Sal butter in soap making
Published by The Soap Brain Team
Sal butter is a hardening soap-making oil rich in stearic acid (45.1%). A gram of it turns to soap with about 0.132 g of NaOH (lye). It firms up a bar with a stable, creamy lather and blends well with conditioning oils. Most soapers use it at 10–30% of their oils.
Fatty-acid profile
Sal butter is mainly a hardening oil: its saturated fatty acids give a firm, long-lasting bar with a stable, creamy lather, and it is usually blended with more conditioning oils to keep the finished soap mild.
Sal butter is about 51% saturated fat and 40% unsaturated — that saturated majority is what lets it firm up a bar and hold a stable lather.
| Fatty acid | Share | What it does in soap |
|---|---|---|
| Stearic acid | 45.1% | a saturated fatty acid that adds hardness and a thick, stable lather; a large share can speed up trace |
| Oleic acid | 38.2% | a monounsaturated fatty acid that makes a gentle, conditioning, moisturising bar with a slick, lower lather and a slower trace |
| Palmitic acid | 6% | a saturated fatty acid that builds a hard, long-lasting bar with a stable, creamy lather |
| Linoleic acid | 2% | a polyunsaturated fatty acid that is very conditioning but oxidises readily — a driver of DOS (dreaded orange spots) at high levels |
| Linolenic acids (C18:3) | 0.3% | the polyunsaturated C18:3 family — deeply conditioning but the most prone to rancidity; keep the combined polyunsaturated total modest |
Sal butter in the bar
Expect a dense, low-bubble, creamy lather from Sal butter — rich and steady rather than foamy. Pairing it with a bubbly oil adds the fluffy bubbles it lacks.
Because it is rich in palmitic and stearic acids, Sal butter tends to bring a batch to trace quickly and set up fast, so work briskly and keep fragrances that accelerate trace in mind. The upside is a firm bar that usually unmoulds within a day or two.
In a blend Sal butter is a hardening, bar-firming component. Use it in small amounts; combine it with conditioning liquid oils so the bar stays mild rather than brittle.
Closest substitutes for Sal butter
Out of Sal butter? These oils behave most like it in a bar — ranked by how close their hardness, cleansing and conditioning profile and lye (SAP) requirement are. The numbers are predicted properties for a 100% single-oil bar, not a safety guide; always recalculate the lye when you swap an oil.
| Oil | Hardness | Cleansing | Conditioning | SAP (NaOH) |
|---|---|---|---|---|
| Sal butter (this oil) | 51 | 0 | 40 | 0.132 |
| Cupuaçu butter, deodorized | 50 | 0 | 41 | 0.135 |
| Cupuaçu butter, refined | 50 | 0 | 41 | 0.135 |
| Kokum butter | 59 | 0 | 38 | 0.134 |
| Tallow (beef fat) | 52 | 3 | 46 | 0.138 |
Using Sal butter in a recipe
One gram of Sal butter needs about 0.132 g of NaOH (sodium hydroxide) to turn fully to soap, within a documented range of 0.13–0.139 g/g across sources. The calculator below uses this value; always confirm the lye weight before you mix.
Its iodine value is about 40 — a low value, pointing to a hard, long-lasting bar with good shelf life. Iodine value is only a rough guide, not a hard rule, but it gives you a feel for how a bar built around this oil will wear.
Most soapers use Sal butter at roughly 10–30% of their oils.
Maker's note: Very hard, creamy, long-lasting bar; a vegan tallow substitute. About 8.5% of it is long-chain saturated fat (mostly arachidic, C20:0) that our numbers don't score, so its hardness figure reads a little low.
Calculate lye for Sal butter
The calculator below is pre-loaded with Sal butter. Enter your weights, add other oils, and it works out the exact NaOH (lye) weight, water and quality numbers. Always weigh lye, oils and water — never measure by volume, wear gloves and eye protection, and add lye to water (never the reverse).
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Where these numbers come from
Every figure on this page is backed by at least two independent references, listed below — so you can check our work instead of taking our word for it.
- Biocare — Sal Butter Refined (Certificate of Analysis) — SAP 185–195, iodine 38–44
- PMC (2025) — Shorea robusta seed-oil extraction + characterisation — fatty-acid profile (GC-FID, Table 5): stearic 45.06, oleic 38.23, palmitic 5.95, linoleic 1.95, α-linolenic 0.30, + C17–C22 traces. Its SAP 172.08 is a CRUDE hexane-extracted figure — this row describes refined butter — so it is not used here
- Wikipedia — Shorea robusta seed oil — arachidic 5–8% (the C20:0 share PMC omits); SAP 187–193; iodine 38–42; "used for soap up to 30%"
- Cyberlipid / GERLI — Sal butter — stearic 45–60, palmitic 2–8, oleic 35–50, linoleic 0–8
- LyeCalc — Sal Butter — SAP NaOH 0.130
- Soaper's Choice — SAP Values — SAP (industry consensus)
SAP data last updated · 51 oils covered.
Sal butter soap FAQ
- Can you make soap with 100% Sal butter?
- It is not recommended. Sal butter shows its best in a blend, usually up to about 30% of the oils. On its own the bar would be unbalanced — too soft or low-lathering for everyday use.
- What superfat should I use with Sal butter?
- A 5% superfat is a safe, common starting point for recipes using Sal butter; adjust to taste once you know how the finished bar feels. Never drop to 0% or below without a deliberate reason — the calculator will ask you to confirm it.
- Does Sal butter speed up or slow down trace?
- Because it is rich in palmitic and stearic acids, Sal butter tends to bring a batch to trace quickly and set up fast, so work briskly and keep fragrances that accelerate trace in mind. The upside is a firm bar that usually unmoulds within a day or two.