ENAMELLING. 
necessary strength. Though these paintings 
have always a certain softness, they are 
constantly more brilliant, and never subject 
to the inconvenience of scaling off. 
Hard porcelain is the second species of 
ground or excipient for the metallic co- 
lours. It is known that the base of this 
porcelain is a very white argil, called 
kaolin, mixed with a siliceous and calcareous 
solvent, and the glaze is nothing but feld- 
spar fused without an atom of lead. 
This porcelain, which is that of Saxony, 
is of a much later date at Sevres than the soft 
or tender. The colours employed are of 
two kinds, the first used for representing 
different objects are baked with a very in- 
ferior fire to that required for baking the 
porcelain itself. They are very numerous 
and varied. 
The others, which require to be fused at as 
great a heat as that for baking the porcelain, 
are laid on the general surface. They are 
much less numerous. 
The colours for painting are made up 
very nearly of the same materials as those 
for tender porcelain; they only contain 
more flux. This flux is composed of the 
glass of lead (called rocaille) and of borax, 
M. Brougniart asserts, that he has not met 
with any work that treats of the composi- 
tion, use, and effects of these colours. In 
fact, it has no where been asserted, in print, 
that all these colours, except one, are un- 
changeable in fire ; whereas it has been 
often asserted, in books, that paintings in 
enamel are subject to considerable change. 
When the porcelain is put into the fire to 
bake the colours, the feldspar glaze dilates 
and opens in pores, but does not become 
soft. As the colours do not penetrate it, 
they are not subject to the changes they 
undergo on tender porcelain. It must, 
however, be observed, that they lose a 
little of their intensity by acquiring the 
transparence given thereby the fusion. 
When works of little importance are 
made, they need not be re-touched ; but 
this is necessary when a painting is to be 
highly finished. This re-touching is not 
more distinguishable in paintings on porce- 
lain than in that of any other species of 
painting. 
One of the great inconveniences of these 
colours is, that they scale or fly off when the 
fire is often applied. 
This has been particularly remarked at 
S6vres, on account of the solidity and infusi- 
bility with which porcelain is there manu- 
factured. But these qualities cause it to. 
resist the alterations of heat and cold for a 
longer time, and gives its ground a more 
brilliant colour. On the other hand, the 
porcelains of Paris being more vitreous, 
transparent, and of a blueish cast, generally 
crack if boiling water is frequently poured 
into them. 
In order to remedy this evil, without al- 
tering the quality of the body, Brougniart 
softens the glaze a little, by introducing 
more siliceous or calcareous flux according 
to the nature of the feldspar. This method 
succeeded, and for twelvemonths then past, 
the colours had past two and three times 
through the fires without cracking, provided 
there were not too much flux, and they were 
not laid on too thick. 
It has been remarked, that when soda and 
potash have been introduced, the colours 
scaled, so that they cannot be used as 
fluxes. These alkalies being volatilized, 
abandon the colours which cannot adhere to 
the glaze by themselves. 
It has been observed, that other colours 
are likewise prepared, which being laid 
upon the general surface, are fused by the 
same fire as bakes the porcelain. These 
colours are but few, because there are few 
metallic oxides that can support such a fire 
without being volatilized or discoloured. 
Their solvent is the feldspar. As they in- 
corporate with the glaze they never crack, 
and are more brilliant. 
The third receptacle of metallic vitri- 
fiable colours is glass without lead. 
The application of these colours consti- 
tutes the art of painting upon glass ; an art 
much practised in former ages, but which 
was, till lately, supposed to be lost, because 
out of fashion. It, however, too immedi- 
ately depends on the art of painting on ena- 
mel and porcelain to be lost. Descriptions 
of the processes may be found in different 
books. 
A book entitled, “ L’Origine de 1’art de 
la Peinture sur Verre,” published at Paris in 
the year 1693, and “ Le Traits de Part de la 
Verriere,” byNeri andKunckel, seem to be 
the first works containing complete descrip- 
tions of this art. Those published since, 
even the great work of Leviel, which consti- 
tutes part of “ Les Arts et Metiers,” of the 
French academy, and of the “ Encyclopedic 
Methodique,” are only compilations from 
the two former works. 
It is somewhat remarkable, that if we 
follow the processes exactly as they are 
described in these works, as our author has 
done with some of them, the colours of 
