Stearic Acid (triple-pressed, ~50:50 C16/C18)
INCI Stearic Acid. Saponified with NaOH it is listed as Sodium Stearate, with KOH as Potassium Stearate. CAS 57-11-4; EC 200-313-4, as CosIng gives them. Also: Octadecanoic acid (commercial), Stearic acid 50%, Triple pressed stearic acid, Stearic acid NF, Palm stearic acid.
Published values
| Saponification value | 206–212 mg KOH/g |
| Used by the calculator | 209.0 mg KOH/g (midpoint) |
| SAP for NaOH | 0.1490 g/g |
| Iodine value | ≤ 0.5 g I₂/100 g |
| INS (SAP − IV) | 209 |
| Melting point | — |
| Unsaponifiable matter | — |
Soapmaking books print about 0.144 g NaOH per g (median of 2 books). Books print 0.140-0.147 g NaOH per g for stearic acid, and the difference is the grade. 0.140 is nearly pure stearic acid; the triple-pressed stearic acid soapmakers usually buy is about half palmitic acid and takes 206-212 mg KOH/g, so we use 209 (0.149).
A bar made of 100 % Stearic Acid
Conventional qualities summed from the fatty-acid groups; a single-oil bar is a reference point, not a recipe.
How much lye
| Oil | NaOH | KOH |
|---|---|---|
| 500 g | 70.8 g(69.8–71.8) | 99.3 g(97.9–100.7) |
| 1 kg | 141.5 g(139.5–143.6) | 198.6 g(195.7–201.4) |
| 1 lb (454 g) | 64.2 g(63.3–65.1) | 90.1 g(88.8–91.4) |
| 2 lb (907 g) | 128.4 g(126.6–130.3) | 180.1 g(177.5–182.7) |
For this oil alone at 5 % superfat, with pure sodium hydroxide (NaOH) or pure potassium hydroxide (KOH); in brackets, across the published range of its saponification value. KOH is usually sold at 90 %: divide by 0.9. For a whole recipe, open the calculator.
Fatty-acid profile
Saturated : unsaturated 98 : 2
| Fatty acid | Published range, % | Used | |
|---|---|---|---|
| Myristic acid | C14:0 · saturated | ≤ 2 | 2.0 |
| Palmitic acid | C16:0 · saturated | 45–49 | 47.0 |
| Stearic acid | C18:0 · saturated | 50–54 | 52.0 |
| Oleic acid | C18:1 | ≤ 0.5 | 0.5 |
| Linoleic acid | C18:2 | ≤ 1.5 | 1.5 |
Recipes that use it
- Shaving croap 50 % of the oils
- Stearic acid shaving soap 45 % of the oils
- Shaving soap 40 % of the oils
- Cream soap 30 % of the oils
- Whipped cream soap 25 % of the oils
Guides that discuss it
Where these numbers come from
Specification table on the product page: acid value, saponification value, iodine value, titre, colour, C14/C16/C18/C18:1/C18:2 composition limits.
EMERSOL 132 NF row: acid value 205-211 mg KOH/g, iodine value 0.5 max, titer 54.5-55.5 C; EMERSOL 120 (double pressed): acid value 205-210, iodine value 5-7, titer 53.7-54.7 C, C16 38-44 %, C18 43-48 %.
Brochure PDF (uploaded 2012) used only for the grade comparison in notes; its text-extracted table rows are offset by one line, so the product page is the authoritative source for SA-1850.
Commercial 'stearic acid' used in soap is a palmitic/stearic mixture, not pure C18. Primary values are the producer specification for Wilmar WILFARIN SA-1850 (Stearic Acid 50 %, triple pressed): acid value 205-211 mg KOH/g, saponification value 206-212 mg KOH/g, iodine value 0.5 max (% I2 absorbed = g/100 g), titre 55-57 C, colour 0.3/3 max (Lovibond R/Y), composition C14 2 % max, C16 45-49 %, C18 50-54 %, C18:1 0.5 % max, C18:2 1.5 % max. Emery Oleochemicals' EMERSOL 132 NF (triple-pressed tallow stearic acid) has matching limits: acid value 205-211 mg KOH/g, iodine value 0.5 max, titer 54.5-55.5 C (additional source; Emery's page gives no SAP). Free fatty acid: SAP is essentially the acid value; use directly for lye calculation. Titre is a solidification point, so the melting point is blank. Other grades differ (Wilmar brochure: SA-1892 92 % stearic AV ~195-199/SAP ~196-200, titre 66-70 C; SA-1865 65 % AV ~202-209; rubber grades SA-1810/1804 AV >= 195 with IV up to 4-10) - see notes if modelling a 90 %+ C18 grade. INCI and salt names are the standard CosIng entries, not re-verified on CosIng in this session.
This record is part of the open ingredient database (ODbL), which you can download as CSV or JSON. Found an error or a better primary source? Corrections with a link to the document are welcome at support@soapformulator.com.