Jrt of Painting in Enamel, 445 



mercial value varies from 12 to 20 shillings per pound. I have 

 not analysed it, but its constituents, as stated by various au- 

 thors, are silica, an alkali, and the oxides of lead and tin, and, 

 I suspect, as before observed, oxide of antimony also. 



An enamel colour is, like enamel, composed of a colourless 

 and perfectly transparent glass for its base and owes its colour 

 to a metallic oxide. Thus silica, borax, and the red oxide of 

 lead form a base or flux for some colours. The habitudes of 

 the oxides require that each should be treated with reference 

 to its peculiar qualities, for instance, the flux which when em- 

 ployed with gold is best adapted for the production of a beau- 

 tiful colour, is inefficient if used with the oxide of cobalt. 



The plates for paintings are prepared thus: a plate of gold, 

 or more usually of copper *, is covered with three successive 

 layers of enamel, the enamel having previously been ground 

 in an agate mortar; each layer requiring to be passed through 

 the fire and melted before the next is laid upon itf. The 

 plate being thus prepared, the artist proceeds in painting the 

 picture in a similar manner to the painter in oil or in water 

 colours, accordingly as the subject may require. The prin- 

 cipal difference is this, that instead of waiting for the colours 

 to dry before proceeding to lay on another coat, the painter 

 in enamel has his work passed through the fire. By this pro- 

 cess the colours are completely vitrified, and are incorporated 

 with the body of the plate. This is not so completely the case 

 with paintings on glass and on porcelain. The colours on 

 these usually adhere only to the surface, and, under some cir- 

 cumstances, they are known to chip ofF|. Glass and porce- 

 lain, also, do not admit of being subjected to so high a tem- 

 perature as enamel plates, and hence the colours for painting 

 on those substances are manufactured to melt at a much lower 

 degree of heat than those used by painters in enamel. This 



* The French and other Encyclopaedias state, that silver is used for this 

 purpose ; and Walpole, in his "Anecdotes of Painting, &c." says that Petitot 

 used plates of silver. This cannot be correct, for silver has the property 

 of cracking the enamel in all directions every time it is past>ed through the 

 fire, and hence it becomes necessary to expose plates of that metal when 

 enamelled, to a sharp heat, in order to flow the enamel, that the cracks may 

 close. This it is obvious would effectually destroy the drawing of a picture 

 if it did no other injury. Silver is therefore only used for transpareitt 

 enamelling, but in this application it is not so rich and beautiful as gold, 

 and is only employed when the high value of gold is an object of considera- 

 tion, as in the silver stars which are worn by the members of certain orders 

 of knighthood, masonic emblems, military ornaments, &c. 



f For a particular account of the manipulations practised by the ena- 

 meller, see the article Enamelling in Rees's Cyclopaedia. In this article the 

 details are minutely faithful, though with reference to dial-plates modern im- 

 provements have rendered obsolete most of the processes describeil in it 



X See Broneniart " On the colours obtained from the metallic oxides," 

 &c. Phil. Mag. First Series, vol. xiii. p. 342 ct seq. 



