ENAMELLING. 419 



snuffboxes, etuit, &c. &c. will not conceive much difficulty in this 

 use of (he glass. It may be managed by the aid of a machine some- 

 what similar to, but more powerful than, a common printing press, 

 with a solid metal platine, to fit and fill the frame, as above ; though 

 much better contrivances may be found among the multifarious en. 

 gines employed at Birmingham for the purposes of coining, and 

 striking the heavy dies, t:,an any we can possibly suggest. In 

 whatever manner the two glasses may be pressed into union, the 

 united body may be afterward ground ami polished. 



[Pantologia. Walpole. 



SECTION III. 



Enamelling. 



THB delicate and beautiful art of enamelling consists in the 

 application of a smooth coating of vitrified matter (transparent or 

 opaque, and with or without colour, figures and other ornaments), 

 to a bright polished metallic substance. It is, therefore, a kind of 

 varnish made of glass, and melted upon the substance to which it 

 is applied, and affording a fine uniform ground for an infinite vari. 

 ety of ornaments which are also fixed on by heat. 



The general principles on which enamelling is founded, are on 

 the whole very simple, but, perhaps, there is none of all the che- 

 mico- mechanical arts which requires, for the finer parts, a greater 

 degree of practical skill and dexterity, and of patient and accurate 

 attention to minute processes. 



The concealment observed by those who profess this art is pro- 

 portioned to the difficulty of acquiring it ; the general chemist 

 must, therefore, content himself with the general principles of 

 enamelling, and the detail of those particulars that are commonly 

 knon. 



Though the term enamelling is usually confined to the ornamen. 

 tal glazing of metallic surfaces, it strictly applies to the gl.izin" of 

 pottery or porcelain, the difference being only that in the latter the 

 surface is of baked clay. With regard to the composition of co- 

 loured enamels (which are all tinged by different metallic oxyds ) a 

 very general account of the substances used will suffice in this 

 place, the rest of the subject having been treated of in the 

 article of coloured glass. The enamelling on metals, therefore, will 

 only be noticed in this place. The only metals that are enamelled, 



V E 2 



