Rublev Sun-Thickened Linseed Oil from Rublev Colours is a traditional, high-viscosity oil medium made by sun-aging raw, cold-pressed linseed oil in shallow, glass-covered tanks while exposed to air for one year. Sun exposure naturally lightens the oil (and only slightly thickens it). To build a fuller, more bodied handling quality, air is then blown through the oil for at least one additional year, producing a noticeably higher viscosity suitable for painting mediums.

This sun-thickened linseed oil is only slightly more yellow than sun-thickened walnut oil, making it a strong choice for pale colours and whites when you want better flow, smoother levelling, and a richer paint body without modern additives. Use it as a standalone medium or as an ingredient in homemade oil painting mediums. For dilution, it can be paired with traditional solvents such as turpentine, spike oil, or mineral spirits (as appropriate for your process and ventilation).

Linseed oil is a drying oil derived from the seeds of the flax plant Linum usitatissimum, valued for forming strong paint films and long-term durability.

Key properties (at 25°C)

• Appearance: Clear / transparent

• Viscosity: 10,000 cP (Gardner-Holdt: Z)

• Specific gravity: 0.960

• Iodine value: 145–160

• Acid value (max): 2

• Saponification value: 162–172

Health & safety: No known chronic toxicity with intended use. As with all drying oils, dispose of oily rags safely (they can self-heat); store in a sealed metal container or lay flat to dry.