Studio: international art (23.1901)

Enamelling

These enamels can be
mixed together in the cru-
cible to obtain any variety
of colour. All of them
are made by the flux and
the oxides fused together
at an even temperature,
and the quality of their
tone is determined by the
intensity of their fusion and
the intimacy of their com-
bination. There is no
limit to the range of colour,
except that vermilion and
lemon yellow cannot be
obtained.

Enamels are either "soft"
or " hard "—that is, they
are either easily fused at a
comparatively low tempera-
ture or they require a great
heat. An enamel is perfect
when the combination of
the component parts of the
flux, together with the oxide
of metal, is such that there
is no difference of colour,
opacity, or transparency,
throughout the whole mass.

reliquary, illustrating the use of champleve enamel °

south Kensington museum The best way to determine

whether the combination

bined with oxides of metals. The flux is com- is perfect is by dipping a copper rod into the

posed of silica — that is, of powdered flint or crucible and withdrawing it with a part of the

silver sand; minium, which is red lead; nitrate, enamel sticking to the end; pull out the rod

or carbonate of soda, or potash, all melted some distance, so that a fine thread of enamel

together in a crucible until there are no bubbles may be formed; then pass the thread between

left in it. This flux, which is the base of all the thumb and finger, and the slightest difference

enamels, is combined with different metallic of surface will be detected throughout its length,

oxides in various proportions. To a certain point, The quality of the colour will also be perceptible,

beyond which no combination occurs, the more Now, the harder the enamel the greater the

oxide fused with the flux, the darker in tone and quantity of silica contained in it, and the greater

richer in colour will the enamel become, and vice the resistance to atmospheric or chemical action;

versa. Transparent enamels are made opaque the softer the enamel the greater its percentage of

either by the addition of calx, which is a mixture lead and potash, and the more liable it is to be

of tin and lead calcined, or else by arsenious acid, decomposed by atmospheric influences and chemi-

that is to say, of white arsenic. The flux when cal agencies. It is very tempting to use soft

combined with a precipitation of gold and tin, enamels, for at first they look so much more

called purple of Cassius, gives a beautiful purplish- brilliant, and are so much easier to work with, but

red; when combined with oxide of copper, green, there are dangers to which the harder kinds are

blue, and red may be obtained; with oxide of less subject. Thus, when in a state of fusion in

cobalt, a blue; with iron, a brown or orange; with the furnace, dust and foreign matters may injure

manganese, a purple; with silver and gold, an them greatly, dulling the surface and destroying their

orange red; and with stannic acid or oxide of tin, transparency. The soft kinds of enamel contain

an opaque white. a large quantity of lead, and sometimes of borax

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