on I he Colours used hi Tainting ly the Ancients. 419 



Vitruvius states that in fresco painting vermilion changed if 

 exposed to light, and he recommends the encaustic process for 

 fixing the colour under this circumstance, namely, laying over it 

 a coat of panic wax, and liquefying the wax so as to make a var- 

 nish for the colour. 



Pliny describes this process as applied in painting ships ; and 

 we know from his authority that several pictures of the great 

 Greek masters were painted in encaustic, and that the different 

 colours were laid on mixed with wax. I have examined several 

 pieces of the painted stuccos found in the different ruins, and 

 likewise the Aldobrandini picture, w^ith a view of ascertaining if 

 any application had been made to fix the colour ; but neither by 

 the test of alcohol, nor by heat, nor by the action of water, 

 could I detect the presence of any wax varnish, or animal or ve- 

 getable gluten. 



The pot of colours to which I have already referred, found at 

 Pompeii, was blackened by smoke, as if it had been recently on 

 a fire of wood, 1 thought that this might be owing to some 

 process for dissolving gluten or varnish in the preparation of the 

 colour ; but I could detect no substance of this kind mixed with 

 the colouring matter. 



Pliny states that gluten (our glue)* was used in painting with 

 blacks : and this specific mention of its application would induce 

 the belief that it was not employed with other colours, which 

 adhered without difficulty to, and were imbibed by, a surface so 

 polished and well prepared as the Roman stucco ; and the liglit- 

 ness of carbonaceous matter alone probably rendered this appli- 

 cation necessary. 



X. Some general Observations. 



It appears from the facts that have been stated, and the au- 

 thorities q\ioted, that the Greek and Roman painters had almost 

 all the same colours as those employed by the great Italian 

 masters at the period of the revival of the arts in Italy. They 

 had indeed the advantage over them in two colours, the Ve-sto- 

 rian or Egyptian azure, and the Tyrian or marine purple. 



The azure, of which the excellence is proved by its duration 

 for seventeen hundred years, may be easily and cheaply made ; 

 I find that fifteen parts by weight of carbonate of soda, twenty 

 parts of powdered opaque flints, and three parts of copper filings 

 strongly heated together for two hours, gave a substance of ex- 

 actly the same tint, and of nearly the same degree of fusibility, 

 and which, when powdered, produced a fine deep sky blue. 



* Lib. XXXV. cap. 25. " Ornne atrainentuiii sole pcilicilur, librarium gum- 

 lui Icclormni duliuo adini.xlo.'' ,.,, 



D <l 2 1 he 



