Bentonite clay
Slip and glide, for shaving soap. More lather, with a creamy touch. Corley Barto, The Natural Soap Chef primary source, Modern Soapmaking supplier or guide
Opens the calculator’s starter recipe, 1000 g of oils, with this additive at the dose it fills in, ready to change.
What it is
Bentonite is a clay that swells as it takes up water, into a malleable mass; sodium bentonite swells more than calcium bentonite. It has a monograph in the European Pharmacopoeia.
Ph. Eur. primary source, From Nature With Love supplier or guide
How much
- 1 tbsp per pound of oils in a controlled test filled in Modern Soapmaking supplier or guide
- 2.12 tsp per pound of oils (from a published recipe) Faiola, Pure Soapmaking primary source
- 0.67–1.33 tbsp per pound of soap (the source gives it for a batch of stated size, worked out here per pound) Cavitch, The Natural Soap Book primary source
- 0.57–1.71 tbsp per pound of soap in melt and pour or rebatch (from a published recipe that adds it to one part of the batch: the lower figure over the whole batch, the higher within that part) Fisher, The Complete Photo Guide to Soap Making primary source
- 0.22–4.7 % of the batch in rinse-off products, the highest reported use: not a recommendation CIR primary source
The calculator fills in 1 tbsp per pound of oils: 25.8 g for the 1000 g of oils in its starter recipe.
When and how
- Usually: at light trace.
- Mix it with about three times its volume of the recipe’s water, held back for it: a teaspoon of powder to a tablespoon of water.
Bramble Berry supplier or guide
What it does to the recipe
- It changes neither the lye nor the water: it is only weight in the bar.
Worth knowing
- It swells with water into a thick mass. Sodium bentonite swells more than calcium bentonite. Ph. Eur. primary source, From Nature With Love supplier or guide
- It speeds trace. Soap Queen supplier or guide
Spoons and drops
- 1 tsp ≈ 3.91 g (3.47–4.34 g)
- 1 tbsp ≈ 11.7 g (10.4–13 g)
- 1 cup ≈ 188 g (167–208 g)
Wyo-Ben; Black Hills Bentonite primary source
INCI name
Bentonite
- CAS number
- 1302-78-9
- EC number
- 215-108-5
Recipes that use it
Guides that discuss it
Sources
Heidi Corley Barto, The Natural Soap Chef (Ulysses Press, 2012), chapter 1: "Clays add color and slip to your soap"; "I use bentonite clay in my shaving bars". Chapter 5, a facial bar: "bentonite clay gives extra “slip” to soap".
Modern Soapmaking, lather additive testing: sodium lactate 0.25 oz per pound of oils; sugar and bentonite 1 tablespoon per pound of oils; sodium citrate 3 %; yogurt for 58 % of the water. Of the bentonite bar: "Many soapmakers add various clays to their soaps to increase slip and glide, to make shaving soaps. It also adds a nice creamy touch with an increase on lather."
Bramble Berry, bentonite clay: "mix 1 teaspoon with 1 tablespoon of distilled water".
Anne-Marie Faiola, Pure Soapmaking (Storey Publishing, 2016), recipes in chapters 8–10. 100% Castile-Brine Stamped Cube: "1 tablespoon sea salt" dissolved in the water before the lye, for 33 oz of olive oil. Oatmeal Soap for Babies: "2 teaspoons bentonite clay dispersed into 4 tablespoons distilled water" and "2 tablespoons colloidal oatmeal" at thin trace, for 15.1 oz of oils whose olive oil is infused with "2 tablespoons Egyptian chamomile" in a teabag in 14.5 oz of oil, 2 hours in a double boiler. Nettle & Yarrow Upcycle: "2 teaspoons dried yarrow powder dispersed into 1 tablespoon apricot kernel oil" in one of two halves of 24.1 oz of oils. Buttermilk Honeycombs: "3 tablespoons honey" at thin trace for 25.1 oz of oils. Banana Cream Pie Layered Bars: "1.2 ounces banana, 1.5 ounces whipping cream, and 1.5 ounces water, pureed" at thin trace for 35.2 oz of oils, then the freezer "for 24 hours to avoid overheating from the sugars in the banana". Annatto-Yarrow with Embeds: "1 tablespoon spirulina powder" and "1 