Troubleshooting Liquidity in Acne Gel with Zinc PCA and Cosmedia SP

The reason your gel formulation is liquid is due to a chemical incompatibility between your thickener and your active ingredients:

1. Electrolyte Sensitivity of Cosmax™ SP (Sodium Polyacrylate): This ingredient is an anionic polymer that is extremely sensitive to electrolytes (salts). Zinc PCA is a salt that releases zinc ions, which cause the polymer chains of Cosmax™ SP to collapse, instantly turning the gel into a liquid.
2. pH Conflict: Cosmax™ SP requires a pH between 6-12 to thicken effectively. However, Zinc PCA and Complex Salicylic Acid are most stable and effective at a lower pH (around 4-6). At this lower pH, Cosmax™ SP cannot maintain its viscosity.

How to Fix the Formulation:

1. Switch to an Electrolyte-Resistant Thickener (Recommended):
The most effective solution is to replace Cosmax™ SP with a thickener that can handle salts and low pH.

• Increase Hydroxyethyl Cellulose (HEC): Increase the concentration of HEC to 1.2% - 1.5%. HEC is non-ionic and resistant to electrolytes, making it ideal for formulas containing Zinc PCA.
• Add Xanthan Gum: Using Xanthan Gum (Clear Gel Type) at 0.3% - 0.5% in combination with HEC can improve the texture and stability of the gel.

2. Proper Mixing Technique for HEC:
HEC requires heat to hydrate properly. You should heat the water to approximately 70°C and stir continuously while slowly adding the HEC powder until it forms a clear gel.

3. Adjust the pH:
Ensure the final pH of your formula is between 5.0 - 5.5. This range is optimal for the stability of both Zinc PCA and Salicylic Acid.

Suggested Adjusted Formula:

• Hydroxyethyl Cellulose (HEC): 1.5% (Main thickener)
• Complex Salicylic Acid (Powder, Water-Soluble): 1.5%
• Vitamin B3 (Safe-B3™): 4.0%
• Zinc PCA: 1.0%
• Pep®-Acne (Oligopeptide-10): 0.5%
• Centella Asiatica Extract: 2.0%

• Water: to 100%

• Note: Remove Cosmax™ SP from the formula as it is not compatible with Zinc PCA.*