Chemical Aids to Art. 409 



CHEMICAL AIDS TO ART.— No. II. 



BY PROFESSOR CHURCH,, M.A. 



Of the Royal Agricultural College. 



I purpose describing, on the present occasion, several methods 

 for the permanent artistic decoration of wall surfaces. In our 

 climate the processes of distemper and fresco painting have 

 some serious drawbacks. The size used with the colours in 

 distemper is liable to perish, while the dust and soot which 

 accumulate on the decorated surfaces cannot be removed by 

 any cleaning process, save, to a certain extent, by washes of 

 spirits of wine. Besides the mechanical difficulties of fresco 

 painting, which often hinder so seriously the artistic perfection 

 of the works executed by this method, it is by no means certain 

 that the painting will be permanent, even when every care has 

 been taken. The experience of Italy in this matter must not 

 be accepted as a sure guide for our own artists. The enormous 

 size of our great cities, and the vast amount of coal and gas 

 consumed in them, render their atmospheric conditions very 

 unfavourable for the permanence of works in fresco. As such 

 artistic works will probably for some time to come be executed 

 only in large towns, it is greatly to be desired that some pro- 

 cess of painting at once easy and permanent, could be devised. 

 Many attempts have been made in this direction, and the success 

 already attained has been, no doubt, considerable. I shall 

 describe the chief features of several more or less novel pro- 

 cesses of wall painting, pointing out here and there their ad- 

 vantages and disadvantages, and also offering, where practi- 

 cable, some hints for their alteration and improvement. 



As a new method of painting, intimately depending on 

 recently discovered chemical facts, first and foremost stands the 

 process called water-glass fresco, or stereochromy. The 

 plastered wall is partially saturated with a weak solution of 

 the soluble silicate of potash (made by boiling calcined flints, 

 which have been etonne in cold water, with caustic potash 

 under pressure); the wall is allowed to dry, and then the 

 painting is commenced. Ordinary fresco colours are employed, 

 but the only white to be used is zinc white. Some colours, 

 those which are affected by alkalies, cannot, however, be used 

 with success. Among these, the chrome yellows, the lakes, 

 several of the madder colours, and all the copper and arsenical 

 greens, are inadmissible. All colours, on the other hand, which 

 are not acted upon by alkalies, such as vermilion, smalt and 

 chrome green, with the yellows and reds made from iron oxides 



