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Title: How to Enamel - Being a Treatise on the Practical Enameling of Jewelry with Hard Enamels
Author: Chapin, Howard M.
Language: English
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*** Start of this LibraryBlog Digital Book "How to Enamel - Being a Treatise on the Practical Enameling of Jewelry with Hard Enamels" ***
HOW TO ENAMEL
BEING A TREATISE ON THE
PRACTICAL ENAMELING OF JEWELRY
WITH HARD ENAMELS
BY
HOWARD M. CHAPIN
AUTHOR OF “LIFE OF DEA. SAMUEL CHAPIN,” ETC.
_FIRST EDITION_
FIRST THOUSAND
NEW YORK
JOHN WILEY & SONS
LONDON: CHAPMAN & HALL, LIMITED
1911
------------------------------------------------------------------------
COPYRIGHT, 1911
BY
HOWARD M. CHAPIN
Stanhope Press
F. H. GILSON COMPANY
BOSTON, U.S.A.
------------------------------------------------------------------------
CONTENTS
PAGE
LIST OF ILLUSTRATIONS v
PREFACE vii
INTRODUCTION ix
CHAPTER I
PREPARATION OF THE ENAMEL 1
CHAPTER II
PREPARATION OF THE METALS 8
CHAPTER III
CHARGING 14
CHAPTER IV
FIRING 23
CHAPTER V
STONING 29
CHAPTER VI
POLISHING 37
CHAPTER VII
FOILS—PAILLONS—GLITTER ENAMEL—DULL 42
FINISH—PLIQUE-À-JOUR
CHAPTER VIII
ENAMEL PAINTING 50
CHAPTER IX
PHOTOGRAPHS ON ENAMEL 57
------------------------------------------------------------------------
LIST OF ILLUSTRATIONS
FIG. PAGE
1 AGATE MORTAR AND PESTLE x
2 GRINDING WITH WEIGHTED PESTLE 2
3 ENAMELER’S SPATULA WITH WOODEN 10
HANDLE
4 CHARGING 14
5 METAL TRAY AND TILE 24
6 FIRING 30
7 CARBORUNDUM OR EMERY STONE 37
8 STONING 44
9 PICKLE PAN 51
10 POLISHING 58
11 PICKLE POT 65
------------------------------------------------------------------------
PREFACE
The aim of this book is to explain practical enameling in such a way
that one entirely unacquainted with the subject will, after a little
study, not only understand the fundamental principles of the art, but
with a little practice be able actually to achieve creditable results in
this most fascinating branch of the jeweler’s craft.
------------------------------------------------------------------------
INTRODUCTION
Enamel is really a glaze applied to metals just as other glazes are
applied to porcelain, glass, and earthenware. We will confine our
attention to what is known as hard enamel in contradistinction to
japans, lacquers, and enamel paints, which are often called soft
enamels. Hard enamels are compounds of glass with different metallic
oxides which produce the different colors. These compounds are fused
together at a very high temperature and on cooling become extremely
hard. They fill the gap between glass and china, the transparent
fondants being to the layman indistinguishable from glass, while the
opaque whites may be easily mistaken for china, and the countless other
varieties form a chain of scarcely perceptible gradations from one
extreme to the other.
[Illustration:
FIG. 1. AGATE MORTAR AND PESTLE.
]
The use of enamels is both very ancient and very widespread, for we find
the process known to the ancient Egyptians and to the Chinese, although
the highest development in the art was reached in France in the
sixteenth century. We would refer the historical student to Cunynghame’s
“European Enamels” in English and Luthmer’s “Enamel” in German.
Jewelry enameling is usually divided into five different classes, viz:
champlevé, cloisonné, incrusted, plique-à-jour, and enamel painting.
Champlevé enamel is that in which a part of the metal is cut away,
leaving a depression which is filled with enamel to the level of the
surface of the metal, thus giving a sort of inlaid effect. If the enamel
surface is not filed off flat but allowed to have a concave or convex
surface the piece is said to be “flushed.” Technically enamel is
“flushed” if it is not “stoned.” When transparent enamels are used and
the background under the enamel is cut in relief, it is called
“Baisse-taille enamel.”
Cloisonné enamel is hardly distinguishable from champlevé when finished,
but is made differently. Instead of cutting depressions in the metal to
hold the enamel, metal wires are soldered on the smooth surface of the
metal, thus forming partitions or fences between which the enamel is
placed.
Incrusted enamel is that in which the enamel is charged directly on the
metal surface without any raised metal edges to hold it. It is generally
used in small daubs or beads to reproduce the effect of precious stones.
Plique-à-jour enamel is similar to cloisonné except that the wires are
soldered to each other without any background, thus forming a sort of
filigree, the spaces within which, when filled with enamel, somewhat
resemble a stained-glass window.
In enamel painting a picture is painted on the enamel. Usually white
opaque enamel is used for the background, and the painting is executed
with finely ground enamel or china paints, after which it is covered
with a layer of transparent enamel which serves as a protection for the
painting.
------------------------------------------------------------------------
CHAPTER I
PREPARATION OF THE ENAMELS
ENAMEL is generally bought in the form of hard chunks more or less flat
and varying from the size of an acorn to that of a large dinner plate.
When it is made it is poured into a mold where it hardens in the form of
a disk or slab generally a foot or more in diameter, and later gets
broken into smaller pieces during transportation.
These chunks of enamel may be readily broken up by a hammer, and if they
are first wrapped in a piece of cloth the small particles will not fly
about and get into one’s eye, and no enamel will be lost. When the
enamel has been broken up so that none of the pieces are larger than a
pea, it should be washed in clean water to free it from any dirt that it
naturally contained or that it received from the cloth in which it was
wrapped during the hammering process.
