The soaping oils: what each one brings to a bar

In short

An oil's fatty acids decide what it does: lauric and myristic clean and lather, palmitic and stearic harden, oleic conditions, ricinoleic steadies the lather, and linoleic and linolenic condition but go rancid first.
The usual shares given here are craft conventions from soapmaking books, not rules. Once the lye is calculated, any saponifiable oil makes safe soap at any share.
Names can hide different oils: high-oleic and standard sunflower share one ingredient name but keep very differently in soap.
Jojoba and beeswax are waxes. They saponify slowly and only in part, so in soap they behave as additives.
Neem and avocado oil have wide published saponification values, and the standards for unrefined shea allow a wide band too. At a large share, give the recipe a point or two of extra superfat or use the value on your lot's certificate.

On this page

A soap recipe is a list of oils, and each one is there for the fatty acids it brings. Coconut oil is in most bars for its lauric acid, olive oil for its oleic acid, castor for the ricinoleic acid that no other common oil carries. This page goes through the twenty-five oils, butters and waxes you are most likely to meet: what each does to a bar and why, the share makers usually give it, and what to watch for. Every figure comes from the records the calculator uses, and each oil links to its own page in the oil database, where the published ranges and the documents they were read from are set out. To put two oils side by side, open the oil comparison.

How to read the entries

Each entry names the oil’s main fatty acids, gives its saponification (SAP) value as the published range, and says what the oil does in a blend, the share makers usually give it, and anything to watch for. Where it helps, it also gives what a bar made from that oil alone scores on the five soap qualities, which is what the oil’s own page shows. The table also gives each oil’s iodine value, a laboratory measure of its double bonds: the higher it is, the softer the soap and the sooner its free oil can turn rancid (see iodine value and INS).

The fatty acids do the work

The eight fatty acids the soap qualities are built from, and the qualities each counts toward. The rest of this page is these acids, in different proportions.

Lauric and myristic acid are short saturated chains of 12 and 14 carbons. Their soaps dissolve readily (Failor), so they lather at once with big bubbles and clean strongly, and they also make the bar firm. That same readiness to dissolve is why a bar with a lot of them can leave skin feeling tight. Coconut, palm kernel and babassu oil are the lauric oils.

Palmitic and stearic acid are longer saturated chains, 16 and 18 carbons, straight enough to pack tightly. They give a hard bar that wears slowly and a small, dense, stable lather. Palm oil, the animal fats and the butters carry them.

Oleic acid has 18 carbons and one double bond, which puts a bend in the chain. Its soap is mild and conditioning but starts soft and firms slowly, with a low, slippery lather. Olive oil is mostly oleic acid.

Linoleic and linolenic acid have two and three double bonds. The convention counts them as conditioning, but each double bond is also a place for oxygen to attack, and a chain with two double bonds oxidises roughly 10 to 40 times faster than one with a single double bond (Gharby et al., 2025). These are the acids behind rancid soap and orange spots, and not only in the free oil the superfat leaves: Dunn’s olive oil soap with no superfat turned orange as soon as one with 10 %.

Ricinoleic acid is oleic acid with a hydroxyl group partway along, and castor oil is about nine-tenths of it. The hydroxyl makes its soap unusually soluble: a small amount steadies and thickens the lather, and a lot makes a soft, sticky bar.

The small part of an oil that lye cannot turn into soap is its unsaponifiable matter (sterols, vitamins, hydrocarbons, waxy alcohols), and it passes through the reaction untouched. Most oils carry a percent or two; shea butter, rice bran oil and jojoba carry far more, and it shows in how they behave.

The shares given here are craft conventions: what experienced makers, and the books they write, settled on for an everyday bar that is hard enough to last, lathers well, cures in weeks and keeps well. They are not safety limits. Once the lye is calculated, any oil that saponifies makes safe soap at any share, and some classics sit far outside the ranges: a salt bar is mostly coconut oil, and a shaving soap can be 40 % stearic acid. Where a range comes from a particular book, the book is named, and where books disagree, both are given. The five quality numbers are a convention too, a way of adding up fatty acids that the fatty acids guide takes apart; they call castile too soft, and castile is one of the oldest soaps there is.

