The practice of easel painting with oil colours, however, stems directly from 15th-century tempera-painting techniques. Basic improvements in the refining of linseed oil and the availability of volatile solvents after 1400 coincided with a need for some other medium than pure egg-yolk tempera to ...
• Once your impasted layer is completely dry, you can glaze over it with a thin film of paint mixed with a glaze medium. However, in order to prevent cracking, the glaze medium must contain more oil than the layers underneath.