Ricinoleic is an unsaturated fatty acid that contributes to the conditioning/moisturizing levels, and the stability of lather. This fat has properties attributing to a little slip and glide to the lather. Castor oil is the only common soap making oil known to contain ricinoleic acid, and it’s a super high 90%! The typical range for castor oil added into a recipe is 5%. Castor oil contributes to a boost in lather and will make a recipe trace faster than without adding it.