Salicylic Acid Precipitation in Serum/Solution
Question
I am formulating a serum/solution containing Salicylic Acid, Propylene Glycol, Tween 20, and water. I am experiencing precipitation in the formula. I have tried a simplified version with just these four ingredients and still observe precipitation. What could be causing this precipitation, and how can I prevent it?
Answer
Subject: Precipitation Issue Resolved
Hello,
Thank you for sharing your detailed troubleshooting process.
Based on the conversation, the initial formula had potential issues with:
- Alpha Lipoic Acid (ALA): This ingredient is not easily water-soluble and is best used in a cream base. It tends to precipitate in water-based formulas unless high levels of specific solubilizers are used.
- Zinc PCA: This ingredient can be sensitive to higher pH levels (neutral to slightly alkaline) and might become unstable. Adding it after combining the main phases was suggested as a potential solution.
Through your testing with simpler formulas, you identified that the precipitation occurred even with just Propylene Glycol, Tween 20, Salicylic Acid, and water.
You concluded that the most likely cause of the precipitation was insufficient solubilization of Salicylic Acid by Tween 20 due to rushing the mixing process. Allowing enough time and ensuring thorough mixing of Salicylic Acid with Tween 20 in the Propylene Glycol phase before adding the water phase is crucial for proper solubilization and preventing precipitation.
We are glad to hear you were able to resolve the issue by adjusting your mixing technique.