BHT (butylated hydroxytoluene)
Sold to hold off rancidity and orange spots.
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
BHT, butylated hydroxytoluene, is a solid that melts at 70 °C and is listed among pharmaceutical excipients. It dissolves in oils and hardly at all in water, which is why it goes in with the oils.
PubChem primary source, Handbook of Pharmaceutical Excipients primary source
How much
- 0.1 % of the oils in a controlled test filled in Dunn, “The Dreaded Orange Spot” primary source
- up to 0.8 % of the batch by law Regulation (EU) 2022/2195 primary source
The calculator fills in 0.1 % of the oils: 1 g for the 1000 g of oils in its starter recipe.
When and how
- Usually: into the oils.
- Stir it in as it is.
PubChem primary source
What it does to the recipe
- It changes neither the lye nor the water: it is only weight in the bar.
Dunn, “The Dreaded Orange Spot” primary source, PubChem primary source
Worth knowing
- In Dunn’s test, at 0.1 % of the oils, it held off rancidity for 150 hours, and with sodium citrate did best of all. Dunn, “The Dreaded Orange Spot” primary source
- Caution: In the EU, BHT is limited to 0.8 % in rinse-off products such as soap, over concerns about hormone disruption. Regulation (EU) 2022/2195 primary source
Spoons and drops
- 1 tsp ≈ 2.66 g (2.37–2.96 g)
- 1 tbsp ≈ 7.98 g (7.1–8.87 g)
- 1 cup ≈ 128 g (114–142 g)
Handbook of Pharmaceutical Excipients primary source
INCI name
BHT
- CAS number
- 128-37-0
- EC number
- 204-881-4
Guides that discuss it
Sources
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".
PubChem (HSDB), butylated hydroxytoluene: melts at 70 °C; soluble in oils, practically insoluble in water.
Regulation (EU) 2022/2195, Annex III entry 325 to Regulation (EC) No 1223/2009: BHT at most 0.8 % in other leave-on and rinse-off products; restricted over endocrine concerns (recital 2).
Handbook of Pharmaceutical Excipients, 6th ed. (2009), butylated hydroxytoluene: "Density (bulk) 0.48-0.60 g/cm3".