The oils at a glance

Oil	Main fatty acids, %	SAP, mg KOH/g	NaOH per 100 g	Iodine value	Usual share
Olive	oleic 69, palmitic 14, linoleic 12	184–196	13.5 g	75–94	up to 100 %
Coconut	lauric 49, myristic 19, palmitic 9	248–265	18.3 g	6.3–10.6	15–30 %
Palm kernel	lauric 50, myristic 16, oleic 16	230–254	17.3 g	14.1–21	up to 15 %
Babassu	lauric 48, myristic 19, oleic 15	245–256	17.9 g	10–18	as coconut
Palm	palmitic 43, oleic 40, linoleic 11	190–209	14.2 g	50–55	up to 25–30 %
Lard	oleic 45, palmitic 25, stearic 15	192–203	14.1 g	55–65	up to 100 %
Tallow	oleic 38, palmitic 25, stearic 23	190–202	14.0 g	40–53	up to 100 %
Shea butter	oleic 47, stearic 42, linoleic 6	179.3–190	13.0 g	30–75	5–15 %
Cocoa butter	oleic 35, stearic 34, palmitic 27	188–198	13.8 g	33–42	up to 15 %
Mango butter	stearic 43, oleic 43, palmitic 6	185–198	13.7 g	32–57	up to 15 %
Kokum butter	stearic 52, oleic 42	187–191.7	13.5 g	32–40	none published
Castor	ricinoleic 89	176–182	12.8 g	83–88	3–8 %
Sweet almond	oleic 69, linoleic 25	183–207	13.9 g	85–109	up to 25 %
Apricot kernel	oleic 62, linoleic 28	185–195	13.5 g	90–115	up to 10–15 %
Avocado	oleic 62, palmitic 15, linoleic 13	170–202	13.3 g	75–95	up to 20 %
Sunflower, high-oleic	oleic 83, linoleic 10	182–194	13.4 g	78–90	as olive
Sunflower, standard	linoleic 61, oleic 27	188–194	13.6 g	118–141	up to 20 %
Canola	oleic 61, linoleic 23, linolenic 10	182–193	13.4 g	105–126	up to 35 %
Rice bran	oleic 43, linoleic 32, palmitic 19	180–199	13.5 g	90–115	5–50 %
Hemp seed	linoleic 55, linolenic 22, oleic 13	none published	13.7 g	145–170	up to 20 %, often 5 %
Jojoba	gadoleic 72, erucic 14 (as wax esters)	93	6.6 g	81–94.8	up to 10 %
Beeswax	wax esters; no profile published	87–104	6.8 g	not published	0.5–2 %
Stearic acid	stearic 52, palmitic 47	206–212	14.9 g	0.5 or less	0.5 % in bars
Laurel berry	oleic 37, linoleic 23, lauric 19	198–199	14.2 g	68–80	set by price
Neem	oleic 41, palmitic 18, linoleic 19	175–205	13.5 g	74.9–150	around 5–10 %

Fatty acids are the representative values the calculator uses; SAP and iodine values are the published ranges on each oil’s page. NaOH per 100 g is the lye that saponifies 100 g of the oil completely at the value the calculator uses, before any superfat. “Usual share” is a craft convention for an everyday cold process bar; each entry below says where it comes from.

The lauric oils: coconut, palm kernel and babassu

Coconut oil

Coconut oil is about half lauric acid (45.1–53.2 %) and a fifth myristic (16.8–21 %), with small amounts of the shorter caprylic and capric acids. Those short chains make a hard, white bar that lathers fast in big, airy bubbles and cleans very well. On its own it scores 80 for hardness and 68 for cleansing, far above the convention’s bands. Short chains also mean more molecules per gram, so coconut oil needs more lye than any other oil here: 18.3 g of sodium hydroxide per 100 g, a third more than olive oil.

Usual share: 15–30 %. Faiola says some people find it drying above 25 % and generally keeps it to 35 % or less; Fisher puts the usual ceiling at about 30 % unless the superfat goes up. The exception is the salt bar, which is mostly coconut at a high superfat (see the salt bar guide and the pink salt spa bar, 70 % coconut at an 18 % superfat).

