kama's walnut oil is a first-pressed, semi-drying siccative oil. Semi-drying oils are a subcategory of siccative oils, defined as containing a lower concentration of the free fatty acids that are responsible for the chemical reaction allowing siccative oils to dry : to pass from a liquid to a solid state via a complex chemical reaction. This oxidation reaction is not only responsible for the drying of paints but also for their aging since it continues beyond that. drying, thus causing the yellowing of oil colors in the years following the completion of the work.
Since these fatty acids are present in lower proportions, walnut oil, like other semi-drying oils, oxidizes and ages at a much slower pace that linseed oil the traditional binder of oil paints and mediums.
Safety Instruction sheets for this product can be found on Kama Pigments website