Studio: international art (23.1901)

Enamelling

—a substance that renders them utterly worthless, coloured enamels with the same flux as their base,
The brilliancy and perfection of an enamel will so that it is best to employ those fluxes which are
depend upon the intimate combination of its parts ; most nearly allied. After some experience it is
and this depends largely upon an even temperature possible to ascertain by touch and weight and
being sustained throughout its fusion in the fracture the kind of substances composing a piece
crucible. It is better not to make the enamel of enamel.

from the raw materials, but to obtain the best Silica is procured from flint or sand ; if from
optical Crown glass, and add minium and potash flint, the white flints and the black are better than
in proportions which I shall give further on. It is the yellow, as they contain less iron. The process
advisable to use enamels made with the same base of clarification is interesting. The flints are made
or flux, to prevent their cracking; for instance, an red-hot, then thrown into cold water; after this
enamel heavily charged with lead, if fused upon they are pulverised, sieved, and washed several
one that is made with a large proportion of silica, times. This done, they are treated with hydro-
will crack very readily, and probably peel off in chloric acid to remove all trace of iron, and finally
course of time. It is impossible to obtain all washed once again in water to remove the acid.

Silica has the property of increasing the hardness
of an enamel. The minium or red lead is the
orange-red coloured oxide of lead, which is easily
procurable. It has the power to soften enamels
and to give them a greater degree of expansibility.
The compositions of flux are as follows :—

First, for copper flux and gold flux, take—

4 parts of silica, 6 minium, 12 nitrate of potash ; or
4 parts optical glass, 3 minium, 6 nitrate of potash.
Second, for silver flux, take —

4 parts of silica, 6 minium, 20 nitrate of potash.

Cobalt, oxide of cobalt...... 1 to flux 50 parts.

Green, black oxide of copper I ,, ,, 40 ,,

Yellow, chloride of silver "... I ,, ,, 12 ,,

Ruby, purple of Cassius ... 1 ,, ,, 112 ,,

Ruby, chloride of gold ... 1 ,, ,, 200 ,,

Purple, peroxide of mangan se I „ ,, 200 „

_ , (purple of Cassius I ,, ,, 20 ,,

Orange red < ' , ., . .,

I chloride of silver 2 ,, ,, 20 ,,

White, calx (calcined tin and

lead) .........16 ,, „ 20 ,,

Opalescent yellow, from chloride

of silver and arsenic ... 6 ,, ,, 24 ,,

Yellow, oxide of antimony ... 6 ,, ,, 22 ,,*

Calx is prepared from tin and lead, not only
by melting them together, but by exposing them
whilst melting to the air, in order that the
metals may oxidise. White can be modified
to any extent by the addition of a more densely
coloured enamel, to make it grey or brown,
as the cise may be. To do this the coloured
enamel is pulverised to a granular state, then put
in a crucible and melted in the furnace ; to this is
then added the pounded white enamel, the crucible
being stirred all the time, and the mixture is ready for
the furnace. It may require several firings and good

* It is necessary to note here that every enamel requires a
special treatment in the method of its manufacture, and that
it would require a large volume to discuss the making of
silver gilt beaker with "plique A jour" enamels enamels in all its subtleties. The receipts printed above
(Burgundian, early XV Century) give only a broad idea of the subject.