Serum Precipitation Issue

The white precipitate that appeared in your serum formulation after a few days is most likely caused by the interaction of Zinc PCA with other ingredients in your formula.

Zinc PCA has specific solubility requirements and is most soluble within a pH range of 4-6. When combined with other ingredients, especially at higher concentrations or in the presence of electrolytes like 4MSK or Aloe Vera Extract, the overall environment of the serum can cause Zinc PCA to become insoluble and precipitate over time.

This aligns with the suggestion you received that Zinc PCA is the probable cause.

To resolve this precipitation issue, it is recommended to remove Zinc PCA from your formulation. If you need the benefits of Zinc PCA, you would need to carefully reformulate, paying close attention to the compatibility and optimal pH ranges of all ingredients used together, including Safe-B3™ (Niacinamide), GlucoBright™ (Acetyl Glucosamine), 4MSK, and Willow Bark Extract, to ensure stability.