256 Porcelain ard Earthenware. 
bodies on which they are laid ; and the result is that they crack and 
peel off and not only is the ware defaced, but becomes permeable 
by fluids, is useless, and perhaps falls to pieces. 
Soft porcelain was made at Bow and Chelsea, in England, and 
at the Sevres works, before the disclosures of D’Entrecolles. * It has 
for its base” says M. Brongniart, “a vitreous frit rendered almost 
opaque, and susceptible of being worked with clay, and is glazed 
with an exceedingly diaphanous glass, into which there enters a great 
deal of lead.” It is very white and approaches the condition of 
enamel, which according to the same authority is “‘ glass made opaque 
by the oxide of tin and rendered fusible by the oxide of lead.” 
The vitreous frit alluded to above consists of one part pure clay, 
three parts of a compound of nitre, soda, alum and selenite, with a large 
proportion of sand and a little common salt. Another and better rule 
assigns nine parts prepared flint, nine parts fragments of porcelain 
ground to powder, four parts calcined gypsum, and one hundred 
parts porcelain clay. Arsenic was formerly used at Sevres, for some 
of the work, but the government has ordered a discontinuance of 
that branch of manufacture. Soft porcelain is very beautiful, and 
in the painting and brilliancy of colors the most: perfect specimens 
are scarcely inferior to the Saxon or Chinese; but it does not pos- 
sess the gem like solidity, fineness and translucency, with the almost 
velvet surface of the genuine pieces of those admired manufactures. 
Stone ware isa very perfect kind of pottery, approximating in 
density and infusibility, to the character of porcelain. When prop- 
erly made, it will strike fire from steel. Vessels containing sixty im- 
perial gallons are made of this ware, and are found very useful in 
the arts. 
Lustre ware is produced by giving the surface a metallic covering. 
This is effected after the vessels have been glazed and baked in the 
gloss oven, by mixing the oxide of a metal levigated to a fine pow- 
der with some one of the essential oils, and this mixture is then 
brushed over the surface. ‘They are then taken to the enamelling 
kiln, where “the heat dissipates the oxygen, and restores the metals, 
to their metallic state.” Platina produces a lustre resembling pol- 
ished steel. Gold lustre is of a dark greenish yellow color. 
Of Colors.—Those colors employed in painting on porcelain, 
which will endure the heat of the furnace, are obtained only from 
metallic oxides. M. Brongniart, describes these vitrifiable colors 
