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.
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