' 84 Engraving on Steatites. 



Steatites, uhen exposed to heat, may be coloured by so- 

 lutions in oils, in alcohol, in acids, and in alkalies. 



Colours which dissolve in amber varnish, such at verdi- 

 gris, ochre, Sec, connimnicate their tints to baked stea- 

 tites : for this purpose it must be heated on a charcoal fire. 

 Colours dissolved in turpentine 2;ive a brighter tint. 



Solutions in spirit of wine, of carthamus, gamboge, log- 

 wood, dragon's bl'ood, &c., communicate their tints to 

 steatites when left immersed in them for some hours. 



A solution of gold in nitro-muriatic acid gives to heated 

 steatites a light or a dark purple colour, according to the 

 strength of the solution. Muriate of silver by the help of 

 sulphuric acid gives a black colour. Indigo dissolved in 

 the same acid gives to this stone a blueish gray colour. If 

 steatites, coloured by a solution of gold, or by muriate of 

 silver, be exposed to a strong heat, it acquires a kind of 

 metallic splendor like that of gold or of silver. 



When the stone is heated, coloured acid solutions may 

 be applied, so as to produce great brightness and neatness i 

 on this accoimt a particular colour may be given to the 

 ground of the cameo. Sulphuric acid is more efficacious 

 than the muriatic or nitric acids. The oxalic acid may be 

 employed ; also coloured alkaline solutions, and particu- 

 L'lrly that of indigo, may likewise be used : most of the 

 colours sink the eighth of a line into the stone. 



When steatites has been baked it is polished with emery 

 and common polishing stones, and also with tin and tri- 

 poli : it assumes then a brilliant splendour, and resembles 

 agate, jasper, chalcedony, &c. 



This stone, on account of its softness, is exceedingly 

 proper for the purposes of the engraver : by using it he can, 

 perform as much work in a day as he could in a week by 

 employing harder stones : he may then by means of heat 

 give his work a great degree of hardness, and render it 

 durable. 



Experience shows that the hardness of gems, brilliancy, 

 and the agreeable colours of agate, may be given to the 

 soft and opakc steatites, known under the name of lard 

 stone or Spanish chalk. 



The artist, who by engraving on gems, immortalizes the 

 image of a great man, or the remembrance of a remarkable 

 event, devotes his talents and his genius to a noble branch 

 of the fine arts. . Cameos and intaglios, therefore, are in- 

 teresting monuments of the Egyptian, Carthaginian, Gre- 

 cian and Roman histories. They were objects of study and 

 5 ' amuse- 