Cleanliness cannot be too much emphasized, for the slightest particle of
dirt mixed in with the enamel may often completely spoil a piece of
work.
Enamel if heated quite hot and then plunged into cold water will become
so brittle that it can be broken up by the hands, but when treated in
this manner is said to be harder to grind.
[Illustration:
FIG. 2. GRINDING WITH WEIGHTED PESTLE.
]
After the enamel has been broken up into small pieces it should be put
in an agate or porcelain mortar and ground to a fine powder. This will
take from twenty to twenty-five minutes of steady grinding, the length
of time depending on the quality and quantity of the enamel, the
strength used, etc. Water may or may not be mixed with the enamel during
the grinding process, as the grinder prefers. If water is added the
process may take a little longer but a very disagreeable noise is
eliminated and the work may perhaps be slightly easier. Agate mortars
are cleaner and so better than porcelain ones but are so much more
expensive that they cannot be used for grinding large amounts. For this
grinding machines or weighted pestles, such as Cunynghame describes in
his “Art Enameling upon Metals,” should be used. The enamel should be
ground until it is about the size of fine sand, and soft, not gritty,
when rubbed gently between one’s thumb and forefinger. It should now be
rinsed in clean (the purer the better) running water, the enamel being
thoroughly stirred up and washed, the fine particles, “dregs” or
“slimes” as they are called, being allowed to flow away. Often from ten
to thirty per cent of the enamel is lost in this process. The remaining
wet enamel powder is ready to be used. It may be kept for weeks under
water in a glass jar or druggist’s salve box, but in time is said to
deteriorate. If the enamel is to be used immediately it may be placed
upon a clean copper or china palette which will be found very
serviceable. It should be kept constantly wet and if possible under
water. If, however, it becomes dry, it may be washed as described above
and will probably be found in good condition; if not a slight grinding
may assist matters.
If enamel is not ground fine enough it is apt to have pit-holes in it
when fired, and if it is not absolutely clean it is likely to have both
pit-holes and black spots in it. Sometimes enamel is washed in nitric
acid as well as water but this is generally not necessary. It is very
important, however, to use water that contains very little iron, for
iron will cause black spots in the enamel.
If enamel is to be kept for any length of time it should be kept either
as chunks preferably or as coarsely ground powder. When coarsely ground
it may be kept dry in a dirt-proof jar or bottle.
The “dregs” and “slimes” if washed clean may be kept and used for paints
in painting on enamel.
When enamel is bought in the form of a powder it is generally necessary
to grind it finer and wash it thoroughly.
------------------------------------------------------------------------
CHAPTER II
PREPARATION OF THE METALS
MANY metals can be enameled, but the most practical ones, those most
used in jewelry, are gold, silver, copper, and their alloys. Hence we
will confine our descriptions to these metals.
Whatever metal is used, however, must first be made chemically clean
before it is “charged” or covered with enamel. This may be done in a
number of different ways, of which the following is considered the most
practical.
The metal, whether gold, silver, or copper, must be annealed by being
heated to a red heat and allowed to cool slowly in the air. When cool it
will be found to be covered with a black oxide.
The metal must now be plunged for half a minute or more into a solution
called a “dip,” consisting of two parts sulphuric acid (H_{2}SO_{4}),
two parts nitric acid (HNO_{3}), and a slight touch of hydrochloric acid
(HCl); a few drops of the latter to the gallon will suffice. This dip
will clean the surface of the metal and make it bright. As the solution
gets old it will become weak and a longer dip will be required. The
ordinary commercial acids are suitable for making these dips. Care
should be taken not to inhale the fumes of the acids, as they are quite
poisonous.
This dip may be used cold, but better results are obtained when it is
heated to 170°F. A convenient way to heat it is to set the jar
containing the dip in a larger jar containing water and then to heat the
water in the larger jar.
Many prefer to use first a hot and then a cold dip, rinsing the metal in
clean water between the dips. Experience will soon teach one to tell
when the metal is clean by looking at it, and this in fact is the only
satisfactory way, as the length of time required will vary with the
condition of the metals and the strength of the dip.
[Illustration:
FIG. 3. ENAMELER’S SPATULA WITH WOODEN HANDLE.
]
After the dip the metal must be thoroughly rinsed in clean water and
then dried in clean sawdust or hot air. If rinsed in very hot water the
metal will dry itself almost immediately. Some prefer to rinse the metal
in ammonia as well as in water in order to rid it of all trace of the
acid, but this is not generally necessary. If the metal is copper or
gold it is now ready to be charged, but if it is silver it must be
“fire-stained.”
There are many other possible ways of cleaning metals, but the above
means are generally used and will doubtless be found the most
convenient. If small quantities only are being “cleaned,” a copper
pickle pan and a Bunsen gas burner will suffice, while for large
quantities earthen pickle pots and large jars will be found
advantageous. Metals if “wriggled,” that is, scraped or engraved all
over with a graver, are generally clean enough to be charged.
If silver is used it must be “fire-stained,” or have the “fire” taken
out of it. This is done in the following manner. The silver is submerged
for a minute or more in a solution of four parts nitric acid and one
part water, heated to 170°F. The acid will react on the silver, which
will become covered with a brownish scum. The silver should now be
rinsed in clean water and brushed with a metal brush in a solution of
soap-tree bark and water. This will clean the scum off the silver and
make the latter bright. After being rinsed in clean water, the silver is
ready to be charged with enamel. Sour beer, or a solution of licorice
root and water may be used instead of soap-tree bark. It will be very
convenient to have the metal wire brush a circular one revolving on a
lathe.
