Switching betaine to sultaine (stability issue)

I have a facial cleansing formula that passed stability testing with surfactant system consisting of 70% cocamidopropyl betaine and 30% coco glucoside (by solids). I tried swapping sultaine for betaine, with no other changes to the formula, and adjusted to same pH (5.0). The sultaine-replaced product had obvious separation at 40C and RT by day 2. Can anyone think of a reason this might have occurred?

I admit I have not duplicated the failed result, and intend to attempt it tomorrow, but thought I'd check if anyone has insight. Thanks in advance.

Comments

  • Update: I duplicated the failure, and appears to me that xanthan gum is settling to the bottom. I again made the stable cleanser formula with exactly the same process and % solids, except that I replaced cocamidopropyl betaine with cocamidopropyl hydroxysultaine. I adjusted pH to 5.4 and let the solution sit overnight at RT before the final step of adjusting viscosity with xanthan gum (pre-wetted with glycerin). Looked like a gorgeous solution the next morning, until I added the xanthan gum. Despite what I consider adequate mixing, I have an opaque layer at the bottom of the vessel that appeared within an hour or two -- it's about 15% the total height of the mixture. Wondering if anyone has any thoughts how to correct this, or an alternative thickener for sultaine + coco glucoside that would have an EWG hazard score no higher than 2?
  • EWG? EWG??????@!@!!! Words fail me.
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  • It is difficult to give you any advice without knowing all the ingredients in the formula.
  • Belassi said:
    EWG? EWG??????@!@!!! Words fail me.

    It's a trend these days to have formulas that only use ingredients approved by larger sites like EWG. There are products out there that claim to use only green-labeled (for safe) ingredients, like the Purito Centella Green Level Buffet Serum, which is very funny because the enormous amounts of lavender oil in it irritated my skin. Just shows that it's the dose that makes the poison!

    I think this trend will go away quickly, for what it's worth.
  • Xanthan gum is anionic, CAPB changes it’s charge to cationic at pH lower than 6. You have a conflict of charges here so xanthan separates. I haven’t worked with sultaine but assuming all amphoterics are similar elevate pH to 7 and see whether it passes stability.
  • And speaking about thickeners, that formula is going to be tricky (glucosides....) - crothix liquid is the king
  • Many thanks to ngarayeva001 for the professional and helpful posts. I was considering Crothix...
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