ENAMELLING. 



Montamy says, that glass of lead ought 

 not to be used in the flux or enamel ; he 

 employs borax alone. He then dilutes 

 or makes up his colours in a volatile oil. 



On the contrary, the painters of the ma- 

 nufactory at Sevres use only colours with- 

 out borax, because they dilute them with 

 gum, and borax does not dilute them well 

 this way. M. Brougn.art is convinced 

 that both methods are equally good, and 

 that Montamy is not justified in exclud- 

 ing the fluxes of lead, as they are em- 

 ployed without inconvenience every day, 

 and even render the management of co- 

 lours more easy. 



It is remarked, that in the baking of 

 these colours the glaze is softened so 

 much as to be easily penetrated by them ; 

 and this is one great cause of the change 

 they undergo. They become diluted by 

 the mixture with the glaze, and the first 

 fire changes a painting, apparently finish- 

 ed, into a very slight sketch. 



The oxide of lead contained in the 

 glaze is a more powerful cause of the 

 great changes these colours undergo. Its 

 destructive action is principally exercis- 

 ed on the reds of iron, and is very re- 

 markable. 



It has already been shewn that the two 

 principal causes of the change, which co- 

 lours on enamel and tender porcelain un- 

 dergo, do not relate to the composition 

 of these colours, but entirely to the na- 

 ture of the glass on which theyare placed. 

 The assertion that the colours of porce- 

 lain are subject to considerable change, 

 relates to the colours of soft porcelain, a 

 species of ware now almost totally aban- 

 doned. 



Hence it follows, that the paintings of 

 porcelain require to be several times re- 

 touched and burned, in order to possess 

 the necessary strength. Though these 

 paintings have always a certain softness, 

 they are constantly more brilliant, and 

 never subject to the inconvenience of 

 scaling off. 



Hard porcelain is the second species 

 of ground or excipient for the metallic 

 colours. It is known that the base of 

 this porcelain is a very white argil, call- 

 ed kaolin, mixed with a siliceous and 

 calcareous solvent, and the glaze is no- 

 thing but feldspar fused without an atom 

 of lead. 



This porcelain, which is that of Saxony, 

 is of a much later date at Sevres than the 

 soft or tender. The colours employed 

 are of two kinds ; the first, used for re- 

 presenting different objects, are baked 

 with a very inferior fire to that required 



for baking the porcelain itself. They 

 are verv numerous and varied 



The others, winch require to be fused 

 at as great a heat as that for baking the 

 porcelain, are laid on the general surface. 

 They are much less numerous. 



The colours for painting are made up 

 very nearly of the same materials as those 

 for tender porcelain ; they only contain 

 more flux. This flux is compossd of the 

 glass ot'lead (called rocuille) and of bo- 

 rax. M. Brougniart asserts, that he has 

 not met with any work that treats of the 

 composition, use, and effects of these co- 

 lours. In fact, it has no where been as- 

 serted, in print, that all these colours, 

 except one, are unchangeable in fire ; 

 whereas it has been often asserted, in 

 books, that paintings in enamel are sub- 

 ject to considerable change. 



When the porcelain is put into the fire 

 to bake the colours, the feldspar glaze 

 dilates and opens in pores, but does 

 not become soft. As the colours do not 

 penetrate it, they are not subject to the 

 changes they undergo on tender porce- 

 lain. It must, however, be observed, that 

 they lose a little of their intensity by ac- 

 quiring the transparence given them by 

 the fusion. 



When works of little importance are 

 made, they need not be retouched ; but 

 this is necessary when a painting is to be 

 highly finished. This retouching is not 

 more'distinguishable in paintings on por- 

 celain, than in that of any other species of 

 painting. 



One of the great inconveniences of 

 these colours is, that they scale or fly off 

 when the fire is often applied. 



This has been particularly remarked 

 at Sevres, on account of the solidity and 

 infusibility with which porcelain is there 

 manufactured. But these qual ities cause 

 it to resist the alterations of heat and cold 

 for a longer time, and give its ground a 

 more brilliant colour. On the other hand, 

 the porcelains of Paris being more vitre- 

 ous, transparent, and of a bluish cast, 

 generally crack, if boiling water is fre- 

 quently poured into them. 



In order to remedy this evil, without 

 altering the quality of the body, Broug- 

 niart softens the glaze a little, by intro- 

 ducing more siliceous or calcareous flux, 

 according to the nature of the feldspar. 

 This method succeeded, and for twelve 

 months then past the colours had past 

 two and three times through the fires, 

 without cracking, provided there were 

 not too much flux, and they were not 

 laid on too thick. 



