And why is it so expensive? Oil paint has been used for hundreds of years. It's made from a drying oil, like flaxseed, and pigment sometimes with fillers and thickeners added to the mix.

The oil obtained from flaxseed ... it is none the less true that their use greatly facilitates [the setting and drying of paint, a very desirable thing under many circumstances.

Thus drying linseed oil, which is made by boiling ... and it is then mixed with common oil paint. For inside work in houses it will answer well, but it should never be applied to the outside ...