Advice for Water-Free Vitamin C Serum Formulation

Based on your formula containing Ethoxydiglycol, Butylene Glycol, 15% L-ascorbic acid, and glycerin, and your goals to reduce the pH from 5 to 3.5, thicken the serum, and improve its feel:

1. Reducing pH in a Water-Free Formula

The staff pointed out that a 15% concentration of L-ascorbic acid should result in a significantly lower pH than 5, even in a water-free system. They suggest that the measured pH of 5 might indicate an issue with the formulation process itself.

• Recommendation: It is highly recommended to re-check your formula, the accuracy of your weighing, and the mixing steps before attempting to adjust the pH with other ingredients.
• Measuring pH: Measuring pH directly in a water-free formula is complex. The suggested method is to dilute your serum with water (e.g., 50% serum + 50% water) and measure the pH of the diluted solution. This provides a more practical pH value relevant to skin application.

If, after re-checking your process and measuring the diluted formula, the pH is still unexpectedly high, you may need to review the raw materials or formulation method.

2. Thickening and Smoothing the Serum

The staff recommended the following ingredients:

• For thickening: Add Pro Polymer (Acrylate Crosspolymer) to your formula.
• For smoothing: After thickening, you can improve the feel by adding a powder such as SiliSilk (Silicone powder) or AminoSilk (Lauroyl Lysine), typically around 3%.