262 ON THE NATURE OF DRYING OILS*. 



Experiments. Every colour, and all the tints compounded from it, were 



more brilliant than correfponding tints and colours mixed with 

 the beft drying oils to be procured from the (hops. 

 Paintings ihut Colours mixed with amber, after having been fhut up in a 

 drawer for ieveral years, loft nothing of their original bril- 

 liancy. The fame colours tempered with oils, and excluded 

 from the air, were fo much altered, that they could fcarcely 

 be recognized, 

 colours expofcd Colours tempered with amber were laid on plates of metal, 

 to heatj anr j ex p f e( i (berth in the air and clofe boxes) for a long time, 



to different degrees of heat, from that of the fun in fummer to 

 the ftrong heat of a ftove, without being injured. It is need- 

 lefs to obferve that oil colours cannot undergo the fame trials 

 without being deftroyed. 

 and to folvente; Thefe colours, when perfectly dried in any way, were not 

 acted upon by fpirit of wine and fpirit of turpentine united. 

 They were warned with fpirit of fal ammoniac, and folutions 

 of pot-afh, for a longer time than would deftroy common oil 

 colours, without being injured. 

 They dry very They dry as well in damp as in dry weather, and without 

 wcI1, any fkin upon the furface. They are not liable to crack, and 



are of a flinty hardnefs ; whence it appears that this vehicle 

 poflefles every deferable property, and it is prefumed may be 

 a difcovery of fome importance to artifts. 

 Gum copal nearly Having fucceeded thus far with amber, I tried the fame 

 as good as am- ex p er i me nts upon folutions of gum copal, which is nearly as 

 brighter, hard and infoluble as amber itklf. The refult of thefe was 



the fame as the former, except that with the copal the colours 

 were fomethjng brighter than with amber. As it is extremely 

 troublefbme to diflblve the copal and amber, I tried thofo 

 folutions of them in oil which are fold in the (hops. When 

 good, I found them to anfwer as well as my own. This is a 

 great convenience, as many might be deterred by the difficulty 

 of preparing this vehicle, who may willingly ufe it, as it 

 is thus to be procured without that trouble. 



flw Metliod ofufing the Solution of Amber or Copal, as a Vehicle 

 for painting. 



Inftrucllons for The cloth or other fubftance to be painted on, mould be 

 the ufe of am- prepared with fome colour fully faturated with drying oil ; or 

 vehicie C for 3 pabt- ^ w ^ be Detter done with the fame vehicle to be ufed in 

 xng. painting, 



