[northernlights]

Thank you so much fro the explanation, it is very helpful!

chemicalmatt said:

What you are noting is the free alkali hydroxide species used to form water-soluble thioglycolate salts with 80% thio (aka mercaptoacetic) acid. We made thioglycolates in situ with these, balancing the calcium hydroxide (add first!) with some sodium thio salt and free alkali. Calcium thio is the safer keratoyltic if I remember - and its been a long while - while sodium hydroxide merely boosts the pH to 12.5 necessary to work fast. Similar to activity of alpha/beta hydroxyacids on the low end of the pH scale, alkali thioglycolates work just as well at pH9 but a LOT SLOWER and that gives them more  time to irritate your skin, thus the pH boost. 15 minutes contact time and wipe away the hair.