Michael Harding's Refined Linseed Oil available in 100ml, 250ml, 1 litre and 5 litre bottles.
Add linseed oil to your oil paints to increase flow. Excessive amounts added to you paints will lead to some apparent yellowing due to the natural colour of the oil. Applying the paint layers thinly is then seen as desirable to avoid other defects of excess such as wrinkling.