Watch for: the grade. Ordinary coconut oil melts at 23–26 °C, which is why it is sold as “76-degree” in the United States. Fractionated coconut oil is a different product (mostly caprylic and capric acid, SAP 310–360) and needs far more lye: in a 70/30 olive and coconut bar, putting fractionated oil in place of ordinary coconut oil takes the lye from 142.2 g to 158.1 g per 1000 g of oils. Never swap one for the other without recalculating. Coconut oil in the database.

Palm kernel oil

Pressed from the kernel of the oil palm rather than the fruit, palm kernel oil is a lauric oil like coconut: lauric 45–55 %, myristic 14–18 %, with a little more oleic acid (12–19 %). It behaves like coconut in soap (Fisher; Failor), giving a hard bar and a quick, bubbly lather.

Usual share: up to 15 % (Faiola, who finds it brittle and quick to trace), though Watson’s olive and palm kernel bars use it at 40 % in coconut’s place. Cavitch found 10 to 15 % plenty, and that more let the bars take on the oil’s own smell.

Watch for: it needs less lye than coconut oil. In the same 70/30 olive bar, palm kernel oil takes 139.2 g of sodium hydroxide where coconut takes 142.2 g, so the two are not interchangeable without recalculating. It carries the same sustainability questions as palm oil (see palm-free soap). Palm kernel oil in the database.

Babassu oil

From the nut of a Brazilian palm, babassu is lauric 40–55 %, myristic 11–27 %, oleic 9–20 %. Cable uses it in place of coconut oil, at 18–29 % in her recipes, and finds it gentler; on the numbers the difference is small, since a babassu bar and a coconut bar of the same recipe score within about three points of each other. Cable suggests it for anyone avoiding coconut.

Usual share: as coconut oil, 15–30 %.

Watch for: Cable finds it speeds trace. It needs 17.9 g of sodium hydroxide per 100 g against coconut’s 18.3 g, so recalculate after a swap. Babassu oil in the database.

Palm oil and the animal fats

Palm oil

Palm oil is pressed from the fruit pulp of the oil palm and is close to half palmitic acid (39.3–47.5 %) and two-fifths oleic (36–44 %). That balance of hard and soft makes a firm, long-lasting, mild bar with a stable, creamy lather (Fisher; Letcavage and Harden), which is why it anchors the classic olive, coconut and palm recipe. A bar of palm alone scores 50 for hardness and 48 for creamy lather.

Usual share: up to 25 % (Faiola); the classic olive, coconut and palm bar uses 30 %. Older soaps used far more: toilet soap bases of a century ago were three-quarters or more palm or tallow (see Thomssen’s palm base).

Watch for: its fractions separate in the tub, with the harder, palmitic-rich part settling out, so melt and stir the whole container before you weigh any (Faiola; Failor). It also speeds trace, pulling the other oils along, so scent and additives have to go in quickly (Cavitch). Unbleached “red” palm oil carries 500 to 2,000 mg/kg of carotenoids, the pigments that make it orange, and tints the soap. The environmental case against it is set out in palm-free soap. Palm oil in the database.

Lard

Lard is rendered pig fat: oleic 35–55 %, palmitic 20–30 %, stearic 8–22 %, linoleic 4–12 %. It makes a hard, white, mild bar with a creamy, low lather, and it is cheap. A lard bar scores 42 for hardness and 55 for conditioning; lard is a little softer than palm oil, with fewer hard acids and more oleic.

Usual share: up to 100 %; blends commonly run 25–50 % (Cable’s recipes use 24–38 %). The old-fashioned lard bar is 80 % lard and 20 % coconut.

Watch for: supermarket lard. Fisher notes that it is usually partially hydrogenated to keep longer, which changes its fatty acids, and the Codex standard allows antioxidants such as BHT to be added. At the other end, inedible lard sold as “choice white grease” is much higher in free fatty acids and often chemically preserved, and low grades develop a lardy smell in the bar (Cavitch). Check the label, and see the lard and tallow guide for rendering your own. Lard in the database.

Tallow

Tallow is rendered beef or mutton fat: oleic 30–45 %, palmitic 20–30 %, stearic 15–30 %, and only 1–6 % linoleic. More stearic acid and less linoleic than lard make it harder (52 on its own) and slow to go rancid. Its lather is small and stable, which is why it is usually paired with a lauric oil.

