16 



PAINT TECHNOLOGY AND TESTS 



Corn Oil. As a by-product in the manufacture of starch and 

 alcoholic liquids, this material comes into the market having a 

 golden yellow color, and an odor resembling fermented grain. It 

 has a lower drying value than cottonseed oil, and its use in the 

 paint industry will probably be limited to color grinding, where 

 an oil with a semi-drying value is often desired. Like cottonseed 

 oil, it belongs more properly to the soap oil class. It contains 

 glycerides of linoleic and especially palmitic acid. 



ANALYSIS OF CORN OIL 



Rosin Oil. By the dry distillation of rosin, there is yielded a 

 series of heavy dark oils consisting principally of hydrocarbons, 

 resinous bodies, and free acid. These oils vary in their saponifica- 

 tion number from 10 to 60, while their unsaponifiable value aver- 

 ages about 80. Of the grades termed first, second, third, and 

 fourth run, the latter two are superior for use in paints, as a rule 

 containing less free acid than the preliminary runs. Treatment 

 with steam and alkali serve to neutralize the acid nature of the 

 oils and to remove impurities. Refined oils are lighter in color 

 and are often blown and bodied to fairly rapid drying products, 

 especially when treated with manganese driers. Rosin oils are 

 seldom used with lead pigments, on account of the presence of 

 sulphur in the oils, which would result in darkening. Rosin oil 

 paints work very smoothly, even when they are curdled, produ- 

 cing glossy surfaces. The rapid checking of rosin oil paints on 

 wooden surfaces bars the use of this oil for such purposes. 



ANALYSES OF ROSIN OILS 



Hydrocarbon Oils. Several grades of neutral or mineral oils, 

 varying somewhat in gravity, color, and quality, are produced 



