60 CASEIN. 



noting that the addition of petroleum, benzol, or the like, 

 causes the particles of the paint to penetrate deeply into 

 wood and the fine joints in ironwork without stopping the 

 circulation of air. This protects the iron from rusting ; and 

 the antiseptic effect of the petroleum preserves wood from 

 rotting and fungoid growths. Oil paint is soon spoiled in 

 Appearance when exposed to ammoniacal exhalations, but 

 they have no effect on petroleum-casein paints. The latter 

 dry readily and do not darken in course of time ; neither does 

 the smell of petroleum hang about them very long. 



Petroleum may be replaced in these paints by benzol, 

 turps, naphtha, xylol and ethereal oils like oil of spike laven- 

 der, etc. When the paint is to be used for outside work on 

 timber or brickwork an addition of linseed oil is desirable, 

 and the paint should be thinned down considerably so as to 

 allow the particles to penetrate deep into the underlying 

 material. 



In places exposed to mechanical or atmospheric influences, 

 or on damp walls, these quick-drying casein paints will be 

 found highly advantageous. 



BOILED OIL SUBSTITUTE. 



A substitute for boiled oil may be prepared by adding 

 to 100 parts by weight of casein 10 to 20 parts of a 1 

 to 10 per cent, solution of soap, followed by 20 to 25 

 parts of slaked lime, the mixture being carefully kneaded 

 until a homogeneous mass is formed. It is afterwards 

 thinned by the gradual addition of 20 to 40 parts of turps 

 and sufficient water to bring the consistency down to that of 

 boiled oil. If the varnish is to be kept for any length of 

 time, a little ammonia should be added to prevent the pre- 

 cipitation of the calcium caseate. This substitute is much 

 cheaper than boiled oil, and dries so quickly that the paint 

 made with it can be applied in two coatings in immediate 

 succession. 