If red enamel is to be used, the metal should always be either wriggled
or engine turned or else have some design cut sharply in it, in order to
bring out the brilliancy of the color. Engine turning and sharp
engraving or relief in the metal background will always enhance the
brilliancy and give an additional sheen to any transparent colors. As
the depth of the enamel layer has a great deal to do with the shade of
the enamel, different effects can be obtained, even when only one enamel
is used, if the metal background has been cut lower in some places than
in others.
If the silver is not “fire-stained,” red enamel will often become maroon
when fired, and fondant and other delicate colors will become streaked
or spotted. If the fire-staining and dipping have not been carefully
done, the enamel is likely to chip out, have pit-holes in it, or contain
black blotches.
As the acid fumes eat the flesh quite rapidly, it is advisable to wear
rubber gloves when dipping the metals.
------------------------------------------------------------------------
CHAPTER III
CHARGING
ENAMEL is “charged,” or put on the metal, in the form of a watery mud,
by means of a small spatula. The most convenient spatula is one made
from a piece of steel wire about the size of a crochet needle and
flattened at one end. In fact a crochet needle itself, flattened at one
end, or even the small blade of a penknife, will be found quite
serviceable. If this spatula is mounted in a wooden handle made from a
penholder it will be found very easy to handle.
[Illustration:
FIG. 4. CHARGING.
]
A small daub of very watery enamel should be taken on the end of the
spatula and laid upon the metal where it is to be enameled. If the
surface to be enameled is very large, a larger spatula can be used to
advantage. If the enamel is too watery it will not stick to the spatula
while being taken from the palette, and if it is too dry it cannot be
readily transferred from the spatula to the metal.
When the piece has been entirely covered with enamel, it should be held
in the hand and tapped gently with the spatula. If the enamel is wet
enough this procedure will spread it evenly over the metal. The water
should now be drawn off from the enamel by means of a clean piece of
cloth or blotting paper. The remaining moisture will soon evaporate,
leaving the enamel perfectly dry. Only when perfectly dry is it in a
condition to be fired.
Care must be taken not to get the enamel on too thick, as in that case
it will chip off when fired. On the other hand, enamel shrinks
considerably on being fired, so if it is put on too thin it is apt to
shrink, leaving bare spaces of metal. The proper thickness with which to
charge a piece of work can only be learned by experiment, and in most
cases it is desirable to charge a piece with several thin coats rather
than with one thick one.
In cloisonné and champlevé work it is generally necessary to use at
least two coats in order to bring the enamel up to the level of the
metal parts. Originally in these kinds of enameling the idea was to have
each color or shade of enamel separated by a metal wall from every other
shade, which made the charging comparatively simple. Now the vulgar
modern taste permits several different shades side by side without
partitions, or even blended. If the enamel is not too wet two distinct
colors can be charged side by side without having them run into each
other to any appreciable extent. They may then be fired, and they will
be no more mixed in that process than they were before it.
A blend between two colors may be obtained by mixing two enamels
together and then charging the piece with the mixture. Such a mixture
when fired is often found to be speckled instead of a clear shade. If,
after mixing, the enamel is ground finer, this speckled effect can
sometimes be eliminated. This process is by no means always
satisfactory.
Another way that two colors can be blended is as follows: Divide a piece
to be enameled into three parts by two imaginary lines and call the
parts _A_, _B_, and _C_. Now charge _A_ and _B_ with a thin coat of, for
instance, blue, and _C_ with a thin coat of red, and fire the piece.
Then on the second charging charge _A_ with blue and _B_ and _C_ with
red. When fired, part _B_ will be found intermediate between _A_ and
_C_, in this case a sort of purple. This purple may be made bluish or
reddish, as desired, by using a preponderance of blue or of red enamel.
This preponderance can be largely regulated by the thickness of the
layers or coats of each color, although the last coat, other things
being equal, will, on account of its position, exert by far the stronger
influence.
With most transparent colors it is desirable, though not necessary
except in the case of so-called “opals,” to use an under layer of
fondant, that is, on the first charging, to cover the entire surface
with a thin layer of transparent white or colorless enamel, commonly
called flux or fondant. This under layer of fondant is used more on gold
than on silver or copper, but in any case it will greatly enhance the
brilliancy of the enamels. It is of great assistance in bringing out
delicate colors and especially “opals,” for if opals are charged
directly upon the stock they have a strong tendency to become opaque
when fired. Some delicate roses and pinks if put directly upon the metal
will “fire” black, while over a layer of fondant they became beautiful
and delicate shades.
Where several colors are used on the same piece it is generally
advantageous to use fondant for the last layer. The advantage of this is
that the harmony and qualities of the different colors are then not
affected by the stoning and polishing, which no matter how carefully
done are bound to cut down the enamel, and in the case of transparent
colors the thinner a layer becomes the lighter it becomes.
Any transparent color can be made lighter either by being stoned down or
by being put on over a layer of fondant. Transparent white can easily be
obtained on silver by the use of bluish and white fondants, but it is
impossible to obtain transparent white on gold or copper unless these
metals are first plated with silver.
Most enamels appear to best advantage on silver over fondant, and when
the same enamel is put on another metal it changes its hue. This change
of hue varies with each individual enamel and can only be learned by
experiment. In general, white (fondant) on silver becomes pink on gold
or copper, orange becomes red, yellow becomes orange or brown, blue has
a tendency to green and green to yellow. Opaque colors of course do not
actually change color, but owing to the different color of their setting
they often give different effects.
Some shades that cannot be obtained by mechanically mixing opaque colors
or by layers of different transparent colors, can be obtained by putting
a layer of transparent enamel over a layer of opaque. Opaque white as an
under layer will often give a desirable shade to a transparent enamel
which is not just the color required.
