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Traditional

African black soap homage

Pale honey-coloured balls of soft, glossy potassium soap, one pinched open, beside small dishes of shea butter and palm kernel oil on a deep indigo blue backdrop

An honest homage to West African black soap: palm kernel oil, coconut oil and shea butter cooked with potassium hydroxide into a soft, pliable soap you pinch off and lather in your hands. The ash lye and dark colour of the original are not reproduced, so this one is pale and smooth, with a big, rich lather.

Skill
Advanced
Method
Hot process
Batch
500 g of oils about 1070 g of batter
Hands-on
1 h 30 min
Cure
2 weeks
Gel phase
In the pot it gels as it cooks
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What you need

For 500 g of oils, which fills a 1.2 litre tub lined with baking paper, or hand-rolled balls. Weigh everything, liquids included.

Palm Kernel Oil · 45.0 % 225 g 7.94 oz
Coconut Oil · 25.0 % 125 g 4.41 oz
Shea Butter · 30.0 % 150 g 5.29 oz
Potassium hydroxide (KOH) · the lye, 90 % pure; if your label says otherwise, weigh 126.8 g at 85 % or 113.4 g at 95 % 119.7 g 4.22 oz
Distilled water · for a 21 % lye solution 450.0 g 15.87 oz
Superfat
6 %
Temperatures
Lye solution cooled below 82 °C (180 °F), fats at 65 to 71 °C (150 to 160 °F), cooked on low

Resize or change it in the calculator

Method

  1. Get ready

    Put on sealed goggles, nitrile gloves and long sleeves, and keep them on until the soap is cooked and cooled. Weigh 225 g palm kernel oil, 125 g coconut oil and 150 g shea butter into a slow cooker of 3.5 litres or more, 450 g distilled water into a heat-proof jug and 119.7 g potassium hydroxide flakes into a dry container, then close the flake tub at once: it pulls water from the air.

  2. Make the lye solution

    At an open window, add the flakes to the water a little at a time, stirring, never the water to the flakes. It fizzes and gets hotter than sodium hydroxide does; let it cool below 82 °C (180 °F), and keep it away from aluminium, tin and zinc, which it attacks, giving off hydrogen.

  3. Melt the fats

    Melt the palm kernel oil, coconut oil and shea butter in the slow cooker on low and bring them to 65 to 71 °C (150 to 160 °F).

  4. Blend to a paste

    Pour the lye solution into the fats and stick blend in bursts of a minute or so, stirring between them. With this much water the batter is thin at first, then thickens quickly as the palm kernel and coconut oils react; keep going until it is an even, opaque paste like soft mashed potato.

  5. Cover and cook

    Put the lid on and leave the cooker on low, and stay nearby for the first half hour: soap this rich in coconut and palm kernel oil can foam up the sides of the pot. Stir it down whenever it rises, then stir every 20 to 30 minutes.

  6. Cook until even

    Over two to three hours the paste turns from chalky white to a glossy, slightly translucent cream or pale honey colour, with the feel of petroleum jelly. It never turns fully clear: the superfat and shea keep it cloudy.

  7. Test a spoonful

    Stir a teaspoon of the soap into half a cup of boiling distilled water until it dissolves and let it cool. A cloudy liquid is what you want; a greasy film or droplets on top mean some oil has not reacted yet, so cook another half hour and test again.

  8. Cook off some water

    Take the lid off and keep the cooker on low for 30 to 60 minutes, folding the soap over every few minutes, until it is a thick, sticky dough that pulls away from the sides. Driving off steam lets it firm up sooner; the recipe itself does not change.

  9. Shape it

    Turn off the cooker. When the soap is cool enough to handle in gloves but still soft, press it into the lined tub, or roll it into balls of about 100 g; lightly dampened gloves stop it sticking.

  10. Clean up

    Scrape the pot and tools with paper towels into the bin, then soak them in hot water, which dissolves potassium soap easily, and wash them.

  11. Let it firm up

    Leave the soap uncovered on a rack for two to four weeks, turning the balls or the block now and then, until it holds its shape and no longer feels tacky. It stays softer and more pliable than a bar made with sodium hydroxide: that is the nature of potassium soap, and of black soap.

