Oil -based paints for artists are rather expensive. In addition, some artists prefer to mull their own paints. Just around van Gogh's era, such paints were being manufactured in tubes, a practice continuing today. Some pigments are very expensive. I am studying the mulling of such paints using jojoba oil ( a liquid wax). It is non-drying. I am keeping the paint in pans and ,when ready for painting, I add drops of linseed oil for the drying effect. Residual paint , from the mulling process, is diluted with chemically-modified turpentine ( very low alpha-pinene content) and allowed to evaporate . The residual pigment/ jojoba oil can be recovered for painting utility.