39^ Researches respecting the 
ingly white enamel, which may serve also as a flux fol 
purple, and particularly for blue. 
Sixty parts of enamel sand or less, thirty of alum, 
thirty-five of sea salt, and a hundred of minium, or any 
other oxyd of lead, give a white enamel when the 
fluxes do not predominate too much, and a gelatinous 
glass when a great deal of fluxes has been added. 
This glass is good for red, and the enamel may be ap- 
plied to all kinds of clay capable of sustaining a strong 
heat. 
It is of great importance to remark, and to know, that 
the sand employed for enamel must not be sand which 
contains only silex : sand of that kind alone is of no use. 
The sand proper for this purpose is that which contains 
talc with silex. To make a sand proper for enamel and 
the fluxes of colours, &c. there must be nearly one part 
of talc and three of siliceous sand. 
What appears to me most essential in regard to the suc- 
cess of enamel, is the choice of sand. It is very possible 
to compose this saml by art; and though I have not de- 
composed it, I have found by synthesis, that three parts 
of siliceous sand and one of talc form an excellent sand 
for enamel. From this it may be readily seen, that, to 
compose with facility sand for enamel, nothing is necessa- 
ry but to determine, by a good analysis, the quantity of 
talc. This sand may be procured in places where 
earthen-ware is made. It may be easily known ; for, be- 
sides the siliceous sand, which forms the greatest part of 
it, you may observe in it talcky particles in great abun- 
dance ; and, to be good, it must contain nearly a quarter. 
When it does not contain a sufficient quantity, the ena- 
mel it produces fuses with more difficulty, and does not 
become smooth; it remains granulated and pitted. There 
are certainly some combinations of earth which may pro- 
duce very good fluxes, either for enamel or for transpa- 
