a'a Oh ihi t^olburs thtdined froin the metallic Oxides , 



"thef (iatthot ftand a ftrong heat, as it would make them 

 difappear entirely. Green grounds for a ftrong heat are com- 

 pofed with the oxides of cobalt and nickel, but a brownilh 

 glreen only is obtained. 



Blueidi greens called cehjlial ilueSf which were formerly 

 dolours very much in voy:ue, can be applied only upon fott 

 porcelain ; on hard porcelain they conftantly become fcaly, 

 becaufe poiafti enters into their compofition. 



Thefe greens cannot be applied on glafs : they give a dirty 

 colour. To obtain a green on glafs, it is neceflary to put 

 yellow on one lide, and blue, more or lefs pale, on the other. 

 This colour may he made alfo by a mixture of blue with 

 yellow oxide of iron. I hope to obtain from oxide of chrome 

 a direft green colour. The trials I have made give me reafoii 

 to hope for fuccefs. Pure chronvate of lead, which I applied 

 to porcelain in a ftrong heat, gave me a pretty beautiful 

 green of great intenfity and very fixed. 



Bijlres and JluJJek. 



Thefe are obtained by mixtures in different proportions of 

 manganefe, brown oxide of copper, and oxide of iron from 

 ombre earth. They are alfo previoully fufed with their flux, 

 fo that they do not ehange in any manner on foft porcelain, 

 as lead has not the fame a6lion on oxide of manganefe as on 

 that of iron, as I aflured myfelf by an experiment fuiiilar to 

 that already mentioned. 



This colour fades very fpeedily on glafs. 



Ruflfet grounds in a great heat, known under the name of 

 torioije-jhdl grounds, are made in the fame manner. Their 

 flux is feld-fpar: no titanium enters into their compofition, 

 though faid fo in all printed works. Titanium was not known 

 at the manufactory of Sevres when I arrived there. I treated 

 this Angular metal in various wavs, and never obtained but 

 -grounds of a pale dirty yellow, and very variable ia its lone. 



Blacks. 



Blacks are the colours mod difficult to be obtained very 

 beautiful. No metallic oxide gives alone a beautiful black, 

 Manganefe is that which approaches neareft to it. Iron gives 

 an opake, dull, cloudy black, which changes very eafily to 

 Ted: the colour-makers, therefore, to obtain a black which 

 they could not hope for from the beft theorifi, have united 

 feveral metallic oxides which feparately do not give black, 

 and have obtained a very beautiful colour, which, however, 

 is liable to become fcaly and dull. 



