retards drying more than dampness and darkness.

To aid in the inspection of new work, a shop coating of linseed oil is often specified. This does, in a measure, protect the iron from rust, but a very uneven film of dried oil will probably be secured from this method of treatment. Oil applied to a vertical surface runs off until the layer reaches a certain thickness. Where the current meets with an obstruction it piles up into a thick and uneven coating. These thick parts of the layer may require months to harden into a substance firm enough to be fit to paint over. The results are most disastrous in cold weather when oil thickens and contracts. As painters express it, oil, when applied to cold steel, crawls, wrinkles, and crinkles. If linseed oil is used as a primer on steel, it should be  used  hot,  not