------------------------------------------------------------------------
CHAPTER IV
FIRING
AFTER enamel has been charged on a piece of metal, it is “fired,” that
is, heated until the enamel is fused, after which, on cooling, it
becomes hard. It is best fired in a muffle furnace, although with care a
nice job may be done with a blowpipe, a Bunsen burner, or even an
alcohol lamp.
In case a Bunsen burner or lamp is used, it is well to have a metal
tripod supporting a sheet of metal or wire mesh on which to set the
work, as holding it by a pair of tongs becomes very tedious.
[Illustration:
FIG. 5. METAL TRAY OR TILE.
]
A muffle may be heated by electricity, gas (with or without an air
blast), oil, coal, or wood. Electricity or gas, however, is preferable,
as they are not accompanied by dirt. The muffle itself, which is simply
a small oven, is generally made of fire clay, although both fused quartz
and nickel are sometimes used. A door to the muffle is not necessary,
although it is an aid to cleanliness. If, however, a door is used it
should have a hole in it large enough to allow the enameler to watch his
work constantly. It is very important to keep the enamel work away from
the oxidizing effect of the fire; so that any cracks that appear in a
muffle must be immediately repaired. It will be found very advantageous,
too, to have the doors of the furnace on the side of it opposite to that
containing the mouth of the muffle.
The pieces to be fired should be laid upon a tray of a size convenient
to pass easily through the mouth of the muffle. These trays are made
preferably of sheet nickel for this metal will not scale or flake off
when heated and so contaminate the enamel. As these trays become quite
hot it is advisable to handle them by means of a pair of long-handled
tongs.
Before placing a tray of pieces in the muffle to be fired, it is well to
leave it near the mouth of the muffle for a minute or two so that the
enamel may become entirely dry before it is placed in the muffle, for if
damp the enamel will be blown off of the metal by the rapid evaporation
of the water which it contains.
When the pieces are fully dry, the tray may be placed in the muffle,
which should be heated to a bright red heat of about 1400° F. With such
a heat it should take from half a minute to two minutes to “fire” or
melt the enamel. The time required will vary with different enamels and
can only be learned by experiment. The enamel should be kept in the
muffle until it begins to melt and its surface becomes fused and
comparatively smooth and glossy, when it should be removed from the
furnace and allowed to cool in the air. It is not necessary or even
desirable to fire the enamel perfectly smooth in the first firing. It
generally takes at least two coats, that is two chargings and two
firings, before a piece is ready to be stoned. If, however, only one
coat is to be used, it should be fired as smooth as possible.
When the pieces cool, the metal (unless it is fine, _i.e._, pure,
unalloyed) will be found covered with a black scale caused by oxidation.
This may be removed by simply brushing it, which operation in most cases
will clean the piece sufficiently for the second charging. Otherwise the
piece may be “pickled,” or cleaned with acid.
Subsequent firings do not differ from the first one except that in the
last firing the enameler should try to obtain as smooth a surface as
possible.
After the last firing the pieces should be submerged for a minute or two
in a mild pickle consisting of one part sulphuric acid and one part
water. This will clean off the oxide and make the metal bright.
If red enamel is used it is best to throw the piece into a cup of thick
heavy machine oil to cool instead of letting it cool in the air. This
will give the red a greater brilliancy. Red enamel, too, often requires
a greater heat than other colors, although too low a heat tends to
destroy the gloss on any enamel. Many delicate colors which are opaque
when fired at a low heat, will become opalescent and in some cases
transparent if fired at a higher temperature. Red enamel loses its color
if fired too many times, and a large number of firings have a weakening
effect on high-karat gold.
------------------------------------------------------------------------
CHAPTER V
STONING
AFTER a piece of enamel has been fired, it is often found that too much
enamel has been used, that is, that the enamel may have run over the
edge of the part to be enameled, or it may not present a smooth surface
but instead consist of a series of humps, or, especially in the case of
transparent enamels, it may be on in such layers that the color is
deepened or even lost entirely.
This can be remedied by what is known as “stoning,” or filing the enamel
down to a smooth surface. In the case of work that is to be polished it
is always considered best to overcharge the piece and then file it
smooth rather than to try to “flush” it evenly.
Stoning is usually done by means of emery “stones” or “sticks,” which
are made by mixing powdered emery with shellac and heating the same
until the mixture coheres, when it may be pressed into any shape desired
by means of a flat piece of steel. On cooling the stones become very
hard. They are generally from six to twelve inches long and from
three-eighths to one inch square, tapering at both ends to a rather
blunt point. When a stone wears out or loses its shape it can be
remelted and remodeled. The emery used in these sticks runs from No. 70
to No. 180 grit.
[Illustration:
FIG. 6. FIRING.
]
Carborundum stones are often used in place of emery stones. They are
rather more expensive than emery stones and wear out quicker, but they
cut the work down much faster. No. 120 and No. 180 grits are the most
satisfactory. These stones sometimes get filled up with metal, but in
this case the metal can be eaten out with acid.
It is convenient when stoning to hold the piece to be stoned on a small
block of wood, on which a mold of shellac has been made into which mold
the piece of work will snugly fit. If the block is then set on a pivot
either on a bench or bench-pin, so that it will turn easily, it will
then be found that the stoning process has been made considerably
easier. A piece of hard felt or leather or just a plain piece of wood
will, however, answer the purpose. The idea is simply to hold the piece
firmly and conveniently.
