nnd Jixei Ij Vvjion on different vi(r(QUs Bodies, ig^ 



hand. But it is the only one that changes on hard porce- 

 lain. Its place may be fupplied by a rofe colour from iron 

 V'hich does not change; fo that by fupprelling the carmine 

 made with gold, and fabftituting for it the rofe oxide of iron 

 here alluded to, you may exhibit a palette compofed of colours 

 none of which change in a remarkable manner. This rofe- 

 coloured oxide of iron has been long known; but it was not 

 employed on enamel, bccaufe on that fubftance it changes 

 too much. j^,s the painters on enamel, however, have be- 

 come the painters on porcelain, they have preferved their 

 antient method. 



It might be believed that, by firft reducing to a vitreous 

 inatter the colour called carmine already mixed with its flux, 

 it might be made to affume its laft tint. But the heat ne- 

 ceflary to fufe this vitreous mafs deftroys the red colour, as 

 I have experienced. Befides, it is remarked that, to obtaia 

 this colour very beautiful, it muft be expofed to the fire as 

 few times as poflible. 



The carmine for foft porcelain is made with fulminating 

 gold flowly decompofed, and muriate of filver: no tin enters 

 into it; which proves that the combination of the oxide of 

 this metal with that of gold is not neceirary to the exiftenge 

 of the purple colour. 



Violet is made alfo with purple oxide of gold. A greater 

 quantity of lead in the flux is what gives it this colour, which 

 is almcft the fame crude or baked. 



Thcfe three colours totally difappear when expofed to a 

 great porcelain heat. 



Carmine and purple have given us in glafs tints only of a 

 dirty violet. The violet, on the other hand, produces on 

 glafs a very beautiful cffeft, hut it is liable to turn blue. I 

 have not y^t been abje to difcovcr the caufe of this Angular 

 change, which I faw for the firfl time a few days ago. 



Red, Ro/ef and Broiun Colours exiraBed from Iron. 



Thcfe colours arc made from red oxide of iron prepared 

 with nitric acid. 'l"Jiefe oxides arc further calcined by keep- 

 ing them expofed to the action of heat. If heated too much, 

 they pafs to brown. 



Their flux is compofed of borax, fand, and minium, i{i 

 fmall ([uaiitity. 



Thcic oxides give rofe and red colours capable of fupplving 

 llie place of the fiiine colours made with oxide of gold. vVhcii 

 properly employed on hard porcelain, thvy do not change at 

 all. I have caufed rofcs. to be painted with thefc colours^ 

 And fuuud^jiy dilftrcncc between the baked flower and that 

 B a no* 



