Linseed Oil, flax

Saponification values

Grams of lye needed to saponify one gram of linseed oil, flax. Multiply by your oil weight, then apply your superfat.

NaOH (bar soap)

0.135

KOH (liquid soap)

0.19

Iodine

180

INS

-6

INCI: Linum Usitatissimum (Linseed) Seed Oil

Fatty acid profile

Soap qualities at 100%

What a bar made entirely of linseed oil, flax 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.

• Hardness9
• Cleansing0
• Conditioning90
• Bubbly lather0
• Creamy lather9

What that means in a recipe

Almost no cleansing contribution (0) against high conditioning (90). 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 (9). Expect a soft bar and a longer cure unless it is combined with a harder fat or butter.

High in polyunsaturated acids (linoleic and linolenic together, 63). These are the ones associated with the orange spots and rancid smell that develop in older bars, so use fresh oil, keep the percentage modest, and do not expect a long shelf life.

A high iodine value (180) points the same way: more unsaturated, softer, and quicker to go off than a saturated fat.

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 linseed oil, flax and need a substitute. Check the lye maths again after swapping: SAP values differ even between oils that behave alike.

• Flax Oil, linseedSAP 0.135 NaOH
• Camelina Seed OilSAP 0.134 NaOH
• Perilla Seed OilSAP 0.135 NaOH
• Sacha Inchi, Plukenetia volubilisSAP 0.134 NaOH
• Sea Buckthorn Oil, seedSAP 0.139 NaOH