Sodium citrate
Binds hard-water minerals, for less soap scum.
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
Sodium citrate is a salt of citric acid, sold dry as trisodium citrate dihydrate, which is 11–13 % water. It is fully neutralised, so it takes no lye.
Jungbunzlauer primary source, Jungbunzlauer primary source, Classic Bells supplier or guide, CIR primary source
How much
- 1.3–3.9 % of the oils filled in Classic Bells supplier or guide
- 3 % of the oils in a controlled test Modern Soapmaking supplier or guide
- 0.1 % of the oils in a controlled test Dunn, “The Dreaded Orange Spot” primary source
- up to 10 % of the batch in rinse-off products, the highest reported use: not a recommendation CIR primary source
The calculator fills in 1.3 % of the oils: 13 g for the 1000 g of oils in its starter recipe.
When and how
- Usually: into the oils.
- Also used: in the water, before the lye.
- Dissolve it in about twice its weight of the recipe’s water, then blend that into the oils.
Classic Bells supplier or guide
What it does to the recipe
- It changes neither the lye nor the water: it is only weight in the bar.
Classic Bells supplier or guide, Jungbunzlauer primary source
Worth knowing
- On its own, at 0.1 % of the oils, it did nothing against rancidity in Dunn’s test; with 0.1 % BHT the pair may prevent orange spots. Dunn, “The Dreaded Orange Spot” primary source
- Too much can leave white crystals on the soap. Classic Bells supplier or guide
Spoons and drops
- 1 tsp ≈ 4.56 g (3.7–5.42 g)
- 1 tbsp ≈ 13.7 g (11.1–16.3 g)
- 1 cup ≈ 219 g (177–260 g)
Jungbunzlauer primary source
INCI name
Sodium Citrate
- CAS number
- 68-04-2, 6132-04-3
- EC number
- 200-675-3
Guides that discuss it
Sources
Classic Bells, "Sodium citrate": "13 g to 39 g sodium citrate powder for every 1,000 g fats (1.3% to 3.9%...). Use more for hard water, less for soft"; dissolve it in about twice its weight of water and blend into the oils; "DO NOT add additional lye if you are using citrate"; too much leaves white crystals.
Jungbunzlauer, Personal Care folder (2025): sodium lactate, sodium citrate and sodium gluconate are "Fully neutralised salts"; sodium gluconate is "particularly adapted for mass market soap and bath products" and, in strongly alkaline solutions, "surpasses all other chelating agents, such as EDTA".
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."
Kevin M. Dunn, "The Dreaded Orange Spot", The Handcrafted Soapmaker (Winter 2005/06): additives at 0.1 % of the oil weight in olive-oil soap held at 60 °C. Rosemary extract and EDTA "lengthened the induction period beyond 300 hours", BHT to 150; grapefruit seed extract, vitamin C, vitamin E and sodium citrate were "virtually identical" to plain olive-oil soap; BHT with sodium citrate did best, and "ROE + Sodium Citrate actually performed worse than ROE alone".
Cosmetic Ingredient Review, citric acid and its salts (2012): up to 10 % in rinse-off products.
The highest concentration reported to CIR in industry surveys: what has been used, not a recommendation.
Jungbunzlauer, Trisodium Citrate Dihydrate data packet: bulk density 750–1100 kg/m³; water (loss on drying) 11.0–13.0 %.