Glycerin (99 %)
Transparent soap. In hot process, it helps the cooked soap flow. Lovin Soap supplier or guide, Grosso, The Everything Soapmaking Book, 3rd ed. primary source
Opens the calculator’s starter recipe with this additive in it. No source gives a dose to fill in, so enter your own.
What it is
Glycerin, also called glycerol, is a liquid sold here at 99 %, which weighs 1.2585 g per mL at 20 °C. Transparent soap recipes use a lot of it.
Glycerine Producers’ Association primary source, Lovin Soap supplier or guide
How much
- 25 % of the oils for transparent soap Lovin Soap supplier or guide
- 14.9–20.5 % of the oils for transparent soap (from a published recipe) Simmons & Appleton primary source
- 1 tbsp per pound of oils in hot process Grosso, The Everything Soapmaking Book, 3rd ed. primary source
- up to 8 % of the batch in melt and pour or rebatch Simmons & Appleton primary source
- up to 99.4 % of the batch in rinse-off products, the highest reported use: not a recommendation CIR primary source
No dose to fill in: enter your own.
When and how
- Usually: into the oils.
- Also used: after the cook.
- Stir it in as it is.
Lovin Soap supplier or guide, Grosso, The Everything Soapmaking Book, 3rd ed. primary source
What it does to the recipe
- It changes neither the lye nor the water: it is only weight in the bar.
Glycerine Producers’ Association primary source
Worth knowing
- No source gives a dose for cold-process soap: the doses here are for other kinds of soap.
- Caution: Too much makes a sticky bar that sweats in damp air. Failor, Transparent Soapmaking primary source
Spoons and drops
- 1 tsp ≈ 6.2 g
- 1 tbsp ≈ 18.6 g
- 1 cup ≈ 298 g
- 1 drop ≈ 42.5 mg (42–43 mg): droppers differ
Glycerine Producers’ Association primary source, Österreichisches Arzneibuch primary source
INCI name
Glycerin
- CAS number
- 56-81-5
- EC number
- 200-289-5
Recipes that use it
Guides that discuss it
Sources
Lovin Soap, transparent soap: "Glycerin – 125 grams (25% of oils)", melted with the oils.
Alicia Grosso, The Everything Soapmaking Book, 3rd edition (Adams Media, 2013). Chapter 8, hot process: recipes on a "2-pound batch recipe of your choice" that each "YIELDS 3 POUNDS", the addition stirred "into the neutral soap" after the cook: "3 tablespoons baking soda" and "2 tablespoons lemon zest" (Lemon/Baking Soda Kitchen Soap), "2 tablespoons yellow cornmeal", "1 tablespoon dried lavender flowers", "1 tablespoon mint, dried and ground", "1 tablespoon dried yarrow"; "You can add liquid glycerin to hot-process soap to get it to flow more easily from the mold. Use 1 tablespoon for each pound of oils in the batch." Chapter 9, transparent soap: 19.5 oz of oils with "10 ounces (plus 2 ounces more if needed for clarity) 90 percent ethanol (190 proof vodka)" (190 proof is 95 %) and "5 ounces sugar"; "Alcohol fumes are highly flammable." Chapter 11, Lavender Oat Float: "1 tablespoon dried lavender flowers" for "1 pound casting soap".
Glycerine Producers’ Association, Physical Properties of Glycerine and its Solutions (1963), Table 3: 99 % glycerol, 1.2585 g/mL at 20 °C.
W. H. Simmons and H. A. Appleton, The Handbook of Soap Manufacture (Scott, Greenwood & Son, London, 1908), pp. 57–58, transparent soaps: for 112 lb of fats, "Twenty-three lb. of pure glycerine" and "the alcohol, which would be 45 lb. in this example"; with castor oil, 168 lb of oils and "the glycerine (25 lb.)" or "47 lb. of alcohol"; "the 'sugar solution' is prepared by dissolving 50 lb. cane sugar in 50 lb. water"; "If the sample be firm but opaque, more sugar solution is required". The alcohol’s strength is not given.
W. H. Simmons and H. A. Appleton, The Handbook of Soap Manufacture (Scott, Greenwood & Son, London, 1908), p. 89, glycerine in milled toilet soap: "In some cases, however, a much larger quantity is desired, up to some 6 or 8 per cent. To mill this in requires great care, otherwise the soap tends to blister during compression."
Cosmetic Ingredient Review, glycerin (2014): up to 99.4 % in skin cleansing products.
The highest concentration reported to CIR in industry surveys: what has been used, not a recommendation.
Catherine Failor, Transparent Soapmaking (1997): too much glycerin "can cause a bar of soap to “sweat.”"
Österreichisches Arzneibuch (ÖAB), drop table for the Ph. Eur. standard dropper at 20 °C (2024 draft, BASG): refined olive oil 22 mg a drop, sunflower and castor oil 24 mg, lactic acid 29 mg, glycerol 42–43 mg.