Linseed oil makes the strongest paint film available. Newer formulas of refined linseed oil minimize yellowing. Purer and more refined than hardware store oils, these linseed oils can slow drying times, increase gloss and allow tinted glazes to achieve any desired effect. Choose from Gamblin, Holbein, Best Test, Grumbacher & Winsor & Newton brands. Artist grade of linseed oil should not be confused with the hardware store grades of this medium. The lower quality linseed oil available at hardware stores will cause oil paints to become gummy and sticky as well as weakening the paint structure.