Usual share: up to 100 % (Faiola); the classic farmhouse bar is three parts tallow to one of coconut (kitchen tallow bar), and the creamy tallow and olive bar uses 50 %.

Watch for: the quality of the rendering, which decides whether the soap smells of anything. The lard and tallow guide covers it. Tallow in the database.

The butters: shea, cocoa, mango and kokum

Shea butter

Shea butter is oleic 34–60.7 % and stearic 27.7–55.7 %, ranges so wide because they come from 36 samples across seven African countries (Akihisa et al., 2010). Its stearic acid makes it a hardener; its oleic acid keeps the bar mild. It is also unusually rich in unsaponifiable matter, 2.4–11.6 % in the same study, and that material passes into the bar unchanged; makers credit it for shea’s conditioning feel (Letcavage and Harden).

Usual share: 5–15 %. Faiola keeps it to 10 % or less; Cable’s recipes use 3–16 %; Corley Barto builds most of hers on 30 %, as does our shea and cocoa butter luxury bar; and our palm-free recipe uses 20 % to replace palm’s hardness.

Watch for: its SAP value. The standards for unrefined shea allow 160–195 mg KOH/g (Codex) or 160–200 (India), because they cover butters with up to 19 % unsaponifiable matter. Butters that have been measured fall between 179.3 and 190, and the calculator uses 183, the value for a refined shea. A crude butter rich in unsaponifiables needs less lye than that, so at a large share add a point or two of superfat or use the value on your supplier’s certificate. Shea butter in the database.

Cocoa butter

Cocoa butter is an even three-way split: palmitic 23–30 %, stearic 31–37 %, oleic 31–38 %. Nearly two-thirds saturated, it is the hardest of the common butters (61 for hardness on its own) and gives a small, stable lather. It melts at 31–35 °C.

Usual share: up to 15 %. Faiola finds that more can contribute to cracking, and cocoa butter-heavy bars can be brittle.

Watch for: the scent. Unrefined cocoa butter smells of chocolate and the smell carries into the bar (Letcavage and Harden; Fisher), so buy deodorised if you want a neutral base. Cocoa butter in the database.

Mango butter

Mango kernel fat is stearic and oleic acid in roughly equal parts, 35–50 % each, with a little palmitic: close to shea in make-up and softer than cocoa butter. Faiola finds it adds conditioning without much lather or hardness.

Usual share: up to 15 % (Faiola); Cable’s recipes use 6–19 %.

Watch for: the variety. Four Ivorian mango butters melted anywhere from 17.6 to 34.3 °C (Diomande et al.), so one lot can be much softer than the next. The fatty acids here are a refiner’s specification (Heess), in line with the Indian standard for mango kernel fat, whose SAP range, 185–198, the calculator uses. Mango butter in the database.

Kokum butter

Kokum, from the seed of an Indian fruit tree, is about half stearic acid (52 %) and two-fifths oleic (41.5 %) in the one full analysis available, a 1939 study. That makes it a hard, brittle butter much like cocoa butter in soap (59 for hardness on its own), without the chocolate smell.

Usual share: none of the books we trust gives one. Its make-up is close to cocoa butter’s, so the same caution about brittleness applies, and treating it the same way, up to about 15 %, is our suggestion rather than a published convention.

Watch for: the thin data. Its SAP value (187–191.7) comes from Indian food standards; its fatty acids are a single old analysis. Kokum butter in the database.

Castor oil

Castor oil is 85–92 % ricinoleic acid, a fatty acid no other common oil carries in quantity. The hydroxyl group on its chain makes castor soap very soluble in water, so a small share steadies and thickens the lather of the whole bar; a large share makes the bar soft and tacky. On its own it scores 89 for bubbly lather, 93 for creamy and only 5 for hardness.

Usual share: 3–8 %. Faiola finds 3–5 % gives the best lather and above 10 % a soft bar; Fisher warns of a soft, rubbery soap above about 8 %. Shampoo bars, liquid soap and transparent soap use more, the last up to a third of the oils (Failor), where castor’s solvent-like soap helps clarity.