The stone should now be rubbed back and forth across the enamel as a
file is used. It is necessary when stoning to keep both the stone and
the piece to be stoned quite wet. A bowl full of water kept near by will
be found very convenient for the purpose. Care must be taken not to make
any deep scratches on the metallic parts of the piece, as these
scratches cannot easily be obliterated.
The stoning should be continued until the surface is smooth or level
with the edges, or until in champlevé and cloisonné enamel the metal
parts all show evenly, or until the desired depths of color are obtained
in the case of transparent enamels. This of course can only be judged by
experience, as the colors will look much brighter when fired again.
When the stoning is finished it will be found that the surface of the
enamel presents a rather dull or dead appearance, which will be removed
by again firing the piece. Before this firing, however, the piece should
be submerged for about a minute or less in hydrofluoric acid and then
brushed in clean water. This may be done with any small stiff-bristled
hand brush. The piece will dry readily in the air, but more quickly if
first dipped in scalding hot water or brought in contact with steam. It
may also be dried in hot air or sawdust. When dry it is ready to be
fired.
Sometimes after stoning, low places or pit-holes are found in the enamel
surface, which may be remedied by re-charging these places with enamel
and then firing the piece.
When only a very small amount of enamel is to be stoned off, or when one
does not want to fire the piece after the stoning, a soft soapstone
called a “Scotch stone” may be used to advantage.
If the piece to be stoned is small it is desirable to have a small
wooden stick the size of a pencil with which to hold the piece steady
and keep it from slipping out of its mold. Of course a mold is not
always necessary, but will often be found very convenient.
A sharp steel tool, such as a three-cornered scraper or a slightly dull
awl, is very useful to clean out pit-holes or to chip enamel off from
places where it is not desired.
When a large number of pieces are to be stoned, it is advantageous to
use an emery or carborundum wheel of No. 90 to No. 120 grit, from two
and one-half to six inches in diameter and from three-eighths to
three-fourths of an inch thick, revolving on a lathe at a low rate of
speed. A stream of water should be kept constantly dropping on the wheel
in order to keep both the wheel and the work wet.
Rubber cots are a great protection to the fingers, which are gradually
worn away by the stones.
------------------------------------------------------------------------
CHAPTER VI
POLISHING
AFTER an enameled piece has been stoned and fired for the last time, it
is often desirable to give the enamel a gloss or polish additional to
that which it naturally receives from the firing.
[Illustration:
FIG. 7. CARBORUNDUM OR EMERY STONE.
]
If the metal used is other than fine gold or fine silver it will be
black or oxidized when taken from the furnace, in which case it should
be “pickled,” that is, submerged for a minute or two, until the
oxidization is removed and the metal becomes bright, in a mild “pickle”
consisting of a warm solution of one part sulphuric acid and one part
water. The piece should now be rinsed in clean water, after which it
will be ready to be polished.
Polishing is best done on a lathe with a swiftly revolving wheel, say
about 2200 revolutions per minute. A wheel of from three to six inches
in diameter, made of hard felt or wood, is very satisfactory. If the
felt is thin it is often necessary to make a wooden back for it in order
to keep it flat.
The piece to be polished should be held on a small piece of leather or
felt so that the hands may not come in contact with the wheel, in which
case the skin and nails would soon be worn away. Rubber finger cots will
serve as an additional protection.
The enamel surface to be polished should first be covered with wet
pumice of about the consistency of mud. Then the pumice-covered surface
should be pressed against the face of the felt or wood wheel, and as
soon as the pumice is removed by the action of the wheel more wet
pumice-mud should be added so that the enamel surface may constantly be
kept covered with wet pumice.
It is best to use the finest ground pumice obtainable, although on rough
jobs a coarse grade may be used. Tutty powder (oxide of zinc) is said to
give even a better polish than fine pumice, and is often used after a
preliminary polish has been given by pumice. A different wheel should be
used for each polishing compound.
The polishing should be kept up until the enamel surface takes on the
desired gloss. This polishing process will cut away the metal quicker
than it does the enamel, so that any slight lines and scratches which
the metal received in the stoning will be removed by the polishing. Care
must be taken not to polish away too much of the metal, or to cut down
and destroy any metal ornaments which may be near the enameled part of
the piece. Felt wheels being more pliable than wood wheels have a
tendency to cut down the metal faster than they cut down the enamel (the
enamel being harder than the metal), while wood wheels tend to cut down
both parts equally. Felt wheels, however, are considered to give a
better and quicker polish.
When the piece is polished sufficiently, it should be rinsed and brushed
off in clean water, which will remove all trace of the pumice. The piece
is now finished as far as the enameling process is concerned, but may,
however, be plated, set with stones, engraved, etc., as may be desired.
If after the piece is polished it is found that there are a number of
small pit-holes in it, in which the pumice sticks even after the
brushing, this may be remedied by digging the pumice out with a scraper
or any sharp instrument. If the hole is small and the enamel transparent
it will scarcely show when clean owing to the refractive power of the
enamel. If, however, the hole is so large and noticeable as to be
objectionable it will have to be re-charged and re-fired. In such a case
it is often possible after the first firing to stone it smooth with a
Scotch stone or by polishing and thus avoid another firing.
------------------------------------------------------------------------
CHAPTER VII
FOILS—PAILLONS—GLITTER ENAMEL—DULL FINISH—PLIQUE-À-JOUR
FOILS and paillons are generally made of fine gold or fine silver leaf.
Silver foils are used on copper and gold work in order to obtain better
enamel effects, for most transparent colors are shown to best advantage
over silver. Gold foils are sometimes used on copper for similar
reasons.
