Modern Oil Paint Additives

Most manufacturers of artists’ paints do not readily disclose information about additives for the simple reason they view it as proprietary information. Natural Pigments and our brand of artists’ oils, Rublev Colours, have eliminated this problem by not including any stabilizing or dispersing additives. Hence there is nothing to disclose except for the pigment and vehicle. We believe transparency and disclosure are essential issues for professional artists creating artworks that they expect to have some degree of longevity. We readily disclose ingredients in our products to assist artists in their creative work.

We list the most common additives used in the modern manufacture of artists’ oils paints and mediums:

Additive and Their Functions

Aluminum stearate Pigment dispersion and wetting, and pigment suspension
Magnesium stearate Pigment dispersion and wetting, and pigment suspension
Hydrogenated castor oil Rheological additive for thixotropic flow for pigment suspension
Organoclay Pigment suspension
Bentonite clay Pigment suspension
Calcium naphthenate or octoate Pigment wetting and drier
Salt of polycarboxylic acid Pigment wetting, dispersing, and deflocculation
Modified urea Rheological additive for thixotropic flow to prevent pigment settling

The above list is ordered according to the industry's usage (from most to least common).


  • Stearates are usually added from 1 to 2% of the total weight of the pigment in the formulation. Some manufacturers add more, while others add the least possible while maintaining effectiveness.
  • Hydrogenated castor oil is a colorless wax that offers benefits without most problems associated with other waxes when properly added to the oil. Natural Pigments includes this additive (castor wax) in some painting mediums, but not in Rublev Colours Artists Oils.
  • Organoclay usually needs to be ‘activated’ by mixing it with a polar solvent, such as ethyl alcohol or acetone, and sometimes a small amount of water before adding it to the paint mix.
  • Bentonite clay is a naturally-derived mineral that typically requires a polar solvent to function effectively in oil-based paint.
  • Calcium naphthenate or octoate is typically added with other driers, such as cobalt and zirconium, but can be used alone as a wetting additive.
  • Salts of polycarboxylic acid and modified urea are recently developed additives (within the last 40 years). They are less commonly used in artists’ colors because they are more effective with formulations of high functionality.