White Residue in Vitamin C Serum

Vitamin C Serum Residue Issue

The white, powdery residue you are seeing after the serum dries is likely caused by either:

1. Undissolved L-ascorbic acid: At 15%, L-ascorbic acid is a high concentration. If it doesn't fully dissolve in the liquid phase, the crystals can become visible as the serum dries on the skin.
2. Improperly hydrated thickener (AnyGel / Dehydroxanthan Gum): Gum thickeners need to be properly dispersed and hydrated. If not, ungelled particles can remain and leave a residue upon drying. This is a very common cause of this type of issue.

Recommendations:

• Ensure L-ascorbic acid is fully dissolved: Add L-ascorbic acid to the water phase and stir until completely clear before adding other ingredients. Gentle warming of the water can help, but cool before adding other components.
• Properly hydrate the thickener: This is crucial. Do not add the powder directly to the bulk liquid.
  • Disperse the AnyGel in a small amount of Propylene Glycol or Ethoxydiglycol first to make a slurry, then add this slurry to the water phase while stirring vigorously.
  • Alternatively, if adding directly to water, sprinkle the powder very slowly into the vortex of rapidly stirred water.
  • After adding, stir well and let the mixture sit for 15-30 minutes to allow the gum to fully hydrate before continuing.
• Check your mixing process: Since this issue is new, review your steps to see if anything changed, especially how you added the thickener.

Focusing on ensuring both the L-ascorbic acid is fully dissolved and the AnyGel is properly hydrated should resolve the white residue problem. The pH you measured is appropriate for the serum.