The metal is first charged and fired with a coat of any enamel,
preferably a “hard running” white, that is, one that it takes a
comparatively high temperature to melt. The foil is then stuck to the
enamel by means of gum arabic, tragacanth or, in fact, some kinds of
common mucilage will answer the purpose. As Cunynghame says, “What is
wanted is a good tenacious gum, which disappears as completely as
possible when heated and leaves no carbonaceous residue to spoil the
enamel.” The foil should be cut so that it will exactly fit the enamel
surface, and cover it entirely so that none of the white enamel will
show on the finished piece. If the foil is stamped with some design it
will add greatly to the brilliancy of the enamel afterwards applied, and
if it is pierced with a number of small holes through which the fumes of
the gum can escape, it will stick smoothly to the enamel.
After the foil has been put upon the enamel, the piece should be fired
until the foil adheres strongly and smoothly to the enamel, when it is
ready for the next charging. From this point on the process does not
differ from that employed when charging directly upon the metal. (See
chapter on charging.)
Paillons are simply small bits of foil cut into dainty and artistic
shapes such as stars, fleurs-de-lis, etc. They are applied by means of
gum, as in the case of foils, on the surface of the last or upper layer
of colored enamel, after it has been fired, and the piece is again
fired, making the paillons adhere to the enamel. The piece is then
charged all over with a coat of fondant and fired, after which it is
ready to be stoned and polished, if desired.
[Illustration:
FIG. 8. STONING.
]
Glitter enamel, called by the Germans “flimmer,” is simply ground up
goldstone (Aventurin) mixed with an ordinary enamel in equal proportions
or two parts of goldstone to one of enamel. Some very striking effects
can be produced with this mixture, which should be stoned to bring out
the brilliancy of the goldstone. The best effects are obtained when some
dark opaque enamel is used.
To obtain the so-called dead or dull finish on enameled goods, it is
only necessary to submerge the piece for two or three minutes in a
solution of hydrofluoric acid. This will “etch” the enamel leaving the
surface dull like ground glass. When the piece is etched evenly all
over, it should be removed from the acid and washed and dried. The
etching will only take a few minutes if the acid is strong, and will be
done much more evenly if a mixture of hydrofluoric acid and ammonium
carbonate, known as white acid, is used.
If only part of the surface is to be dulled or etched, the part that is
not to be etched should be covered with shellac, or a mixture of three
parts beeswax and one part Burgundy pitch, and allowed to dry before the
piece is put in the acid. The acid must be kept either in lead or wax
bottles, as it eats glass very rapidly. Its fumes are very dangerous and
destroy human tissues.
If for some reason a piece has been enameled wrong, so that it is
desirable to take the enamel off the metal, this can best be done by
leaving the piece for a few hours in a solution of hydrofluoric acid
which will eat the enamel, so that it can easily be brushed off the
metal, leaving it bright.
Plique-à-jour enamel may be done in several ways. The simplest is to lay
the filigree work upon a piece of mica or fire clay and charge with
enamel, as if the mica or fire clay were the background and the filigree
work the sides of the piece. The process continues the same as in
ordinary enameling, except that just before the last firing the mica or
fire clay should be removed.
Copper or silver foil may be used instead of mica, but in this case the
filigree work must be either of gold or platinum, for the copper or
silver foil can only be removed by being dissolved in nitric acid.
The most difficult way is to mix a little gum arabic or gum tragacanth
with very finely ground enamel and charge a layer on the inner sides of
the wires which make up the filigree work. The gums will hold the enamel
in place after it is dried. When the piece has been fired, another layer
of enamel should be charged and so on, until by degrees the entire space
between the wires has been filled up. This process is tedious and
requires much skill and care, but gives very satisfactory results.
------------------------------------------------------------------------
CHAPTER VIII
ENAMEL PAINTING
ENAMEL painting is usually done on a background of opaque white enamel,
although other opaque colors are sometimes used. The metal must be
prepared in the regular manner, and one or two coats of enamel charged
and fired, the last coat being fired to as perfect smoothness as
possible. Instead of flushing the enamel smooth it is often advisable to
stone and fire it, by which processes a smoother surface is obtained.
After this last firing, the black flakes of metallic oxide which will be
found on the metal should be brushed away, leaving the piece clean and
ready to be painted. It is desirable not to have too thick a layer of
enamel, as in that case it is apt to chip off in some of the later
firings. If, on the other hand, the enamel layer is thin, it is quite
difficult to get it smooth.
[Illustration:
FIG. 9. COPPER PICKLE PAN.
]
Any picture desired may now be painted on the enamel surface, either
with ordinary china paints or finely ground enamel “slimes” mixed with
oil of cloves or oil of lavender. This painting may be done with a small
camel’s-hair brush and when finished should be fired until the enamel
fuses. The piece should be allowed to cool slowly and when cool should
be charged with a coat or two of clear fondant which, after being fired,
may or may not be stoned and polished, as the artist sees fit. If the
painting requires it, it may be touched up and fired several times
before being charged with the fondant, but the fewer times a piece is
fired the less chance there is for accidents which may prove fatal to
the work of art.
If the metal used is very thin, it will be necessary to enamel it on the
back as well as on the front, for a thin piece of metal which is
enameled on one side only will warp out of shape, but if enameled on
both sides will keep its shape perfectly. Of course the enamel on the
back may be of any color and need not be finished carefully, as it is
there for use not ornament.
An enamel painting must be fired with great care. First it must be
warmed by degrees before put into the muffle, so that the oil may have a
chance to evaporate. It should then be placed partly in the muffle and
not put way in and should not be heated to a red heat until the residues
of the oils shall have burnt away. If too hot a muffle is used, or if
the piece is fired too long, the painting will appear blurred and faint.
If the painting appears blistered after firing, it is due to the fact
that the oils used contained too much carbonaceous residue.
