ENAMELLING. 
potters’ white lead, which consists of four 
parts of lead and one of tin, produced a 
very smooth grey enamel, more firm and 
hard than the preceding. A small quantity 
of red oxide of iron gave it a line dark red 
colour. 4. Flint glass, twelve parts ; minium, 
eighteen ; potash, four ; nitre, four ; borax, 
two; oxide of tin three; oxide of cobalt, 
one-eighth of a part, gave a smooth pearl co- 
loured enamel, not brittle or subject to 
crack, and capable of enduring sudden 
changes of heat and cold, as well as the ac- 
tion of oils, alkalies, and weak acids ; but 
it cannot resist the stronger vegetable 
acids, and still less the mineral. 
These enamels were applied only on 
hammered iron, cast iron being too thick to 
be heated with sufficient quickness. But 
they have been applied to the thin cast ves- 
sels in England. It seems unnecessary to 
add, none of them will bear hard blows ; 
and this is perhaps the reason why they 
have not been more used with us. 
The application of enamel colours to 
glass or earthenware constitutes a peculiar 
branch of the ark M. Brougniart, of the 
porcelain manufactory at Sevres, has given 
a good account of them. (Nicholson’s Jour- 
nal, Vol. III. 4to.) 
These bodies may be divided into three 
very distinct classes from the nature of the 
substances that compose them, the effects 
produced on them by the colours, and the 
changes they undergo. These are, 1. ena- 
mel ; soft porcelain, and all the glazes, ena- 
mels, or glasses, which contain lead in any 
considerable quantity. 2 . Hard porcelain, 
or such as is glazed with feldspar. 3. Glass, 
in which there is no lead, such as the com- 
mon window glass. The principles of com- 
position of these colours, and the general 
phenomena they present on these three 
grounds or supporters, are regularly treated 
of. 
Colours in enamel painting have been 
longest known. Enamel is a glass rendered 
opaque by oxide of tin, and very fusible bv 
the oxide of lead. It is this last which in 
particular gives it properties very different 
from those of the other excipients of me- 
tallic colours. Hence all the glasses and 
glazes which contain lead, have the proper- 
ties of enamel, and what we may assert of 
the one will apply to the other with very 
little difference. 
Such are tlie white and transparent 
glazes of Dutch or Delft ware, and the glaze 
of the porcelain called soft ware. 
Tliis porcelain,, the first made in France, 
particularly at Sevres, and indeed for a 
long time almost exclusively at that ma- 
nufactory, lias for its base vitreous frit nearly 
opaque, capable of being acted upon by 
marl, and its glaze is a very transparent 
glass containing much lead. 
The colours made use of are the same as 
those tor enamelling, consequently the 
changes these colours undergo in enamel 
must take place in this species of porcelain. 
The causes of the change being the same in 
both. 
The colours for enamel and soft porcelain 
require less flux than the others, because the 
glass on which they are placed softens 
sufficiently to be penetrated by them. 
This solvent may be either the mixture of 
glass of lead and pure silex, called rocaille, 
or this same glass mixed with that of borax. 
Montamy says, that glass of lead ought 
not to be used in the flux for enamel ; he 
employs borax alone. He then dilutes or 
makes lip his colours in a volatile oil. 
On the contrary, the painters of the ma- 
nufactory at Sevres use only colours with- 
out borax, because they dilute them with 
gum, and borax does not dilute them well 
this way, M. Brougniart is convinced that 
bo tli methods are equally good, and that 
Montamy is not justified in excluding the 
fluxes of lead, as they are employed without 
inconvenience every day, and even render 
the management of colours more easy. 
It is remarked, that in the baking of 
these colours the glaze is softened so much 
as to be easily penetrated by them ; and 
this is one great cause of the change they 
undergo. They become diluted by the 
mixture with the glaze, and the first fire 
changes a painting apparently finished, into 
a very slight sketch. 
The oxide of lead contained in the glaze 
is a more powerful cause of the great 
changes these colours undergo. Its des- 
tructive action is principally exercised on 
the reds of iron, and is very remarkable. 
It has already been shewn that the two 
principal causes of the change which co- 
lours on enamel and tender porcelain un- 
dergo, do not relate to the composition of 
these colours, but entirely to the nature of 
the glass on which they are placed. The 
assertion that the colours of porcelain are 
subject to considerable cliange, relates to 
the colours of soft porcelain, a species of 
ware now almost totally abandoned. 
Hence, it follows, that the paintings of 
porcelain require to be several times re- 
touched and burned, in order to possess the 
