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Liquid soaps

Liquid shampoo

A glass squeeze bottle of faintly hazy pale amber liquid shampoo beside a jar of translucent soap paste and a small dish of golden avocado oil on a sage green backdrop

A true-soap liquid shampoo: coconut and olive oil with a fifth castor oil for a lather that holds up in wet hair, a little avocado oil, and jojoba stirred in after the cook. Cooked as a potassium hydroxide paste, diluted to 20 % and scented with rosemary and cedarwood. Best in soft water.

Skill
Advanced
Method
Hot process
Batch
500 g of oils about 1121 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 lidded jar for the paste, then washed squeeze bottles once diluted. Weigh everything, liquids included.

Coconut Oil · 30.0 % 150 g 5.29 oz
Olive Oil · 35.0 % 175 g 6.17 oz
Castor Oil · 20.0 % 100 g 3.53 oz
Jojoba Oil · 5.0 %, stirred in after the cook 25 g 0.88 oz
Avocado Oil · 10.0 % 50 g 1.76 oz
Potassium hydroxide (KOH) · the lye, 90 % pure; if your label says otherwise, weigh 112.3 g at 85 % or 100.5 g at 95 % 106.1 g 3.74 oz
Distilled water · for a 18 % lye solution 500.0 g 17.64 oz
Distilled water for the dilution · about this much, boiling hot: the finished shampoo should weigh 2977 g, so add 2977 g minus your cooked paste's weight, more if the cook drove off steam 1871 g 66.00 oz
Rosemary essential oil · 2.0 % of the oils, after the cook 10 g 0.35 oz
Atlas cedarwood essential oil · 1.0 % of the oils, after the cook 5 g 0.18 oz
Superfat
3.5 %
Temperatures
Lye solution cooled below 82 °C (180 °F), oils 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 paste is cooked. Weigh 150 g of coconut oil, 175 g of olive oil, 100 g of castor oil and 50 g of avocado oil into a slow cooker of 4.5 litres or more and 25 g of jojoba oil into a small jug for later, then 500 g of distilled water into a heat-proof jug and 106.1 g of potassium hydroxide flakes into a dry container; close the flake tub at once.

  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 loudly and gets very hot; let it cool below 82 °C (180 °F), and keep it away from aluminium, tin and zinc, which it attacks, giving off hydrogen.

  3. Warm the oils

    Melt the coconut oil in the slow cooker on low, stir in the olive, castor and avocado oils and bring them to 65 to 71 °C (150 to 160 °F). Leave the jojoba out.

  4. Blend to a paste

    Pour the lye solution into the oils and stick blend in bursts of a minute or two, stirring between them. The batter thickens, separates and thins, then comes back like thick apple sauce, often several times; with water equal to the oils it can take 30 to 60 minutes to hold together as a thick, opaque paste that no longer separates when you stop.

  5. Cover and cook

    Put the lid on and leave the cooker on low. Check after 15 to 20 minutes and again 15 to 20 minutes later, stirring back any liquid that has separated, then stir every 30 to 45 minutes.

  6. Cook until translucent

    Over 3 to 4 hours the paste turns golden and translucent from the edges inwards, softer than a low-water paste. It is ready to test when no opaque, creamy patches come up as you fold it over.

  7. Test a spoonful in boiling water

    Before the jojoba goes in, stir 28 g (1 oz) of paste into 59 ml (2 fl oz) of boiling water until it dissolves, and let it cool. Clear or faintly hazy means the paste is done; milky, or with an oily film on top, means another hour of cooking and a second test.

  8. Stir in the jojoba and weigh

    Turn off the cooker and stir the 25 g of jojoba through the hot paste until it disappears; it goes in now, with no lye counted for it, because it barely saponifies. Let the paste cool and weigh all of it: it will weigh less than the 1106.1 g that went in, because steam left the pot, and the dilution needs the real figure.

  9. Work out the water

    The paste holds 570.5 g of soap, the 475 g of cooked oils plus the 95.5 g of pure potassium hydroxide in 106.1 g of 90 % flakes, and with the jojoba that makes 595.5 g of soap and wax. At 20 % that makes 2977 g of shampoo however much steam the cook drove off, so the water to add is 2977 g minus your paste's weight, about 1.69 g for every gram of paste if it lost none; the liquid soap dilution calculator does the same sum if you give it all 500 g of oils, jojoba included.

  10. Dilute it overnight

    Break the paste into a large pot and pour on all but the last 200 g of that water, boiling hot. Stir gently without whipping up foam, cover it and leave it overnight; the next day, at room temperature, add the rest only if it is still thicker than you want.

