Natural Pigments Sun-Bleached Linseed Oil is made by exposing raw, cold-pressed linseed oil to sunlight in shallow enamel trays covered with clear glass but exposed to the atomosphere for a period of less than one month. No driers or other additives are used in the making of this oil. The exposure to sunlight lightens the considerably and only slightly thickens it. This linseed oil has about the same color as walnut oil, so it can be used with pale colors and white. This oil can be used as a medium or added to homemade mediums.Use turpentine or mineral spirits as a solvent or diluent for oil painting mediums made with linseed oil. Linseed oil is a yellowish drying oil derived from the dried ripe seeds of the flax plant (Linum usitatissimum, Linaceae).