28 PAINT TECHNOLOGY AND TESTS 



that a certain varnish will dry quicker when exposed to the light 

 than when in the dark. 



Chevreul was one of the first pioneers in this field of research 

 to observe the effects of colored lights on drying, and he claimed 

 that oil exposed under white glass dried more rapidly than 

 when exposed under red glass, which eliminates all light of short 

 wave lengths. 



Genthe obtained interesting results in the drying of oil sub- 

 mitted to the effect of the mercury lamp. Oxidation without 

 driers was effected probably through the formation of peroxides. 

 In commenting on this subject, Blackler l gives a description of 

 the use of the Uveol Lamp, which is similar to the mercury 

 lamp, but has, instead of a glass casing which cuts off the valuable 

 rays, a fused-quartz casing which allows their passage. 



Driers in Boiled Oil. In the boiling of linseed oil, by certain 

 processes the oil is heated to 250 F. and manganese resinate 

 is incorporated therein. It goes into solution quite rapidly. 

 In other processes the oil is heated to 400 F. or over, and 

 manganese as an oxide is boiled into the oil. Although it is 

 unsafe to say that a small percentage of rosin, such as would be 

 introduced by the use of resinate driers, is not harmful, yet it 

 appears that this process should give a good oil, inasmuch as it 

 has been found that no matter whether the manganese is added 

 to the oil, as a resinate, borate or oxide, practically the same 

 drying effect is noticed in every case where the percentage of 

 manganese is the same. It is the opinion of some, however, 

 that the resinate driers are not as well suited for durability as 

 oxide driers. However, if a boiled oil is found to contain on 

 analysis a small percentage of rosin less than 0.5% or a 

 percentage only sufficient to combine with the metal present, 

 it should not be suspected of adulteration. Practical tests 

 should be made with such oil along with an oil made with 

 an oxide drier, before pronouncing on their relative values. 

 Inasmuch as the addition of certain driers to linseed oil lessens 

 the durability of the film, it is more practical to use the smallest 

 amount of drier that will serve the purpose desired, that is, 

 set the oil up to a hard condition which will not take dustr and 

 which will stand abrasion. 



M. B. Blackler: "The Use and Abuse of Driers," P. and V. Society, 

 London, Sept. 9, 1909. 



