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.