30 PAINT TECHNOLOGY AND TESTS 



" Four-ounce sample bottles of each oil were sent to the Com- 

 mittee members, with the request to proceed with the tests 

 along the lines agreed upon at the Committee meeting. The 

 instructions for making these tests are outlined as follows: 



(a) A series of small glass plates, approximately 5 by 7 ins., 

 are to be prepared by each member of the Committee. These 

 plates are to be thoroughly cleaned and carefully numbered and 

 weighed upon a chemical balance. The oils to be used for the 

 tests are to be numbered corresponding to the plates. A test 

 of each oil is to be made by painting it upon the surface of a 

 glass plate with a camel's-hair brush, subsequently weighing the 

 plate and the oil. These tests are to be exposed under constant 

 conditions of temperature, if possible, for three weeks' time, 

 making weighings of each plate every day for six days and then 

 every other day for twelve days. 



(b) Another series of tests shall be made, in which 80% 

 of raw linseed oil is to be combined with each of the above 

 oils named. Previous to making any of the tests, there should 

 be added to each oil, or to each combination, 5% of a drier 

 containing lead and manganese. The drier to be used is of the 

 standard grade submitted, together with the oil samples. The 

 results of the tests are to be charted and submitted at the end 

 of the tests, so that they may be compared with the results 

 obtained by each member of the Committee. 



(c) If possible, the oils and mixture of oils used in the above 

 tests are to be ground with pure silica and painted out upon sized 

 paper, three-coat work, the films to be stripped and tested for 

 strength upon a paint filmometer, at two periods two months 

 apart." 



The drying of oils to a firm surface when spread in a thin layer 

 is accompanied by an increase in weight, due to the absorption 

 of oxygen. The percentage of oxygen absorbed often affords a 

 criterion of the drying of the oil under examination, and this 

 factor, together with data regarding the appearance of the oil 

 film, should be taken into consideration when judging the value 

 of an oil or oil mixture. Conditions of light, air, temperature, 

 etc., often cause great variations in the drying of oils arid the 

 percentage of oxygen absorbed, as shown by the results obtained 

 in the following tests. Although it was impossible in these tests 

 to have the conditions under which each experimenter worked 



