Castor Oil — Frequently Asked Questions

Because it is polar where other vegetable oils are not. The hydroxyl group on its ricinoleic acid chains makes the oil polar enough to wet and disperse pigment that a non-polar oil would leave clumped, so it carries high pigment loads evenly. The same hydroxyls make it roughly ten times more viscous than other vegetable oils, which gives the wet, high-gloss film that defines the category.

No. Ricin is a toxic protein present in the castor seed, and it stays behind in the seed meal during pressing and is destroyed by the heat treatment applied to that meal. It is not oil-soluble and is not present in the refined oil. Commercial castor oil is safe to handle and is used in pharmaceutical and cosmetic products worldwide.

Typically 85 to 90 percent, with an iodine value of 82 to 90, a saponification value of 176 to 187 and a viscosity of 650 to 700 centipoise at 25 degrees Celsius. Those values should be confirmed on the certificate of analysis for the specific lot, since grade and origin affect them.

The hydroxyl group again. Ordinary vegetable oils are non-polar triglycerides and are not soluble in alcohol. The hydroxyl on ricinoleic acid makes castor oil polar enough to be miscible with ethanol, which is unusual among vegetable oils and is exploited in alcohol-based formulations and in the manufacture of Turkey Red oil.