The fondant used on an enamel painting should be very finely ground,
much more so than for ordinary work, and the first layer of fondant
should not be fired to smoothness but only until it just begins to flow,
as was the case with the painting itself. The last layer of fondant
should of course be fired as smooth as possible.
* * * * *
If a large number of pieces are to be painted with the same design,
there are a number of mechanical means that can be used to take the
place of free-hand painting. We will outline one of these processes,
which is as follows.
Etch a copper plate with the outline of the design that is to be painted
on the enamel. The etching on the copper plate must be a positive, not a
negative; that is, the design must appear on the plate as it is to
appear on the enamel and not reversed as in ordinary etching. The design
must also be exactly the same size as the one to appear on the enamel.
The lines in the etching should now be filled with finely ground enamel
paints mixed with oil of cloves or some such medium. It is best to use
paint of the color that is to predominate in the picture, although in
some cases it will be found that black will give the best working
outline.
When the lines of the etching are filled with the paint, the plate
should be scraped smooth so that no paint remains on it except in the
etched lines. The plate should now be pressed against a piece of thin,
smooth, sheet rubber, to which the paint will stick in preference to the
copper plate, thus transferring the design to the sheet of rubber, where
it appears reversed.
The rubber with the design side down is now pressed upon the smooth
surface of the white enamel, which should be prepared in the same way as
it would be prepared for regular painting. The design is thus
transferred from the rubber to the enamel surface, where it appears
again positive.
The enamel surface now has on it the outline of the design either in
black or in color as the case may be. From this point on, the process is
the same as in regular hand painting on enamel, but as the outline has
been blocked in, the work is considerably easier. A speed and uniformity
are obtained by this process which it is difficult to equal with
free-hand work.
Another process whereby a number of similar designs can be easily
executed is by decalcomania. Decalcomania pictures are made in Germany
and can be obtained through any artists’ supply house. In this case the
white enamel background is obtained in the usual manner, after which a
decalcomania picture is transferred to the enamel surface. The enamel is
first covered with a very thin layer of size or gum as in the case of
foils. When the size becomes sticky, the decalcomania picture should be
placed face downwards on the enamel. The paper on the back of the
picture should now be wet with a sponge until it becomes loose, when it
should be removed and the remaining scum washed off with plenty of clean
water. The piece after being dried thoroughly is ready to be fired. The
rest of the process is the same as in regular painted enamel work. Great
care must be taken in firing the decalcomania work.
------------------------------------------------------------------------
CHAPTER IX
PHOTOGRAPHS ON ENAMEL
THERE are several methods by which photographs may be reproduced upon
enamel. However, since they are rather difficult, we will explain only
one method, and for the other processes will refer the student to Dr.
Paul Liesegang’s treatise on photographing on enamel, porcelain, and
glass, which is printed in German.
In the first place only the best quality of mirror glass should be used
for the plates, as it is essential that they should be perfectly smooth
and without blemishes. The glass should then be cut the same size as the
negative plate which is to be used later. The glass plate must be made
perfectly clean, which is best done by placing it in a mild sulphuric
acid bath for about ten minutes and then washing it well with clean
water. It should be dried with a clean cloth or tissue paper, after
which it may be wrapped in clean dry tissue paper and kept in a dry
place until needed.
[Illustration:
FIG. 10. POLISHING.
]
Out of the many receipts for preparing the sensitive solution, we will
give only the two most generally found satisfactory. These are as
follows:
(1) Dissolve one-half ounce of ammonium bichromate in five ounces of
clean water. In another glass dissolve one ounce of grape sugar and one
ounce of gum arabic in five ounces of clean water. When the solutions
are completely dissolved, they should be mixed together, stirred
considerably, and filtered several times.
(2) Dissolve one-half ounce of Le Page’s best fish glue and two ounces
of grape sugar in five ounces of clean water. In another glass dissolve
one-half ounce of ammonium bichromate in five ounces of clean water.
When both are perfectly dissolved, pour the two solutions together, and
stir them well, after which the mixture should be filtered several
times.
These solutions should be prepared in the dark room and should not be
kept more than a day or two, as both light and time will destroy their
power. They should be kept in the dark room in a glass-stoppered bottle.
The sensitive solution, however it may have been made, should be poured
over the clean, dry glass plate already described, as soon as possible
after it is made. This is done in exactly the same manner that
photographers prepare wet plates. The waste solution running off the
glass plate should be filtered and saved as it may be used again. This
pouring must be done in the dark room and dust must be carefully
avoided. The wet plates should now be dried on an iron frame covered
with paper and heated from underneath by a small gas or alcohol lamp.
They should not be heated hotter than the hand can comfortably bear.
When they are perfectly dry, they should be left in the dark room in a
dry, warm place, free from dust and should be used the same day.
The next step is to place the negative that is to be reproduced in a
copying frame with the glass side out. It should be perfectly clean and
free from dust. The sensitive plate is then put in the frame with the
sensitive side towards the negative. Any friction between the plates
must be avoided. This, of course, is done in the dark room. The plates
are now exposed in the sunlight from half a minute to a minute. If
exposed in the shade it will take from five to ten minutes. If the
weather is very damp it is advisable to use a previously warmed
sensitive plate and negative for exposure to the light, since damp
weather injures the sensitiveness of the plate. Also it is well to avoid
any sudden change of temperature during the exposure. In the winter it
is best to make the exposure in a warm room having about the same
temperature as the dark room.
