AHA in Glycerin Soap: Effectiveness and pH Issues
Question
Can Alpha Hydroxy Acid (AHA) be effectively used for exfoliation in a glycerin bar soap formulation? What are the pH considerations and potential formulation challenges?
Answer
Hello, thank you for sharing your glycerin soap recipes and asking about the use of AHA.
Your concern about the AHA's effectiveness in this formula is valid. Alpha Hydroxy Acids (AHAs) like the one you are using require a low pH environment, typically between 3.0 and 3.5, to effectively exfoliate the skin.
However, traditional bar soaps, including glycerin soaps, are naturally alkaline and have a high pH (usually well above 7). In this high-pH environment, the AHA will be largely neutralized and will not provide the exfoliating benefits you might expect.
Furthermore, attempting to lower the pH of a standard soap base to the effective range for AHA would likely prevent the soap from solidifying properly, resulting in a liquid or unstable product.
While ingredients like glycerin and coco betaine are commonly used in soap formulations, incorporating AHA for its exfoliating action is chemically challenging in a standard high-pH bar soap format.
As mentioned by others, achieving a stable, low-pH bar soap is possible but requires specialized formulations and ingredients beyond a simple melt-and-pour or standard soap base.