fletcher, Russell. Warrington, Eng.

  KILNS. GAS AND OIL.           Bellevue Perfection. Detroit, Mich.,
                                  U. S. A.

  KILNS. OIL.                   Caulkins Revelation. Detroit, Mich.,
                                  U. S. A.

  KILNS. TRIAL.                 Wengers. Hanley, Eng.

  LAWNS AND SIEVES.             Drackenfeld & Co. 50 Murray St.,
                                  N. Y. City.

                                A. Sartorious & Co. Murray St., N. Y.
                                  City.

                                Wengers. Hanley Staffs, Eng.

  PLASTER.                      Wengers. Hanley, Eng.

                                Drackenfeld & Co. N. Y. City.

                                Calvin Thompkins. Battery Pl., N. Y.
                                  City.

  QUARTZ, FLINT, FELSPAR.       Wengers, Ltd. Hanley, Eng.

                                Drackenfeld & Co. Murray St., N. Y.
                                  City, U. S. A.

                                Golding & Sons. Trenton, N. J.,
                                  U. S. A.

  SCALES.                       Wengers. Hanley Staffs, Eng.

                                Hy. Troemner. Philadelphia, Pa.,
                                  U. S. A.

  STILTS, ETC.                  Trenton Stilt & Spur Co. Trenton,
                                  N. J., U. S. A.

                                Wengers. Hanley, Eng.

  U. G. COLOURS, ETC.           Wengers. Eng.

                                Drackenfeld & Co. N. Y. City, U. S. A.

  WHEELS.                       Crossley Mfg. Co. Trenton, N. J.,
                                  U. S. A.

                                T. S. Nickerson. Newburyport, Mass.,
                                  U. S. A.

       *       *       *       *       *


                        TRANSCRIBER’S AMENDMENTS

Transcriber’s Note: Blank pages have been deleted. On pages that remain,
some unnecessary page numbers may have been deleted when they fall in the
middle of lists. Some illustrations may have been moved. When the author’s
preference can be determined, we have rendered consistent on a
per-word-pair basis the hyphenation or spacing of such pairs when repeated
in the same grammatical context. The publisher’s inadvertent omissions of
important punctuation have been corrected.

The following list indicates any additional changes. The page number
represents that of the original publication and applies in this etext
except for illustrations since they may have been moved.

  Page          Change

   20  the highest fire (around 17000°[1700°] Centigrade).
   91  but it is [a] waste of time to attempt it
  181  The slip is allowed to settled[settle] and the water siphoned off.
  193  AL[Al]_2O_3 · 2SiO_{2}
  193  Cobalt                 |             C_{6}[Co]
  194  Felspar                |6SiO_{2}·Al_{2}O_{3}·K^{2}O[K_{2}O]

       *       *       *       *       *





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