Castor Oil
Saponification values, fatty acid makeup, and what this oil does in a bar of soap.
Saponification values
Grams of lye needed to saponify one gram of castor oil. Multiply by your oil weight, then apply your superfat.
- NaOH (bar soap)
- 0.128
- KOH (liquid soap)
- 0.18
- Iodine
- 86
- INS
- 95
INCI: Ricinus Communis (Castor) Seed OilSaponified name (for labels): Sodium Castorate
Fatty acid profile
| Fatty acid | Percentage |
|---|---|
| Ricinoleic | 90% |
| Oleic | 4% |
| Linoleic | 4% |
Soap qualities at 100%
What a bar made entirely of castor oil would score. Almost nobody soaps a single oil at 100% — this is here so you can see what the oil contributes to a blend. The shaded band is the range most makers aim for in a finished recipe.
What that means in a recipe
Almost entirely ricinoleic acid, which is unusual. It boosts and stabilises lather in small amounts, but makes a soft, tacky bar if it dominates a recipe — most makers keep it in single figures as a percentage.
Almost no cleansing contribution (0) against high conditioning (98). Gentle on skin, but a bar built mainly on this will be slow to trace, slow to harden, and low on bubbles without something to balance it.
Very little hardness (0). Expect a soft bar and a longer cure unless it is combined with a harder fat or butter.
Derived from the numbers above rather than written by hand, so it stays in step with the data. Tendencies, not guarantees — your oils, water, and technique all move the result.
Oils that behave similarly
Closest matches by fatty acid makeup — the usual starting point when you have run out of castor oil and need a substitute. Check the lye maths again after swapping: SAP values differ even between oils that behave alike.
- SoapQuick, conventionalSAP 0.151 NaOH
- Horse OilSAP 0.14 NaOH
- Tallow SheepSAP 0.138 NaOH
- Laurel Fruit OilSAP 0.141 NaOH
- Tallow DeerSAP 0.138 NaOH
Recipes using castor oil
- Castor-Rich Shampoo Bar 12%Castor drives the thick lather people want from a shampoo bar. An acidic rinse afterwards helps hair that feels waxy.
- Conditioning Shampoo Bar 10%Softer and less stripping, aimed at dry or curly hair. Lower coconut, more butter and high-oleic oils.
- Creamy Shaving Bar 10%Tallow and butters for the dense, slick lather a brush can whip up. Traditional shaving soaps often add stearic acid -- worth exploring once you've made this base.
- Honey & Oatmeal 10%A soft, comforting bar. Honey boosts lather and adds sugars that feed bubbles.
- Charcoal & Tea Tree 10%A brisk, deep-cleansing bar. Activated charcoal takes it from grey to near black.
- Rosemary & Mint 10%Fresh and herbal with a strong lather. Jojoba adds slip without much saponified weight.
Sorted by how much of each recipe is castor oil; 11 more recipes use it too. Open the calculator to load any of these from the recipe library.