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Nettle and yarrow split bar

Square bars of soap split corner to corner into soft khaki green and pale yellow-tan halves, beside dried nettle leaves and yarrow flowers, on a purple backdrop

A square bar split corner to corner, soft green nettle on one side and pale yellow yarrow on the other, poured into a milk carton with a card divider. The beeswax recipe is soaped hot, then frozen so it stays out of gel.

Skill
Intermediate
Method
Cold process
Batch
600 g of oils about 869 g of batter
Hands-on
1 h 15 min
Cure
6 weeks
Gel phase
No keep it cool
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What you need

For 600 g of oils, which fills a 1 litre gable-top milk carton with its top cut off, and a card divider. Weigh everything, liquids included.

Olive-Pomace Oil · 39.0 % 234 g 8.25 oz
Rice Bran Oil · 25.0 % 150 g 5.29 oz
Coconut Oil · 24.0 % 144 g 5.08 oz
Apricot Kernel Oil · 5.0 % 30 g 1.06 oz
Castor Oil · 3.0 % 18 g 0.63 oz
Shea Olein · 2.0 % 12 g 0.42 oz
Beeswax · 2.0 % 12 g 0.42 oz
Sodium hydroxide (NaOH) · the lye, 100 % pure 82.3 g 2.90 oz
Distilled water · for a 33 % lye solution 167.0 g 5.89 oz
Nettle leaf powder · green half only, about 1½ tsp dispersed in 10 g of the recipe's apricot kernel oil 2.5 g 0.09 oz
Yarrow powder · yellow half only, about 1½ tsp dispersed in 10 g of the recipe's apricot kernel oil 2.5 g 0.09 oz
Litsea oil · 1.5 % of the oils, at trace 9 g 0.32 oz
Clary sage oil · 0.5 % of the oils, at trace 3 g 0.11 oz
Roman chamomile oil · 0.5 % of the oils, at trace 3 g 0.11 oz
Superfat
5 %
Temperatures
Beeswax melted with the coconut oil at about 65 °C (149 °F); oils and lye solution at 52 to 60 °C (125 to 140 °F) when they meet

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Method

  1. Prepare the carton

    Rinse and dry a 1 litre gable-top carton from fresh milk or juice, waxed or plastic-coated inside, never a long-life carton lined with foil, and cut the top off where the gable starts. Cut a strip of stiff card to fit corner to corner inside it, about 10 cm across a 7 cm carton and as tall as the carton, and wrap it in packing tape so it can't soak up water.

  2. Get ready

    Put on goggles, gloves and long sleeves, open a window, and clear an upright space in the freezer. Stand the carton in a small box or between two heavy tins so it can't tip, with two spouted jugs beside it.

  3. Disperse the colours

    Weigh the 30 g of apricot kernel oil and put 10 g in each jug. Stir the nettle powder into one and the yarrow powder into the other until smooth.

  4. Make the lye solution

    About half an hour before you soap, pour the 82.3 g of sodium hydroxide slowly into the 167.0 g of water where the air moves, never the reverse, and stir until clear. This batch is soaped hot, so the solution only needs to cool to 52 to 60 °C (125 to 140 °F).

  5. Melt the wax into the oils

    Melt the beeswax and coconut oil together on low heat until the wax has fully melted, at about 65 °C (149 °F). Warm the olive pomace, rice bran, castor and shea oils with the last 10 g of apricot kernel oil to about 55 °C (131 °F) and pour the wax mixture in slowly, stirring; if it clouds, warm it gently until clear.

  6. Blend briefly

    When the oils and the lye solution are both at 52 to 60 °C (125 to 140 °F), pour the lye in down the blender shaft and blend in short pulses for about 10 seconds, just to very light trace: heat and wax make this batter move fast. Stir in the essential oils by hand.

  7. Colour the halves

    Pour 422 g of batter into each jug, the second taking what is left, and whisk until each colour is even.

  8. Pour both sides

    Stand the divider in the carton from corner to corner. Pour the green into one side and the yellow into the other at the same time, or a little of each in turn, keeping the two levels within about 1 cm of each other so the divider doesn't lean.

  9. Lift the divider

    Pull the divider straight up and out in one slow movement, then tap the carton gently on the worktop to bring up air.

  10. Freeze it

    Stand the carton upright in the freezer for 4 to 6 hours. In a tall, narrow mould only the middle would gel, leaving a darker core in every bar, and the freezer keeps it all out of gel.

  11. Let it set

    Take the carton out and leave it at room temperature for 2 to 3 days, until the soap is firm.

  12. Peel the carton

    Snip the top edge and tear the carton away in a spiral, with gloves on. If it clings, freeze it for 2 hours and try again.

  13. Cut

    Cut the column into slices about 2.5 cm (1 in) thick: about seven square bars, each split corner to corner into green and yellow.

  14. Cure in the dark

    Stand the bars on edge with air between them for 6 weeks, turning them every few days, somewhere dark.

Tips

  • Expect soft colours that keep moving. Nettle starts a gentle green and drifts towards khaki over the weeks, faster in light, though Faiola finds it steadier than most natural greens; yarrow gives a pale yellow-tan. Faiola gets a yellower yarrow by stirring it into the hot lye solution, but here that would tint the green side too.
  • The calculator charges beeswax lye for its whole saponification value, about half an ordinary oil's, though most of the wax passes into the bar unchanged, so the true superfat sits a little above 5 %. At 2 % of the oils that is harmless. To soap cooler, replace the beeswax with more olive pomace oil and run the recipe through the calculator again.
  • Olive pomace oil brings on trace sooner than extra virgin olive oil, which suits a quick pour like this one. With extra virgin, expect to blend a little longer.

Why make it

A small, pretty batch: nettle green and yarrow yellow meeting corner to corner in every bar, poured in a milk carton so it needs no special mould. Both plants belong to European country tradition, and yarrow's botanical name, Achillea, comes from the legend of Achilles; in this soap they are colourants only, a couple of grams each, and do nothing more for skin. The formula is gentle, cleansing 17 and conditioning 62 on our scale, with rice bran oil and a little beeswax, so it suits everyday washing. One caveat matters. Yarrow and chamomile both belong to the daisy family, and DermNet advises people with a daisy-family (Compositae) allergy not to use cosmetics made with these plants. If that is you, skip this bar, or make it without the yarrow and the Roman chamomile oil.

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 11.8 %
  • Myristic acid 4.7 %
  • Palmitic acid 12.6 %
  • Stearic acid 3.2 %
  • Ricinoleic acid 2.7 %
  • Oleic acid 43.8 %
  • Linoleic acid 14.8 %
  • Other 5.2 %

Saturated : unsaturated 37 : 63

Hardness 32 29–54
Cleansing 17 12–22
Conditioning 62 44–69
Bubbly lather 19 14–46
Creamy lather 18 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.

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Where these proportions come from

Adapted from Anne-Marie Faiola's nettle and yarrow bar: her palm-free oils with 2 % beeswax, soaped hot and then frozen, her milk-carton mould and diagonal divider, and her nettle and yarrow dispersed in apricot kernel oil. We use a 33 % lye solution in place of her 29 %, leave out her titanium dioxide, and cut her clary sage, chamomile and litsea from 4.1 % of the oils to 2.5 %.

Formulation adapted from Pure Soapmaking by Anne-Marie Faiola (Storey Publishing, 2016). The method and notes are ours.

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