I’ve been working on a DIY beta hydroxy solution that doesn’t contain any alcohol, and I pestered the chemist over at The Personal Formulator about solubility, and they were pretty informative:
Salicylic acid is only slightly soluble in water, one gram dissolves in 460mL water. To incorporate salicylic acid to a formulation, the following methods can be used:
1) it can be added to the oil phase of the emulsion and heated to 80-85C
2) it can be added to a water phase containing sodium phosphate, borax, alkali acetates or citrates to increase its solubility in water
3) it can be combined with a glycol, such as propylene glycol
Since I’m not gung-ho about using borax, glycols or any other unnecessary chemicals, I went ahead and tried to dissolve it in oil alone. However, the crystals seem to re-crystalize once the oil returns to room temperature. I’ve been shaking the solution vigorously and applying it anyway, and I haven’t had any problems — but I’m just not convinced it works well.
Blast it, I wish I knew more about solubility and other basic chemistry concepts! Next time, I’ll be trying to add it to a lecithin-emulsified solution to see if that helps. If any other skincare gurus have ideas, please share them!