Instability in Hair Styling Product Emulsion After Adding Lactic Acid

Hello,

Regarding the issue of your hair styling product emulsion becoming unstable after adding Lactic Acid, it's likely due to an incompatibility between the Lactic Acid and your emulsifier system (PEG-40 and Glyceryl Stearate SE). Acids can sometimes disrupt the stability of certain emulsions.

As the staff previously advised, a pH of 7.1 is perfectly acceptable for hair styling products as it is close to the natural pH of hair and skin (around 5.5). There is no strict requirement to lower the pH further if 7.1 is already suitable and stable.

Considering your options:

1. Cutting Lactic Acid from the formula: This is the most straightforward solution. Since pH 7.1 is acceptable and stable, removing the ingredient that caused instability will likely restore the desired texture. This aligns with the staff's recommendation.
2. Changing emulsifiers: This is a possibility if you absolutely need to incorporate Lactic Acid or achieve a lower pH. Some emulsifiers are more acid-stable than others. However, this requires significant reformulation and testing.
3. Increasing emulsifiers: While sometimes helpful, simply increasing the amount of the current emulsifiers might not overcome a fundamental incompatibility issue with Lactic Acid and could alter the product's feel.
4. Changing Lactic Acid to another acid: Different acids have varying strengths and compatibility profiles. This is another option if pH adjustment is necessary, but also requires testing.

Given that your original formula at pH 7.1 was stable and deemed appropriate by the staff, the recommended course of action is to revert to that formula by removing the Lactic Acid.

Your observation about Lactic Acid being found in shampoos is correct; as the staff mentioned, it's often included there for its hair conditioning benefits, which is a different purpose than pH adjustment and might be compatible with different formulation bases.