  11. Scent it

    Stir half a teaspoon of the rosemary and cedarwood, mixed, into 85 g of the warm shampoo and wait half an hour. If the sample keeps its thickness and does not cloud further, stir the 10 g of rosemary and 5 g of cedarwood oil gently into the whole batch.

  12. Settle and bottle

    Leave it covered for a week or two so any sediment sinks, then pour the shampoo off it into washed and dried squeeze bottles. A faint haze from the jojoba stays, and a thin film may gather on top as it stands, so turn the bottle over gently before use.

  13. Keep it clean

    Diluted, this is four-fifths water and it will be used with wet hands in a warm bathroom, so it can grow bacteria and mould: never top up a bottle, and keep the rest as paste in a closed jar, diluting a little at a time. To keep diluted shampoo for long, or to sell it, it needs a preservative that works at pH 9 to 10, and a challenge test.

  14. Rinse with acid after washing

    Wash, rinse well, then pour a rinse of 1 tbsp of cider vinegar or lemon juice in 250 ml of cool water through the hair and rinse again lightly. Keep the shampoo and the rinse out of your eyes; soap stings.

Tips

  • 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: with 95 % flakes the same weight takes the superfat on the cooked oils from 3.5 % to about −1.9 %, a lye-heavy paste, and the jojoba stirred in afterwards cannot take up that lye.
  • Jojoba is a liquid wax, not an oil, and it barely saponifies in a soap pot. Lye counted for it would only go to the other oils and quietly cut their superfat, so it is left out of the lye and stirred in after the cook. It stays in the shampoo as wax, which with the 3.5 % superfat makes about 5.7 % free oil and wax, more than a clear liquid soap carries, so this one is faintly hazy by design.
  • Soap shampoo works best in soft water. In hard water it leaves a film of lime soap that makes hair dull and tacky, and the acid rinse is how people dealt with that before detergent shampoos. If your water is hard, try it on a small batch first.
  • For a clearer soap to wash with rather than a shampoo, see the liquid body wash, and for a bar, our shampoo bar recipes. Use distilled water for the paste and the dilution, because minerals in tap water add their own haze.

Why make it

This is shampoo the old way. Before detergent shampoos, hair was washed with soap, and liquid potash soaps like this one took over from bars because they wetted hair faster and gave a richer lather (Powers and Fox). Castor oil at a fifth of the oils holds the lather up in wet hair, and cleansing is a moderate 20 on our scale. The drawbacks are well documented. Soap is alkaline, and alkaline shampoos raise the negative charge on hair, so strands rub, tangle and frizz more (Gavazzoni Dias and colleagues). In hard water, soap also leaves a film of lime soap that makes hair tacky and hard to comb, which is why soap shampoos were followed by a lemon or vinegar rinse, and why detergent shampoos, which leave no such film, replaced them. Makers who like it value its short ingredient list, and it suits soft water best.

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 14.7 %
  • Myristic acid 5.7 %
  • Palmitic acid 9.4 %
  • Stearic acid 2.7 %
  • Ricinoleic acid 17.7 %
  • Oleic acid 34.0 %
  • Linoleic acid 7.1 %
  • Other 10.3 %

Saturated : unsaturated 36 : 64

Hardness 33 29–54
Cleansing 20 12–22
Conditioning 60 44–69
Bubbly lather 38 14–46
Creamy lather 30 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 19 min read

Liquid soap from potassium hydroxide paste

Real liquid soap from scratch: a potassium hydroxide paste cooked until it dissolves clear, diluted by weight, thickened with salt and kept free of microbes.
Intermediate 9 min read

Shampoo bars: what true soap does to hair

Soap shampoo bars, honestly: what alkaline soap and hard water do to hair, why an acid rinse helps, when a syndet bar is the better choice, and a recipe.
Advanced 10 min read

Soap in hard water: scum, chelators and rinse

Why soap turns to scum in hard water, how much soap each litre wastes, what a chelator in the bar can and cannot do, and why coconut soap copes best.

Where these proportions come from

Our own formulation: the body wash's potassium hydroxide system with more castor oil, a fifth of the oils, for a lather that holds up in wet hair, avocado oil among the liquid oils and a little jojoba. Jojoba is a liquid wax that barely saponifies in a soap pot, so it is stirred in after the cook and left out of the lye: counted in, its lye would go to the other oils and cut their superfat. The superfat on the cooked oils is 3.5 %, the lowest in half-point steps at which the published saponification ranges cannot leave the paste lye-heavy, and the paste takes water equal to the oils. The method, a paste cooked in a slow cooker until translucent, tested in boiling water and diluted by weight, follows the liquid soap chapter of David Fisher's Complete Photo Guide to Soap Making, as our liquid soap guide does.

Formulation adapted from The Complete Photo Guide to Soap Making by David Fisher (Creative Publishing International, 2018). The method and notes are ours.

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