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FARM BUILDINGS IN SOUTH AFRICA 



are linseed oil, red lead — used in the first or priming coat, pigments or 

 colouring matters, litharge or other " driers," and sometimes spirits of 

 turpentine (turps). 



The chief constituents perform the following functions : — 



Some of the linseed oil soaks into the wood to a certain depth, 

 filling up the pores and finally drying into a substance resembling resin 

 which retards decay by excluding air and moisture. 



The remainder of the linseed oil forms, with the white lead, a com- 

 pound which can be easily spread over the surface of the wood, or 

 other material, forming a protective layer. 



The litharge (or other driers) being rich in oxygen, by its oxidising 

 effect on the oil, hastens the drying and hardening of the paint. 



Red lead is also rich in oxygen. It is used with the first or " priming " 

 coat, which it causes to dry hard, thus producing a good base for the 

 remaining coats. 



Picrments are materials of animal or mineral origin, which supply 

 the colour to the paint. These materials are ground in oil when they 

 are to be used for oil paints ; for distemper or water paint they are 

 generally marketed as powders. 



Spirits of turpentine is used merely to save oil, and make the 

 paint more liquid and therefore easier to work. Since it evaporates 

 after the application of the paint, it has nothing to do with protecting 

 the wood or other material painted. 



Proportions of Ingredients. — The proportions of ingredients differ 

 considerably according to the kind of work to be done, climate, and other 

 circumstances. The following is a rough guide for inside work, assuming 

 the materials used to be of good quality : — 



To the last two coats the final colouring matter is added according 

 to depth of tint required, roughly from 1 to 2 ozs. of pigment for every 

 10 square yards of surface to be coated, the quantity of white lead 

 being correspondingly reduced. 



