Composition of Enameh 395 
tliree parts of white glass, (which contains neither lead 
nor other metallic oxyds,) and one of glass of borax, 
with a half or fourth part of nitre ; yet this calx, so white 
when mixed with the composition of enamel, made with 
enamel sand and the combined oxyd of lead and tin, in- 
stead of increasing, tarnishes the whiteness, and only 
gives a blueish enamel of a livid colour.* Perhaps ena- 
mels, completely made and mixed together in the first in- 
stance, would not produce the same effect ; but this I ne- 
ver tried, I have, however, employed this composition 
as a flux for colours, which, applied afterwards on the 
enamel of earthen-ware, preserved its beauty. I put 
some of this pure enamel also over that of earthen-ware, 
and I think it preserved its whiteness. 
The principal quality of good enamel, and that which 
renders it fit for being applied on baked earthen-ware, or 
on metals, is the facility with which it acquires lustre by 
a moderate heat, (a cherry-red heat, more or less, accord- 
ing to the nature of the enamel,) without entering into 
complete fusion. f Enamels applied to earthen-ware and 
metals possess this quality. They do not enter into com- 
plete fusion; they assume only the state of paste, but of a 
paste exceedingly firm; and yet when baked one might 
say that they had been completely fused. 
There are two methods of painting on enamel : on raw 
or on baked enamel. Both these methods are employed, 
or may be employed, for the same object. Solid colours, 
capable of sustaining the fire necessary for baking the 
enamel ground, may be applied in the form of fused ena- 
* Antimony, employed in any manner as a glazing for eartlien-ware, would be 
more dangerous than lead; even the latter should, if possible, be discard- 
ed. — T illoch. 
f The ingenious author has omitted another principal quality. It ought never 
to contain such a portion of deliquescing salts, as to endanger its being after- 
wards injured by water. This takes place oftener than is generally suspect* 
ed.—TiLLocH. 
