Determination of changes in mass and volume of linseed oil during drying

Summary

Plates of stainless steel were coated with a thin film of seven different types of oxidative drying oils in order to follow the development charge in mass and volume during 42 days of curing. The plates were weighed in air and in water, and the volumes determined by applying Archimedes’ principle. All of the oils gained considerably in mass, with a maximum of 12% within seven days. The volume, however, decreased with large individual differences from one oil to another. A cold-pressed raw linseed oil decreased in volume by almost 15% whereas the volume of an alkali-refined linseed oil only decreased by a few percent. It is well known that linseed oil-based coatings are prone to crocodiling (surface crack formation), it is suggested that the severity of this phenomenon may be related to the volumetric reduction of the binder during curing. The described method is suggested as a simple means of screening linseed oil binders for formulation and development purposes.