This is the oil medium that I used on this set of paintings on copper. It is a wonderful medium that is made by Studio Products Inc. I often use it when I am painting in plein-air or when adding a second or third layer of glaze on a painting in the studio. I use it as a couch for the painting; I spread a thin layer of it on my painting surface with a bristle brush and then paint on top of that. It can be used in preparing copper plates before painting as well.