Using L-Ascorbic Acid Powder in Water-Based Formulas

Regarding your questions about using L-ascorbic acid powder:

1. Can L-ascorbic acid powder be mixed directly with water and applied to the face?
   L-ascorbic acid powder should not be mixed directly with plain water and applied to the face. L-ascorbic acid is highly unstable when dissolved in water and will oxidize and degrade quickly, losing its effectiveness. This is a key limitation of L-ascorbic acid in water-based solutions.

2. If mixing with a toner or essence that contains water, what ingredients should or should not be present?
   Mixing L-ascorbic acid powder into a pre-made water-based toner or essence is generally not recommended due to the stability issues mentioned above. The stability of L-ascorbic acid in a water-based formula depends heavily on several factors that are difficult to control when using a pre-made product:

   • pH Level: L-ascorbic acid requires a low pH (typically between 2.0 and 4.0, with 3.5-4.0 being suitable for skin) to remain stable. Most toners or essences have a higher pH, which would cause rapid degradation of L-ascorbic acid.
   • Presence of Metal Ions: Metal ions like iron, copper, and nickel can catalyze the oxidation of L-ascorbic acid in water. A good L-ascorbic acid formula in water should include a chelating agent like Disodium EDTA to bind these metal ions.
   • Presence of Stabilizers: Ingredients that help protect L-ascorbic acid from oxidation and UV light are beneficial. These can include other antioxidants (like Vitamin E and Ferulic Acid) and specific UV protectors.

   Since you cannot guarantee the correct pH, the presence of chelating agents, or sufficient stabilizers in a pre-made toner or essence, mixing L-ascorbic acid powder into such products will likely result in a rapidly degrading and ineffective serum.

   For stable Vitamin C in water-based formulas, consider using more stable derivatives like:

   • Ethyl Ascorbic Acid
   • Ascorbyl Glucoside
   • Magnesium Ascorbyl Phosphate (MAP)
   • Sodium Ascorbyl Phosphate (SAP)

   If you wish to use L-ascorbic acid, it is best to formulate a serum from scratch where you can control all the necessary parameters for stability, or use it in anhydrous (water-free) formulations like silicone-based serums, which is suitable for the Ultra-Fine grade of L-ascorbic acid.