  12. Store and use it

    Keep it wrapped or in a lidded tin, because potassium soap draws moisture from the air and turns sticky in a steamy bathroom. Pinch off a piece and work it into a lather between wet hands or on a cloth, and put the rest away dry.

Tips

  • The ash is the whole difference. Traditional makers roast plantain skins, cocoa pods or palm leaves, leach the ash for its potash and cook it with the oils, and the roasting colours the soap brown to black and leaves the bits that make it rough and crumbly. Weighed potassium hydroxide gives a pale, smooth soap with a known superfat, so this is a homage and not a copy; cocoa powder or charcoal would darken it but would not make it black soap.
  • The lye assumes potassium hydroxide flakes of 90 % purity, the usual label figure. If your label says otherwise, enter it in the calculator before you weigh: purer flakes make the soap lye-heavy.
  • The calculator shows a warning that liquid soap is usually made at 0 to 3 % superfat. That is about clouding soap that is diluted into a liquid; this one is never diluted, and the 6 % superfat is chosen to soften a soap this high in coconut and palm kernel oil.
  • Shea is botanically a tree nut. Refined shea butter carries almost no protein, but anyone with a nut allergy should read our nut-free bar first.

Why make it

Black soap, ose dudu in Yoruba, is an everyday soap across much of West Africa, used for body, face and hair. The original takes its alkali from the ash of plantain skins, cocoa pods or palm leaves, whose main alkali is potassium carbonate, and a soap manual of 1908 already described Fante soap made from palm oil and plantain-skin ash. Makers value it for a quick, rich lather in any water. Here that comes from 70 % palm kernel and coconut oil, cleansing 47 on our scale, with shea for a softer feel. Most of the users surveyed at New York dermatology clinics in 2017 were pleased with black soap, but the authors found very little research on it. The strength is also the caveat: it can feel drying, so it suits oily skin and grubby hands better than dry skin, and many people follow it with a moisturiser.

Sources

What tradition, makers' experience and research say about soaps like this, each labelled for what it is. It is not medical advice, and no soap treats a skin condition: if you have one, ask a doctor or pharmacist.

What the numbers say

  • Lauric acid 34.8 %
  • Myristic acid 11.9 %
  • Palmitic acid 7.0 %
  • Stearic acid 14.2 %
  • Oleic acid 23.1 %
  • Linoleic acid 3.3 %
  • Other 7.9 %

Saturated : unsaturated 74 : 26

Hardness 68 above 29–54
Cleansing 47 above 12–22
Conditioning 26 below 44–69
Bubbly lather 47 above 14–46
Creamy lather 21 16–48

Computed from the fatty acids of the fats above. The bands are what the craft has settled on, not chemistry — a bar outside one is not wrong.

Try it differently

3 variations

The same soap with one thing moved. Each opens in the calculator ready to change again.

From the guides

All guides
Advanced 10 min read

Sodium hydroxide, potassium hydroxide and dual lye explained

Why NaOH makes bars and KOH makes soft soap, converting between them, KOH purity, dual-lye recipes, and the calculator slip that turns a bar caustic.
Intermediate 13 min read

Hot process soap, step by step

Cook soap batter in a slow cooker until the lye is spent, then stir in the superfat oil, fragrance and colour. A full recipe with the calculator's numbers.
Intermediate 11 min read

Superfat and lye discount: why recipes leave some oil unsaponified

What superfat and lye discount mean, how the calculator applies them, where makers set them for each soap, and why oil added at trace isn't the oil left over.

Guides with this recipe

Where these proportions come from

West African black soap is made with potash leached from the ash of plantain skins, cocoa pods or palm leaves, cooked with palm kernel oil and shea butter, often with coconut or palm oil, and judged by eye. This homage keeps fats of that kind, 45 % palm kernel oil, 25 % coconut oil and 30 % shea butter, and replaces the ash with weighed potassium hydroxide at a 6 % superfat, cooked as a soft soap. It does not reproduce the ash's dark colour or the original's rough, crumbly texture.

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