Lactic Acid Facial Wash Formulation and pH Adjustment

Hello,

Thank you for your detailed questions and sharing your formulation attempts. Based on the information provided by our staff and cosmeceutical7, here are the answers to your questions:

1. Effectiveness of 0.32% Lactic Acid: At a final pH of 5.5, the Lactic Acid ([Product ID: 170]) at 0.32% concentration will primarily function as a pH adjuster to make the formula gentler on the skin. As explained by cosmeceutical7, the exfoliating benefit of AHAs like Lactic Acid depends on the amount of "free acid" available, which is significantly reduced at higher pH levels. At pH 5.5, the bioavailability for exfoliation is minimal to none.
2. Using Sodium Bicarbonate for pH adjustment: It is acceptable to use Sodium Bicarbonate ([Product ID: 610]) to adjust the pH if it drops too low, especially to ensure the formula is within a skin-compatible range (generally pH 3.5-6.5). Your final pH of 5.5 is within this healthy range. However, as discussed, raising the pH using a base like Sodium Bicarbonate will neutralize the Lactic Acid and reduce or eliminate its exfoliating efficacy.
3. Including Sodium Bicarbonate for higher Lactic Acid concentration: If your goal is to achieve the exfoliating benefit of Lactic Acid ([Product ID: 170]), you should not use Sodium Bicarbonate ([Product ID: 610]) to raise the pH after adding Lactic Acid. The exfoliating action requires the Lactic Acid to be in its free acid form, which is present at lower pH levels (ideally below 4.0, with increasing bioavailability as pH decreases). Adding Sodium Bicarbonate raises the pH and converts the Lactic Acid into its salt form (lactate), losing the exfoliating effect. Your experiments show that even 0.5% Lactic Acid brings the pH down significantly (to 3.6). Using 3% Lactic Acid results in a very low pH (2.8), which would be effective for exfoliation but likely too irritating for a facial wash. For a wash-off product, you need to balance exfoliation effectiveness (lower pH) with potential irritation (higher pH). A pH in the range of 3.5-4.0 might be a reasonable target for some exfoliating benefit in a wash-off, although it won't be as potent as a leave-on treatment. To achieve this pH, you would add Lactic Acid until the desired pH is reached, without adding Sodium Bicarbonate afterwards unless the pH is excessively low (e.g., below 3.5, depending on desired irritation level).
4. Adjusting other "clear substances": The base formula components (Water [Product ID: 838], Disodium EDTA [Product ID: 184], Lauryl Glucoside [Product ID: 177], Coco Betaine [Product ID: 160], Creamy Foamer [Product ID: 305], Glycerin [Product ID: 143], Vitamin B5 [Product ID: 111], Phenoxyethanol [Product ID: 155]) seem to form a gentle cleansing base with good foam, as noted by our staff. Without a specific goal for adjusting these (e.g., wanting more/less foam, different texture, different feel on the skin), the current levels appear suitable for a standard gentle facial cleanser. If you have a particular outcome in mind, please let us know, and we can provide more specific recommendations.

Hope this clarifies your questions!

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