D I Why?
June 28, 2008 9:34 pm Body Care, Facial SkincareI’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!
Nimue :
Date: July 12, 2008 @ 4:45 pm
Try throwing it into a blender! I was able to make a smooth cleanser (with solid cetearul alcohol flakes) by blending it. It stayed mostly smooth.
Psychic Advice :
Date: July 13, 2008 @ 5:22 am
Great blog, subscribed to your rss feed. Thanks.
Virginia :
Date: July 13, 2008 @ 10:07 am
@Nimue — you know, I used a hand mixer when I originally created it, and I’ve mixed it significantly since. But it’s not an issue of just blending — the salicylic acid is only *slightly* oil-soluble, and I think it has a tendency to re-crystalize at lower temperatures.
I suppose I could keep re-heating the mixture every few days, but that’s a pain in the ass and I don’t want to cook out all the benefits of my cold-pressed, unrefined oils!
I’m sure there’s some creepy chemical I could add that would hinder the re-crystalization process. I just have to figure out what that is, and whether it’s worth it to include! Sigh. Wishing I’d taken chemistry back in high school or college — how did I manage to squeak around that?