Refined linseed oil is frequently used to thin paint and to make it shine more by giving it a smoother appearance. Dilute the oil with turpentine or mineral spirits to use as a medium. Linseed oil is a clear oil extracted from the seeds of the flax plant that tends to yellow over time and in the dark, it is more drying and resistant than most other oils. However, avoid using too much of it if you don't want your paint to become 'sticky'. Size: 75 ml.