Soap Making with Mimosa Hostilis Root Bark Powder: A Beginner’s Guide
Mimosa hostilis root bark powder, sold in soap making as tepezcohuite, is a natural colourant that gives handmade soap pink-brown to deep brown tones. Use 1 to 2 teaspoons per pound of oils in cold-process soap, mixed into a little oil and stirred in at light trace. This guide covers the amounts, three ways to add it and the problems beginners run into.
How much powder to use
Soap makers measure colourants “per pound of oils” (PPO), meaning the weight of the fats in the recipe, not the finished soap.
| Shade | Powder per pound (454 g) of oils | For a 1 kg batch of oils |
|---|---|---|
| Light | About 1 teaspoon (roughly 5 g) | About 10 g |
| Medium | About 1.5 teaspoons | About 15 g |
| Deep | About 2 teaspoons (roughly 10 g) | About 20 g |
Start at the light end. You can always add more in the next batch, but you cannot take colour out. Very heavy use can make a bar feel scratchy and may tint the lather.
Three ways to add the colour
1. Disperse the powder in oil (the standard method)
Measure the powder into a small cup and stir in about three times its volume of a light oil, such as sweet almond or olive, until there are no dry lumps. Add this mix to the soap batter at light trace, a little at a time, until you like the shade. Dispersing first is what prevents clumps and streaks.
2. Infuse the oils (for a smooth bar with no speckles)
Put shredded bark in a dry jar and cover it with one of your recipe oils, at about 1 part bark to 5 parts oil. Leave it somewhere warm for four to six weeks, or stand the jar in a pan of barely simmering water for a few hours, then strain. Use the coloured oil as part of the oils in your recipe.
3. Colour only part of the batter (for swirls)
Split the batter at light trace, stir the dispersed powder into one portion and leave the other plain. Pour the two together in layers or drag a skewer through them for a marbled bar.
Cold-process method, step by step
- Choose a tested recipe and run it through a lye calculator to confirm the lye and water amounts for your exact oils.
- Put on goggles and gloves. Weigh everything, including the powder.
- Disperse the powder in oil as described above and set it aside.
- Make the lye solution by adding the lye to the water, never the other way round, in a well-ventilated space. Let it cool.
- Melt and combine the oils, then blend in the lye solution until the batter reaches light trace, the point where it leaves a faint trail on the surface.
- Stir in the colour mix. Blend briefly so the batter does not thicken too fast.
- Pour into the mould, cover and leave until firm enough to cut.
- Cut into bars and cure on a rack as your recipe directs, usually four to six weeks.
Using it in melt-and-pour soap
Melt-and-pour base needs less colour. Use up to 1 teaspoon of powder per pound of base, mixed into a tablespoon of 99% isopropyl alcohol so it blends smoothly, and stir it into the melted base a little at a time. Going above that rate can make the colour bleed onto a washcloth.
What colour to expect
In the bar, the powder gives shades from pink-brown to deep brown, often with a fine speckle. Cold-process soap is strongly alkaline while it is fresh, and plant colourants often shift in it, so the colour you see at trace is not the final one. Expect the shade to settle and deepen as the bar cures. A white melt-and-pour base gives softer, pastel versions of the same tones than a clear base.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Clumps or dark specks | Powder added dry | Disperse it in oil first and stir until smooth |
| Scratchy bar | Too much powder | Stay at 1 to 2 teaspoons per pound, or use the infused-oil method |
| Colour on the lather or washcloth | Colourant rate too high | Reduce the amount in the next batch |
| Colour different from last time | Natural variation between batches of bark | Make a small test bar from each new pack |
Safety and labelling
- Lye is caustic. Wear goggles and gloves, keep children and pets away, and work with good ventilation.
- Wear a dust mask when weighing fine powder, and wipe up spills straight away because the powder stains.
- Keep soap-making tools separate from kitchen tools.
- If you sell your soap, check the cosmetic labelling and safety rules that apply where you live.
We sell the bark as a raw material for soap making, dyeing and cosmetic formulation. It is not sold for human consumption.
Common questions
Is tepezcohuite the same as Mimosa hostilis root bark powder?
Yes. Tepezcohuite is the Mexican name for the bark of Mimosa tenuiflora, the tree formerly known as Mimosa hostilis. Soap suppliers use both names for the same powder.
When do I add the powder?
At light trace in cold-process soap, already mixed into a little oil. In melt-and-pour soap, add it to the melted base just before pouring.
Can I add the powder to the lye water instead?
Some makers steep botanicals in the lye solution, but dispersing in oil and adding at trace gives you far more control over the final shade.
How much powder do I need to order?
Very little. A 1 kg batch of oils uses 10 to 20 g, so a 500 g pack colours many batches. The project planner works out the amount for your batch size and gives you a printable sheet.
More short answers are on our FAQ page.
Sources
- Bramble Berry, testing natural colorants: dispersing powders in oil and usage rates.
- Lovin Soap, soapmaking additive chart: per-pound-of-oils rates for botanicals.
- Soap Queen, colouring soap: melt-and-pour rates and colour bleed.
- The Nerdy Farm Wife, herb-infused oils: the 1 to 5 infusion ratio.
