Oil Paint Additives

There is not a manufacturer I know that will 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 is an important issue to professional artists who are creating art works that they expect to have some degree of longevity. We readily disclose ingredients in our products to assist artists in their creative work.

I will list the most common additives used in the modern manufacture of artists' oils paints and medium:

Additive--Function

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 usage (from most to least common) in the industry.

Notes

1. 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 still maintaining effectiveness.
2. Hydrogenated castor oil, which is a colorless wax when properly added to oil, offers benefits without some of the problems associated with wax. I would be surprised to know of any manufacturer today still using beeswax. Natural Pigments includes this additive (castor wax) in some of our painting mediums, but not in our oil colors.
3. Organoclay usually needs to be 'activated' by mixing it with a polar solvent, such as ethyl alcohol or acetone, and a small amount of water before adding it to the paint mix.
4. Bentonite clay is a naturally-derived mineral that typically requires a polar solvent and water to effectively function.
5. Calcium naphthenate or octoate is typically added with other driers, such as cobalt and zirconium, but can be used alone as a wetting additive.
6. Salts of polycarboxylic acid and modified urea are recently developed additives (within the last 40 years) and are less commonly used in artists' colors, because they are more effective with formulations of high functionality.