2 PAINT TECHNOLOGY AND TESTS 



a pale oil of little odor; the oil from Argentine seed often having 

 a greenish tint and an odor resembling sorghum. While filter- 

 ing, pressing and ageing will remove considerable of the (" foots") 

 mucilaginous matter, phosphates, silica, etc., from the oil, the 

 better grades which are intended for varnish making are often 

 refined with sulphuric acid. A light colored oil which may be 

 heated without " breaking " results from this treatment, but 

 such oils are apt to contain considerable free fatty acid, unless 

 they are washed with alkali subsequent to the sulphuric acid 

 treatment. On account of its rapid drying properties and general 

 adaptability for all classes of paints and varnishes, linseed oil 

 has never been supplanted by any other oil. Chemically it 



Field of Flax in bloom in North Dakota 



consists of the glycerides of linoleic, oleic, and isolinoleic acid, 

 its constitution being responsible for its very high iodine value. 



Boiled linseed oil, a heavier and darker product, is made by 

 heating the raw oil in open kettles to high temperatures, generally 

 with the addition of metallic driers such as litharge, and black 

 manganese. The resinates of lead and manganese are often 

 added to oil heated at a lower temperature, to obtain a boiled oil 

 of lighter color. 



By blowing air through linseed oil that has been heated to 

 approximately 200 degrees Fahrenheit, either with or without 

 drier, heavy bodied oils are obtained, which find special applica- 

 tion in varnishes and technical paints. As the viscosity of these 

 oils increase, the iodine values decrease, and a slight rise in 



