โ Scribed by Henry A. Gardner
No coin nor oath required. For personal study only.
THE recent activity of the paint chemist in searching for oils to partly replace linseed oil, has come not only as a result of the present scarcity of the latter commodity, but through a desire to develop a vehicle that will be for certain technical paints even more satisfactory, if possible, than linseed oil.
It is not the writer's intention, however, to encourage the use of so-called substitutes for linseed oil. The market is flooded with them at the present time, and great danger will lurk in their use until their composition is understood or their value determined in a practical way.
The real object of this paper is to present a summary of the results obtained by the writer from a series of experiments on paint vehicles, which may serve to guide other investigators along similar lines of research. The tests outlined herein, although of interest in pointing out the possibilities of the use of many oils other than linseed, are, nevertheless, tentative in nature and subject to confirmation through practical field exposure tests before they are to be accepted commercially.
It is well known that a most desirable feature of paint oils is their ability to set u~ in a short period to a hard surface that will not take dust, that will stand abrasion and offer resistance to moisture and gases. This drying property is dependent upon the chemical nature of the oil. If it is an unsaturated compound, like linseed oil, rapid absorl~ion col oxygen will cause the film to dry rapidly and become hard. If the oil be of a fully satisfied nature, like mineral oil, for example, oxygen cannot be taken up to any great extent and drying will not take place. The various animal and vegetable oils differ in their power of oxygen absorption to a lesser or greater extent. This difference is referred to by the chemist in terms of the iodine value. The iodine value of linseed oil is approximately i9o, meaning that one gramme of the 6il will take up I9o centigrammes of iodine.
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