Due to its lathering ability, it’s a common ingredient in other soapy products such as solid bubble bath. It also adds shine and slip to lip products.

Castor oil is extracted from the seeds of the castor oil plant. The seeds are pressed to extract the oil within. It has a unique fatty acid profile, with 85-95% ricinoleaic acid, 2-6% oleic acid and 1-5% linoleic acid. In addition to bath and beauty products, castor oil is used in food and as a coating and lubricant in various industries.

In cold process soap, castor oil is typically used around 2-5% of the total oil weight. I’ve found using more than 10% can lead to a slightly sticky bar. Even a small amount of castor oil (such as 1%) contributes to a stable and fluffy lather. Substituting castor oil for another oil in recipes is tricky; there is not another fixed oil that adds quite the same properties.