Circle Z soaps
- Sep 10, 2018
- Reaction score
- Tipton IN
Thanks for the hard work. You can also find usage safety from the FDA for metabisulfate and thiosulfate because they are both used in the food and medical industry. I know that metabisulfate is approved for internal consumption but in no way am I recommending that. It is used as a preservative for wine.I did a little web hopping this morning with the goal of learning more about the use of sodium thiosulphate and sodium metabisulfite in cosmetics, especially in terms of safe usage rates. Apologies in advance if information here duplicates anything posted above.
First off, an Aussie soap making supplier has posted results after 5 months for MP soap made with homemade vanilla stabilizer (thiosulphate), here:
Using a readily available and relatively cheap chemical called sodium thiosulphate.www.baysidesoap.com.au
I found a brief discussion of use of thiosulphate and sodium metabisulfite for lotion at this link: sodium thiosulphate....looking to reduce browning (oxidation) with Vanillin — Cosmetic Science Talk
where a poster, Ozgirl, contributed this on why sodium thiosulfate can be listed as fragrance:
“The loophole is probably to do with the IFRA Transparency List.
IFRA Transparency List
IFRA describes two types of ingredients used in fragrances - Fragrance ingredients and Functional ingredients.
Functional ingredients are substances that are not used to provide odor or malodor coverage, but which are essential for the functionality or durability of a fragrance compound – such as an antioxidant, preservative, diluent, solvent or color.
Sodium thiosulfate is listed as being used in fragrances as a functional ingredient so if it is added to your fragrance to stop oxidation you can probably get away with listing the combination (fragrance + sodium thiosulfate) as "fragrance".”
That led me to the IFRA website where I found an August 2019 document from the Cosmetic Ingredient Review Expert Panel (CIR) titled “Safety Assessment of Sulfites as Used in Cosmetics.” I skipped to the end of the long document and on page 52, the conclusion stated is:“The CIR concluded that Sodium Sulfite, Potassium Sulfite, Ammonium Sulfite, Sodium Bisulfite, Ammonium Bisulfite, Sodium Metabisulfite, and Potassium Metabisulfite are safe as used in cosmetic formulations.”
I haven’t been able to find a similar document that specifically discusses sodium thiosulfate/thiosulphate, but found this 2014 CIR document:
which on page 92, states “... the CIR expert panel concludes Sodium Sulphate to be safe as used in rinse-off formulations, and safe up to 1% in leave-on formulation.”
EWG’s Skin Deep rates thousands of personal care product ingredients, culled from ingredient labels on products, based on hazard information pulled from the scientific literature and industry, academic and regulatory databases.www.ewg.org
As for getting to a standardized formula, the pentahydrate version of thiosulfate, which I’ve read is more shelf stable, has 5 attached water molecules compared with the anhydrous form. I think that means more of it is required to get equivalent concentrations of thiosulfate in a solution compared with using the anhydrous form.