So, I was recently asked by a colleague, why do some lotions whiten when you rub them in and others don't. Now, I have always been taught that it is bad if a skincare lotion whitens as you rub it in, as that is the sign of a cheaper/low end lotion but to be honest I'm not quite sure what the cause of it is. Is it due to a soaping out effect? For example is it due to a higher portion of saponifiable vs unsaponifiable content? Aka too many esters in the presence of NaOH? Could this be prevented by switching to a weaker base such as TEA (triethanolamine)?
Any advice would be appreciated! I tried searching the literature, but I did not have very much luck and at this point I am only speculating.