Watch for: the quality numbers do not show the problem. Raising castor from 5 % to 15 % in an olive and coconut bar lifts bubbly lather from 25 to 34 and barely moves hardness (35 to 34), yet the second bar is the stickier one. Castor also speeds trace (Fisher; Cable). Castor oil in the database.

Watch castor work. This olive and coconut bar with 5 % castor needs 141.8 g of sodium hydroxide per 1000 g of oils at a 5 % superfat. Change castor to 15 % and see which numbers move.

Open it in the calculator

Olive and the other oleic oils

Olive oil

Olive oil is oleic 55–83 %, palmitic 7.5–20 %, linoleic 3.5–21 %. Its soap is very mild, with a low, slippery lather, and starts soft: a bar of olive oil alone scores 17 for hardness, yet a well-cured castile ends up very hard (Fisher), and the long cure is part of the recipe. The castile soap guide explains why the numbers undersell it.

Usual share: anything up to 100 % (Faiola; Fisher), which is castile; the high-olive bastile bar keeps 75 % and adds coconut and castor for lather.

Watch for: the grade matters less to the finished bar than people think; freshness matters more (Fisher). It does change the working time. Pomace oil, the last extraction from the paste, may carry up to 3 % unsaponifiable matter against 1.5 % for other grades, and it traces fastest: Cavitch’s hand-stirred olive recipes traced in anywhere from 7 to 40 minutes depending on the grade, pomace quickest (and darkest), extra virgin slowest. Faiola uses that as a dial, pomace for layers and textured tops that should set up sooner, extra virgin for long swirls (Pure Soapmaking). Green virgin oils tint the bar; for a white one, Cavitch chose a refined oil that looks bright yellow in the bottle. The wide linoleic range (up to 21 %) means some olive oils keep better than others. Olive oil in the database.

Sweet almond oil

Oleic 62–76 %, linoleic 20–30 %. A soft, conditioning oil with a stable, low lather, used for feel.

Usual share: up to 25 % (Faiola).

Watch for: the linoleic acid, a quarter of the oil, which shortens shelf life at high shares. It is a nut oil, and its ingredient name (Prunus Amygdalus Dulcis Oil, or Sodium Almondate once saponified) tells an allergic customer so. Sweet almond oil in the database.

Apricot kernel oil

Oleic 54–70 %, linoleic 20–35 %, much like sweet almond oil, and used the same way.

Usual share: up to 15 % (Faiola), 10 % (Cable). Both find more gives a soft bar that does not hold up in the shower.

Watch for: as almond, the linoleic acid. Apricot kernel oil in the database.

Avocado oil

Oleic 50–74 %, palmitic 5–25 %, linoleic 6–20 %, with more palmitoleic acid (1–12 %) than most oils. It behaves much like olive oil with a little more palmitic acid, and makers use it for a rich, conditioning feel.

Usual share: up to 20 % (Faiola).

Watch for: a wide SAP range. Codex gives crude avocado oil 170–202 mg KOH/g, and the calculator uses the middle, 186. Unrefined avocado oil carries more unsaponifiable matter than most oils (Fisher), which pulls its value down; a refined oil, with at most 2 %, sits in the upper half. At a large share, a point of extra superfat covers the spread. The rice bran and avocado bar uses 25 %. Avocado oil in the database.

Sunflower oil, high-oleic

High-oleic sunflower oil must be at least 75 % oleic acid by the Codex standard (75–90.7 %), with linoleic 2.1–17 %. In soap it behaves like a pale olive oil and keeps well.

Usual share: as olive oil. Faiola suggests 20 % or less for sunflower oils, citing a soft bar and a short shelf life; the high-oleic kind keeps far better, and our recipes use it at 5–30 %.

Watch for: the label. Both kinds carry the same ingredient name, Helianthus Annuus Seed Oil, so only the supplier’s specification tells you which you have. High-oleic sunflower oil in the database.

Canola oil

Low-erucic rapeseed oil: oleic 51–70 %, linoleic 15–30 %, linolenic 5–14 %. Cheap, pale and mild, with a creamy lather. Faiola finds it slows trace, which gives time for swirls, and makes a whiter bar than olive oil.

