Rosin
INCI Colophonium. CAS 8050-09-7; EC 232-475-7, as CosIng gives them. Also: Colophony, Colophonium, Gum rosin, Wood rosin, Pine rosin, WW rosin, Water-white rosin, Resin.
Published values
| Saponification value | 165–185 mg KOH/g |
| Used by the calculator | 175.0 mg KOH/g (midpoint) |
| SAP for NaOH | 0.1248 g/g |
| Iodine value | — |
| INS (SAP − IV) | — |
| Melting point | — |
| Unsaponifiable matter | ≤ 6 % |
Soapmaking books print about 0.128 g NaOH per g (median of 2 books). One soapmaking book gives rosin 12-14 % caustic soda by weight, about 0.13 g NaOH per g. Japan's standard for gum rosin sets 165-185 mg KOH/g, and US government data and a 1908 soapmaker's handbook agree, so we use the middle, 175 (0.125). Rosin varies with the pine and the grade, and some Indonesian rosin runs higher, so for more than a few percent of rosin use the figure on your supplier's certificate.
A bar made of 100 % Rosin
The soap qualities are derived from the fatty-acid profile, which is below. They are shown here only for records the calculator can use.
How much lye
| Oil | NaOH | KOH |
|---|---|---|
| 500 g | 59.3 g(55.9–62.6) | 83.1 g(78.4–87.9) |
| 1 kg | 118.5 g(111.7–125.3) | 166.3 g(156.8–175.8) |
| 1 lb (454 g) | 53.8 g(50.7–56.8) | 75.4 g(71.1–79.7) |
| 2 lb (907 g) | 107.5 g(101.4–113.7) | 150.8 g(142.2–159.4) |
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
| Fatty acid | Published range, % | Used | |
|---|---|---|---|
| No fatty-acid profile could be sourced cleanly for this record yet. | |||
Guides that discuss it
Where these numbers come from
Read from the Public.Resource.Org mirror of the Bureau of Indian Standards text. Table 1 gives, per type (extra pale / pale / medium / dark): softening point 70 C min for all; relative density 27/27 C 1.05–1.08, 1.052–1.082, 1.052–1.102; acid number min 160, 155, 155; saponification number min 165, 160, 160; volatile matter max 1.50, 2.0, 2.0 %; ash max 0.05, 0.2, 0.5 %; matter insoluble in toluene max 0.10, 0.40, 1.00 %; unsaponifiable matter max 6.0 % for all. Section 3.2 places the 15 colour grades under those four types, with WW at Gardner colour value 7 under "Pale" — so the pale-type figures are the ones used. Every requirement in the table is a minimum or a maximum; none is a range around a typical value, and the standard prints no typical values.
The source of the saponification value. The standard covers rosin made from raw pine oleoresin (gum rosin). Table 1, grade 1 / grade 2: colour number 1-5 / 1-8; softening point (ring and ball) 75 / 70 C min; acid value 165 / 160 min; saponification value 170-185 / 165-185; unsaponifiable matter 8 / 11 % max; ash 0.02 / 0.05 % max; solvent-insoluble matter 0.05 / 0.1 % max. Read from the page and its table image.
Corroboration. 'The following data have been assembled from sources considered reliable': gum rosin, resin acids and their esters usually 90-95 per cent; acid value 158-172 (the lighter grades usually slightly higher); saponification value 167-184; unsaponifiable matter 5.6-10.7 %; iodine number (Wijs) 205-230. Read from the scan's page images.
Corroboration. 'Typical figures taken from a large number of collated determinations': American W. W. total acid number 169.7 (saponification equivalent 330.5), American N. 179.6, French 175, Spanish 179; free acid numbers 119.1, 161.4, 168 and 160.
Rosin is not a fat. It is what is left after turpentine is distilled off pine oleoresin, and it is roughly nine parts resin acids — abietic and its isomers, C20H30O2 — which are single-carboxyl FREE acids. They neutralise lye directly, one hydroxide per molecule, with no ester to hydrolyse first. That is why IS 553's acid number (155 min for the pale types) and its saponification number (160 min) are almost the same figure, where a triglyceride's acid number is near zero and its saponification number near 200. So rosin soap is a real soap, sodium abietate, and it is what the 19th-century books mean by yellow soap. Six of the transcribed Thomssen and Watt recipes call for it by weight alongside the fats. It lathers freely, it is tacky and soft on its own, and the books keep it under about a quarter of the charge. SAPONIFICATION VALUE is the range Japan's standard for gum rosin, JIS K 5902, prints: 170-185 mg KOH/g for grade 1 (colour numbers 1-5, acid value 165 min, unsaponifiable matter 8 % max) and 165-185 for grade 2 (colour numbers 1-8, acid value 160 min, 11 % max). The record carries the whole 165-185 and the calculator uses its middle, 175. For scale at the top: pure abietic acid is C20H30O2, molar mass 302.45, one carboxyl, so 56106 ÷ 302.45 = 185.5 mg KOH/g, and a rosin that was entirely abietic-type acid could not exceed that. Measured figures agree: the US Southern Regional Research Laboratory's 1952 compilation gives gum rosin 167-184 (acid value 158-172, the lighter grades usually slightly higher), and the 1908 Handbook of Soap Manufacture prints 169.7-179.6 for four commercial grades (American WW and N, French, Spanish). IS 553 sets only minimums, saponification number 165 for extra pale and 160 for pale, medium and dark types, with no ceiling, because a standard's job is to say what a buyer is entitled to; until 2026-09-26 the calculator used that 160 floor, about 9 % under a typical pale gum rosin. Indonesian rosin from Pinus merkusii measures above the band (188.7-194.3 for four Aceh and Jember samples, Sukarno 2018, J. Exp. Life Sci. 8(1):43, Table 2, where Indonesia's SNI 01-5009.12-2001 allows 170-220), and wood rosin and the dark grades can run lower, so for more than a few percent of rosin the saponification number on the supplier's certificate beats any typical figure. No fatty-acid profile is given because rosin has none — resin acids are diterpenes and none of them is in the acids this database records. That means the calculator can work out rosin's lye but not its contribution to hardness, cleansing or conditioning, and a blend containing it will report those qualities over the fats alone. The standard's other requirements, for reference: softening point 70 C min (a softening point, not a melting point, which is why the melting-point field is blank), relative density 1.052–1.082 at 27/27 C for the pale type, volatile matter 2.0 % max, ash 0.2 % max, matter insoluble in toluene 0.40 % max.
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.