On the Composition of Enamel. 389 
Mr. Cumberland’s instruments appear to promise great 
utility in the first and last of these processes ; that is, they 
may be used either with or without a fretting powder. 
There are however many objections to their being used 
to grind speculmns ; not only with regard to the intended 
figure, but the nature of the material. 
William Nicholson. 
N o. 78. 
Researches respecting the Composition of Enamel . By 
C. Clouet, Associate of the French National Insti- 
tute.* 
White Enamel. 
White enamel, either for earthen- ware, or the pur- 
pose of being applied on metals, is composed in the fol- 
lowing manner: You first calcine a mixture of lead and 
tin, which may be varied in the following proportions ; 
viz. for 100 parts of lead, 15, 20, 30, and even 40 of tin. 
A mixture of lead and tin calcines very easily in contact 
with the air. As soon as this mixture is brought to a red 
heat, nearly a cherry colour, it burns like charcoal, and is 
calcined very speedily. The composition which cal- 
cines best, is that which in 100 pounds of lead contains 
from 20 to 25 of tin. The tin here meant is pure tin. In 
proportion as the calcination is effected, you must take 
out the calcined part, and continue to oxydate the rest 
until the whole has become pulverulent. As some small 
particles always escape calcination, you must expose to 
the fire a second time the oxyd obtained in order to cal- 
cine it completely ; which may be easily known by its 
* Tilloch, vol. 7, p. 3. From the Annalcs de Chimie, 
