ENAMELLING. 
is fused with feld-spar ; the solvent for ten- 
der porcelain is silex, potash, and lead ; it 
is not volatilized like the preceding, be- 
cause the fire is much inferior to that of the 
hard porcelain. 
These colours being previously fused do 
not in the least change when applied. 
The blues for glass are the same as for 
tender porcelain. 
Concerning Greens. 
The greens, employed in painting, are 
made with the green oxide of copper, or 
sometimes with a mixture of yellow and 
blue. They must be previously melted with 
their flux; without this precaution they 
would become black ; but they do not 
change after the first fusion. 
They must not be treated with a violent 
fire or they would totally disappear. The 
green grounds by strong heat are made with 
the oxides of cobalt and nickel, but it is 
only a brownish green. 
The bluish greens, named sky-blue, for- 
merly a colour very much in esteem, can 
only be used on tender porcelain; they 
always scale off from hard porcelain, be- 
cause there is potash in their composition. 
These greens cannot be used on glass be- 
cause they afford a dirty colour : it is ne- 
cessary to put a yellow on one side, and a 
more or less pale blue on the other, in 
order to produce a green. This colour 
may likewise be fabricated by mixing a 
blue with the yellow oxide of iron. Broug- 
niart hoped to obtain a green from the 
oxide of chrome ; and the experiments he 
made promised to be attended with suc- 
cess. The pure chromate of lead fixed on 
porcelain by means of a strong fire, afforded 
him a very deep and very fixed blue, of 
considerable beauty. 
Concerning Bistres and Brown Reds. 
These are obtained by mixtures of differ- 
ent proportions, of manganese, brown oxide 
of copper, and the oxide of iron, called 
umber. They are likewise previously fused 
in their solvents, so that they do not in the 
least change on tender porcelain; lead 
not having the same action on the oxide of 
manganese as it has on that of iron. This 
colour may be employed very well on 
glass. 
The brown red, ground by strong heat, 
known by the name of fonds cattle, are 
made in the same manner : feld-spar is 
their flux. There is no titanium in their 
composition, though generally asserted in 
VOL. III. 
books. Titanium was not known at Sivre 
when Brougniart first came to that manu- 
factory. He treated this singular metal in 
various ways, and never obtained any 
grounds but a slight obscure yellow, and 
very uncertain in its quality. 
Concerning the blacks. 
Black colours are the most difficult to be 
obtained very beautiful. There is no me- 
tallic oxide which, singly, affords a fine 
black. Manganese gives the best ; iron, an 
opaque, dull, blistered black, which easily 
turns to red. The makers of colours have 
therefore combined several metallic oxides 
which, singly, do not afford blacks, and they 
have obtained a very beautiful colour, but 
it is subject to scale and become dull. 
The oxides are those of manganese, the 
brown oxides of copper, and a little of that 
of cobalt. Grey is obtained by suppres- 
sing the quantity of copper and increasing 
the quantity of flux. 
The Sevres manufactory is the only one 
which has as yet produced beautiful blacks 
with a strong fire. This is more owing to 
the quality of the biscuit than to any pecu- 
liarity of process. It is by a mixture of 
blue with the oxides of manganese and iron 
that they make this very brilliant black. 
The blacks for opaque glass are made the 
same as for painting, by giving different 
doses of solvent. 
After the display of the principles of 
fabricating each principal colour, it is clear 
that by mixing these colours all possible 
shades may be obtained: and also that care 
in the preparation, choice of materials, and 
just proportions of doses, must exhibit very 
sensible differences to the experienced eye 
of a painter. A knowledge of the compo- 
sition of colours does not give the requisite 
care and neatness in making them up. 
On recapitulating the facts here just 
stated, in order to present them in a gene- 
ral view; we see, first, that amongst the 
colours usually employed for hard porcelain, 
one only is susceptible of change, namely, 
the carmine ; and this may be replaced by 
the reds of iron, and then no colour 
changes. 
M. Brougniart presented to the Institute 
an unbaked head made in this manner, and 
a painting of two roses, the one baked and 
the other in its first state. There was not 
any difference between them. 
Secondly, That amongst the colours of 
soft porcelain and enamel, several change 
considerably, particularly the reds of iron 
C 