After the exposure is finished, the copying frame should be carried to
the dark room, where the next operation must take place. First, the
exposed sensitive plate should be taken carefully out of the copying
frame and placed on a piece of paper with the sensitive side upward. The
picture will not as yet be discernible upon it. Now place a quantity of
black or brown dry enamel paint on the plate and gently scatter this
powder over it by means of a soft, clean, dry brush, which should be
kept for this purpose only. Then brush the enamel powder back into its
bottle. It is very essential that no dust shall get into it. After five
or ten minutes repeat the powdering and so on two or three times until
the picture is clearly developed.
If the sensitive plate has been underexposed, the picture will develop
rather quickly at the first powdering. This will generally give blurred
reproductions, and it is scarcely worth while to bother longer with that
plate. The only thing to do is to make another exposure. With a well
exposed plate, the picture should develop slowly, that is, not before
the second or third powdering. If the weather has been exceedingly dry,
it is advisable to breathe gently on the exposed sensitive plate before
beginning the powdering. If, on the other hand, the weather has been
damp, the plate should be warmed slightly before powdering.
[Illustration:
FIG. 11. PICKLE POT OR DIP BASKET.
]
When the picture shows clearly, brush all the surplus powder carefully
from the plate, which is now ready to be treated with collodion. Add
about twenty drops of castor oil to a pint of 2 per cent collodion
solution and mix it thoroughly. This mixture, which must be free from
air bubbles, should now be poured over the powdered plate. The waste
collodion which runs off the plate is contaminated by traces of the
enamel paint and cannot be used again. After the collodion has hardened,
cut around the edges of the plate with a knife and then place the plate
with the collodion side upward in a dish containing a weak solution of
caustic potash (half an ounce of caustic potash dissolved in a quart of
water). This solution will remove all the chromium which has served its
purpose. Leave the plate in this solution until the first appearing
yellow coloring has disappeared, and then place it with the collodion
side upwards in a basin with slowly running water, which will in about
an hour wash away all the chromium and potassium salts. The plate should
then be placed in a dish of clean water to which a few drops of nitric
acid have been added, not more than enough, however, to give the water a
slight sour taste. The plate may remain over night in this solution
without harm to the picture, although a couple of minutes will be found
entirely sufficient if one is in a hurry.
Next, the plate should be placed in a large basin of clean water with
the collodion side downwards. If the collodion film has previously been
cut properly around the edges, it will soon separate from the plate,
which may be removed, leaving the collodion film floating in the water.
Meanwhile, the enameled metal plate, which has been prepared exactly the
same as is done for enamel painting, should be cleaned with a soda
solution to free it from all grease. It should now be placed upon a wire
support and carefully brought under the floating film which can be
deposited gently on the enameled surface by means of a soft brush. The
plate should then be taken slowly out of the water and the overlapping
parts of the film should be turned under the edges of the plate, after
which it should be put on a piece of white blotting paper to dry.
If any air bubbles appear under the film, they should be brushed very
gently with a soft, wet brush towards the edge of the plate, where they
will do no harm. If this does not prove successful, the bubbles may be
opened with a needle, after which the air may be pressed out with a wad
of soft paper.
When the plate with the collodion film on it is perfectly dry, the
collodion should be removed by placing the plate in a dish of
concentrated sulphuric acid. Within a few minutes the collodion will
entirely dissolve. When this has taken place, a brownish ring will
appear around the plate, whereupon the plate should be removed at once
and put in a large basin of clean water. Finally, it should be submerged
in a weak solution of ammonia (one ounce of ammonia to a quart of
water), which will neutralize the last traces of the acid, after which
it should be left on a piece of blotting paper to dry.
The picture may now be retouched just as photographers retouch ordinary
photographs, only the same enamel paint should be used that was used in
the powdering process. After the retouching, the plate may be fired in a
muffle, just as is an ordinary enamel painting, and then covered with a
layer of fondant. The finished photograph may, however, be painted with
enamel paints if the enameler desires to make a colored photograph.
------------------------------------------------------------------------
WHERE ENAMELERS’ SUPPLIES CAN BE OBTAINED
ENAMELS, HOWARD M. CHAPIN, 84 Keene St., Providence.
ENAMEL PAINTS, WADSWORTH, HOWLAND CO., Boston.
FURNACES, SIMPLEX TOOL AND SUPPLY CO., Boston.
MUFFLES, SIMPLEX TOOL AND SUPPLY CO., Boston.
GRINDING MACHINES, ABBE ENGINEERING CO., New York.
CARBORUNDUM, CARBORUNDUM CO., Niagara Falls.
WAX BOTTLES, BAKER & ADAMSON CO., Easton, Pa.
ACIDS, PUMICE, ETC., GEO. L. CLAFLIN CO., Providence.
TILES, BECKLEY PERFORATING CO., Garwood, N.J.
FELT, BROWN BROS. CO., Providence.
PAILLONS, HOWARD M. CHAPIN, 84 Keene St., Providence.
DECALCOMANIA FILMS, MALDEN CHINA CO., Malden,
Mass.
MORTARS AND CHEMICAL GLASSWARE, GEO. L. CLAFLIN CO., Providence.
------------------------------------------------------------------------
● Transcriber’s Notes:
○ Missing or obscured punctuation was silently corrected.
○ Typographical errors were silently corrected.
○ Inconsistent spelling and hyphenation were made consistent only
when a predominant form was found in this book.
○ Text that was in italics is enclosed by underscores (_italics_).
○ The use of a caret (^) before a letter, or letters, shows that the
following letter was intended to be a superscript, as in S^t
Bartholomew or 10^{th} Century. .it The use of an underscore (_)
before a letter, or letters, show that the following letter was
intended to be a subscript, as in HNO_{3} (nitric acid).
○ If there is more than one letter in a superscript or subscript
they are enclosed in brackets—{}.
s
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