end Jixed ly Fujion on different vitreous Bodies. 34^ 



and -for its covering feld-fpar fufed without an atom of 

 lead. 



This porcelain, which is that of Saxony, is much newer 

 at Sevrc» than the loft porcelain. The colours applied to it 

 are of tuo kinds: the iirll, deftined to reprefent different 

 objects, are baked in a heat very inferior to that neceifarv for 

 baking porcelain. They are exceedingly numerous and vaikd. 

 The othe.s, deftined to he fufed in the fame heat as that 

 which bakes porcelain, lay themlclves flat, and are much lefs 

 numerous. 



The colours of painting are made nearly like thofe deftined 

 for (oft porcelain; they only contain more flux. Their flux 

 is compofed of glafs of lead called rocailie, and borax. I am 

 not yet acquainted with any work which treats on the com- 

 position, life, and effects of thefe colours; fo that it has no 

 where been printed except in one, which might be difpenfed 

 with, that thefe colours fcarcely undergo any change in the 

 fhv, while it has been often written and faid, that the colours 

 for painting in enamel change confiderablv. 



When porcelain is expofed to heat in order to bake the 

 colours, the covering of feld-fpar dilates itfelf and opens its 

 pores, but does not become foft : as the colours do not pene- 

 trate it, they experience none of thofe changes which they 

 undergo on foft porcelain. It muft, however, he faid that 

 they lofe a little of their intenfity by acquiring that tranfpa-* 

 rency which is given to them by fufion. 



When common articles are manufactured, the retouching 

 may be omitted ; but it is neccfTary to give to a painting all 

 the effect that can be deflred : in a word, this retouching does 

 not diftinguifh painting on porcelain from any other kind of 

 painting. 



One of the greater! inconveniences of thefe colours, efpe- 

 cially in the manufactory of Sevres, is the facility with, 

 which they fcale off when expofed feveral times in the fire. 



This inconvenience is obierved more at Sevres than any 

 where elfe, becanfe it depends on the foliditv and infufibility 

 of the porcelain manufactured in that eftabliflunent. But 

 thefe are qualities which make it much longer refill alterna- 

 tions of heat and cold, and which give to its pafte a more 

 linking whitenefs. Paris porcelain, on the other hand, being 

 more .vitreous, more trahfparent, and bluer, often cracks 

 when boiling liquors are put into it. 



To remedy this defect without altering the quality of the 

 pafte, I was of opinion that the cruft. only ou-rht to be fofu 

 ened by introducing into it more filiceous or calcareous flux, 

 according to the nature of the feld-fpar. This method has 



fucceeded ; 