Usual share: up to 35 % (Faiola), or 40 % in her Pure Soapmaking, which prefers the high-oleic kind because it goes rancid less quickly; our budget bar uses 25 % and the supermarket oils bar 15 %.

Watch for: the linolenic acid, up to 14 %, the fastest-oxidising of the common acids. Faiola notes that some makers blame canola for orange spots. A high-oleic canola exists with about 2.5 % linolenic acid. Canola oil in the database.

Rice bran oil

Oleic 38–48 %, linoleic 21–42 %, palmitic 14–23 %. Its palmitic acid puts it among the heavier liquid oils (Fisher), and it carries up to 6.5 % unsaponifiable matter, including 0.9–2.1 % gamma-oryzanol in the crude oil.

Usual share: Faiola rates it usable up to 100 % and uses 7–50 % in her recipes; ours use 5–30 %, the most in the rice bran and avocado bar. Faiola and Grosso both suggest it in place of olive oil to cut the cost.

Watch for: the linoleic acid, up to 42 % in some oils. Rice bran oil in the database.

The polyunsaturated oils: standard sunflower and hemp seed

Sunflower oil, standard

Ordinary sunflower oil is the opposite of the high-oleic kind: linoleic 48.3–74 %, oleic 14–39.4 %. The five quality numbers barely tell the two apart (in a 70/30 bar with coconut, hardness 32 against 30 and conditioning 64 against 68), but the iodine value does: 93 for the standard oil’s bar against 61 for the high-oleic. That iodine value is the linoleic acid, and it is why the standard oil keeps poorly in soap.

Usual share: up to 20 % (Faiola), and less is safer for a bar meant to keep.

Watch for: the same goes for grapeseed (linoleic 58–78 %) and soybean oil (linoleic 48–59 %, linolenic 4.5–11 %). Keep them to a small share, buy them fresh and cure the soap somewhere cool. Standard sunflower oil in the database.

Hemp seed oil

The most unsaturated oil here: linoleic 44.5–65.5 %, alpha-linolenic 13.5–30.5 %, iodine value 145–170. Cable uses it for the silky feel it gives a bar.

Usual share: Faiola allows up to 20 %; the recipes in the books we checked use 4–6 %.

Watch for: rancidity. Cable finds it oxidises sooner than other oils in soap and advises using hemp soap within six months, or keeping the superfat down to about 5 %. The oil itself keeps three to six months unrefined and about a year refined (Faiola, Pure Soapmaking), so buy it fresh. There is no published SAP value; the calculator uses 192.2, worked out from its fatty acids. Hemp seed oil in the database.

Waxes and a fatty acid: jojoba, beeswax and stearic acid

Jojoba

Jojoba “oil” is a liquid wax. About 97 % of it is wax esters, each a long monounsaturated fatty acid (gadoleic acid, 67.9–75.5 % of the acids, and erucic) joined to a long fatty alcohol rather than to glycerol. That has three consequences. Its SAP value is about 93 mg KOH/g, half that of an ordinary oil. Wax esters saponify slowly, so under soapmaking conditions much of the jojoba stays as it is and acts as extra superfat. And even complete saponification would leave about half its weight as fatty alcohols, which do not become soap: the Cosmetic Ingredient Review puts its unsaponifiable matter at 51 %.

Usual share: up to 10 %. Faiola finds more weighs the lather down; Cable keeps it below 15 %.

Watch for: the quality numbers are meaningless for it: they do not count gadoleic or erucic acid, so a jojoba bar scores 12 for conditioning. The calculator gives it lye at 93, so if it saponifies less than that, the bar ends up with more superfat than stated, never less. Jojoba in the database.

Beeswax

Beeswax is also a wax, esters of very long alcohols with some free fatty acids and hydrocarbons, melting at 62–65 °C. Only its free acids react readily with lye; the esters saponify slowly, so it contributes little soap and works mainly as a hardener. Its SAP value is 87–104 mg KOH/g.

Usual share: up to 2 % of the oils (Faiola), who also uses 0.5 % at trace against soda ash; her Pure Soapmaking allows 3 %, soaped at 63 °C (145 °F) or above so the wax does not set, and warns that too much cuts the lather.

