30% Salicylic Acid Peel - Crystals??

mflick1mflick1 Member
edited February 2014 in Formulating
Hello All, 

Hope someone can offer some help on this. I made a 30% Salicylic Acid Peel solution (I made about six bottles, 120 ml ea) and the next day there were crystals at the bottom that formed. What could have caused these crystals. 

I added the Salicylic Acid, powder form, in SDA 40, added a little heat until acid dissolved and then added NaOH to adjust pH. 

Any advise?

Also, if I made this un-buffered and did not use NaOH to adjust pH, maybe I could avoid this next time? 

Thank you!


  • Is 30% salicyclic acid permitted in cosmetics products that arent intended to be diluted?
  • chemicalmattchemicalmatt Member, Professional Chemist

    Can anyone say "supersaturation"? Your product, settled, cooled crystallized. This is Physical Chemistry 101. You'll need a co-solvent, dude.  I advise ethoxtdiglycol or propylene glycol.  Check the Merck Index for solubitlity parameters.

  • Hummm.... Well I first wanted to make this un-buffered but guess I did my initial math incorrect since my pH wasn't as close as I wanted it to be. So how do you explain other manufactures out their who make un-buffered solutions which is just the Salicylic Acid and ethanol? You don't HAVE to have buffers.

    I'll guess I keep playing with it..... Also, I did think of supersaturation, again, guess my math was off, I'll have to go back and review

    O and yes chemical peels are permitted...
  • Bill_TogeBill_Toge Member, Professional Chemist
    @mikebavington not in Europe, the limit is 3% in rinse-off hair products and 2% in everything else
    UK based cosmetic chemist with 13 years' experience at the bench. I've worked with pretty much everything apart from pressed powders, soap, solid lipstick and aerosols.
  • I know peels are permitted, but I think 30% might be against your country's regulations. Where do you live?
  • I'm in the US, we are a physicians only line. I've been in regulatory and compliance for many years so I'm not concerned with that. I'm switching to R&D and I've been working under our chemist while trying to earn my second degree in science but she is out on vacation for two weeks, hence the help on this issue.
  • DavidWDavidW Member, PCF student
    What Chemicalmatt said.  You need other solubilizers.  As a manufacturer I have customers asking me for all sorts of crazy peels lately including high Sal. Acid
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