teaspoon yarrow powder", added "directly to the hot lye-water", for 7.1 oz of oils; "2 tablespoons poppy seeds" in one of two halves of 34 oz of oils. Cucumber Layers: "1 ounce cucumber puree" into the whole batch at thin trace, 22 oz of oils. Gardener Scrub with Coffee Grounds: 50 oz of oils, the batter divided "into four exactly equal sections", one each for "5 teaspoons paprika", "5 teaspoons ground orange peel dispersed into 1 tablespoon of canola oil", "5 teaspoons brewed coffee grounds" and "10 teaspoons green zeolite clay". Indigo-Annatto Negative-Space Funnel Pour: "1.5 tablespoons indigo powder" whisked into the lye-water and "1 tablespoon alkanet root powder dispersed into 1 ounce sunflower oil" at very thin trace, 35.2 oz of oils; "In order to bring out the best color for the indigo powder, the soap must go through a hot gel phase". Black Tea Funnel Pour: 5.5 oz of brewed black tea added at thin trace, 5.5 oz of water for the lye, 33.1 oz of oils. Goat Milk Sunset Burst: "0.7 ounce goat milk powder dissolved in 1 ounce distilled water" for 17.1 oz of oils and "1 ounce goat milk powder" for 25.2 oz, added at trace: "To help avoid scorching, this recipe incorporates the goat milk by using a concentrated solution of powdered goat milk."
Susan Miller Cavitch, The Natural Soap Book (Storey Publishing, 1995), chapter 6: clay, "add the clay to your soap just before pouring into molds, using ½ to 1 cup (118 to 237 ml) for a 12-pound (5.45 kg) batch of soap. Before adding the pure essential oils, blend the clay with 2 cups (473 ml) of soap mixture in a small container" (pp. 62–63); "Oatmeal, cornmeal, flax seed meal, juniper berry meal, alfalfa meal, flaked seaweed, and jojoba meal can all be added to soap for texture. Oatmeal, jojoba meal, and alfalfa meal exfoliate gently. Juniper berry, flaked seaweed, and flax seed meals are more coarse, with sharper edges; finely grind them before adding as exfoliants to soap"; "½ to 1 cup (118 to 237 ml) of meal is suggested for a 12-pound (5.45 kg) batch of soap", added "immediately after the soap has saponified" (pp. 66–67). ½–1 cup for 12 pounds is 0.67–1.33 tablespoons per pound of soap.
David Fisher, The Complete Photo Guide to Soap Making (Creative Publishing International, 2018): rebatched soaps, "1 tablespoon (6 g) red sandalwood powder" for 1 lb (454 g) of grated soap, and "1 tablespoon (1.5 g) lightly crushed rose petals buds" for a pound (p. 34); "1 to 2 tablespoons (5 to 10 g) ground walnut shells" in one third of 28 oz (794 g) of grated soap (p. 32); "1 tablespoon (9 g) kaolin, bentonite, or French green clay" in another third and "1 teaspoon activated charcoal—a little goes a long way" in the last (p. 32); "2 tablespoons (10 g) lightly ground oatmeal" for 1 lb (454 g) of grated soap (p. 32); in melt and pour, "¼ teaspoon cosmetic glitter" in about 4 ounces (112 g) of clear base (p. 54); in cold process, "2 teaspoons activated charcoal per 1 lb (454 g) of soap oils" (p. 121), and for the three colours of a clay swirl "½ teaspoon rhassoul clay", "½ teaspoon green sea clay" and "½ teaspoon red Moroccan clay", each mixed with 3 tablespoons (45 ml) of distilled water (pp. 121–122).
Cosmetic Ingredient Review, natural clays (2023): kaolin 1–5 %, bentonite 0.22–4.7 % and illite up to 0.34 % in bath soaps and detergents; montmorillonite up to 3 % in rinse-off products.
The highest concentration reported to CIR in industry surveys: what has been used, not a recommendation.
European Pharmacopoeia 7.0, Bentonite: "It swells with a little water forming a malleable mass."
From Nature With Love, bentonite: "Sodium Bentonite Clay possesses a higher swell".
Wyoming sodium bentonite: Wyo-Ben Big Horn 200, 52 ± 3 lb/ft³, and Big Horn 325, 44–50 lb/ft³; Black Hills Bond, 53 lb/ft³ uncompacted (0.71–0.88 g/mL).
Industrial grades; cosmetic bentonite is sold without a bulk density.