Castor Oil

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

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Fatty acid profile

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.

• Hardness0
• Cleansing0
• Conditioning98
• Bubbly lather90
• Creamy lather90

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

• Vanilla Hearth 18%Cocoa butter and castor give a dense, creamy, big-bubbled lather. Built for vanilla and cinnamon leaf at roughly 3% of oil weight. Note the castor is unusually high - expect a slightly tacky bar until it is fully cured.
• 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.
• Gentle Grove 12%Olive and soybean with a generous slug of castor. Very low cleansing and very conditioning. A soft bar that traces slowly and wants a long cure.
• 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.

Sorted by how much of each recipe is castor oil; 16 more recipes use it too. Open the calculator to load any of these from the recipe library.