Watch for: it thickens batter fast. Faiola melts it separately and hand-stirs it in at thin trace, with the batter at 60 °C (140 °F) or above, because cooler batter sets it into small lumps. The honey and beeswax bar stirs it into oils held at 50–55 °C instead and stops blending at light trace. No fatty-acid profile is published for it, so it scores zero on every quality, which means nothing. It is not vegan. Beeswax in the database.

Stearic acid

The stearic acid soapmakers buy is a triple-pressed mixture of stearic (50–54 %) and palmitic acid (45–49 %), made from palm oil or animal fat (Faiola; Failor). Being a free fatty acid rather than a fat, it does not saponify: lye neutralises it at once, making soap and water and no glycerin. That speed explains how it behaves. It hardens a bar and brings trace on fast, and if it sits in the oils when the lye goes in, the batter can thicken past stirring or curdle.

Usual share: 0.5 % as a hardener in ordinary bars (Faiola). Transparent soap uses 7–20 % (Failor), and shaving and cream soaps make it a main fat: 40 % in our shaving soap, 45 % in the hot-process stearic shaving soap and 30 % in our cream soap.

Watch for: the method. Failor melts it separately and adds it after the other oils have traced; Faiola adds it melted at thin trace, to batter at 57 °C (135 °F) or above. For makers avoiding palm oil, note that stearic acid is often palm-derived. Stearic acid in the database.

Two specialists: laurel berry and neem

Laurel berry oil

Pressed from the fruit of the bay laurel, this is the oil of Aleppo soap: oleic 22.1–44.4 %, linoleic 15.9–26.8 %, lauric 12.7–31.2 % and palmitic 12.4–19.9 % across three analyses, with about 1 % unsaponifiable matter and a few percent of volatile oil that give it its scent. Its lauric acid gives it some of coconut oil’s cleansing and lather, which olive oil lacks.

Usual share: price sets it. Aleppo soap is graded by its laurel share; our Aleppo recipe uses 20 %, a common middle grade, and the Aleppo-style laurel bar 25 %. The Aleppo soap guide covers the range.

Watch for: three things. Lauric acid varies from tree to tree, from 13 to 31 % across 48 Turkish genotypes (Ayanoğlu et al., 2018), so read its quality scores as a range. It is not bay laurel essential oil, a leaf distillate that makes no soap and that IFRA limits to about 0.053 % of a finished soap (see scenting soap). And California adds oil from bay laurel seeds to the ingredients cosmetics may not contain from 1 January 2027; the regulatory calendar has the detail, and your supplier can tell you what your oil is pressed from. Laurel berry oil in the database.

Neem oil

Neem seed oil is roughly oleic 28–41 %, palmitic 12–19 %, stearic 4–15 % and linoleic 19–46 %, a moderately hard oil whose make-up varies a great deal with how it was extracted. Makers add it for its traditional reputation.

Usual share: small. Cable’s one neem recipe uses 6 %; our dog bar uses 10 %.

Watch for: its SAP value. The Indian standard for neem oil allows 175–205 mg KOH/g, and the calculator uses the middle, 190; one study measured 159.7 to 194.6 from the same seed with four different solvents. At more than a few percent, give the recipe a point or two of extra superfat. Its linoleic acid, up to 46 % in one commercial sample, shortens shelf life. And make no treatment claims for it: they change how the soap is regulated (see labelling soap). Neem oil in the database.

Swapping one oil for another

Swap within a family and the bar changes least: lard or tallow for palm, babassu or palm kernel for coconut, high-oleic sunflower or rice bran for some of the olive. Every swap changes the lye, even between close relatives, so run the new recipe through the calculator before you weigh anything: coconut, palm kernel and babassu differ by up to 3.0 g of sodium hydroxide per 1000 g of oils in the same 70/30 olive bar, and fractionated coconut oil by 15.9 g. The compare tool shows two oils’ fatty acids side by side, and designing a soap recipe shows how to build a blend from them.

Try a swap. A bar of 70 % olive and 30 % coconut oil needs 142.2 g of sodium hydroxide per 1000 g of oils at a 5 % superfat. Swap the coconut for babassu or palm kernel oil and watch the lye and the numbers change.