Formulating a Stable L-Ascorbic Acid (Vitamin C) Serum (15-20%) and Mixing Limitations

Hello,

I understand you want to make a 15-20% Vitamin C serum using L-ascorbic acid, Ethoxydiglycol, and Ferulic Acid, and you're asking if you can mix it with your current Hada Labo product.

As the staff mentioned, pure L-ascorbic acid (powder form) has limitations regarding solubility and stability. It cannot be mixed directly into general water-based products like your Hada Labo lotion. Doing so will cause the vitamin C to degrade quickly, lose effectiveness, and may not dissolve completely.

To make an effective and stable L-ascorbic acid serum, you need a specific formulation and pH adjustment to the optimal range (around 2.5-3.5), which requires a pH meter to check.

Here is a basic formulation for making a 15% L-ascorbic acid serum (30ml) using the ingredients you have. (This formula should be made separately, not mixed with Hada Labo).

Ingredients (for 30ml):

• L-ascorbic acid (powder): 4.5 grams (For 20%, use 6 grams, but it may be more irritating)
• Ethoxydiglycol: 1.5 grams (5%)
• Ferulic Acid: 0.15 grams (0.5%)
• Distilled Water or Deionized Water: Approximately 23.85 grams
• pH Adjuster (e.g., low concentration Sodium Hydroxide solution): A small amount needed to adjust pH (Essential to have and requires a pH meter)

Instructions:

1. Dissolve Ferulic Acid in Ethoxydiglycol. Stir well until dissolved.
2. Dissolve L-ascorbic acid in Distilled/Deionized Water. Stir until completely dissolved.
3. Combine the solutions from step 1 and 2. Stir to mix.
4. Very Important: Use a pH meter to measure the pH of the serum. Slowly add the pH adjuster drop by drop (e.g., 10% Sodium Hydroxide solution), stirring and measuring the pH until it is in the range of 2.5 - 3.5.
5. Transfer the serum into a dark, airtight bottle.

Important Notes and Recommendations:

• pH adjustment is the most critical step for Vitamin C efficacy and stability. If you do not have a pH meter and a pH adjuster, it is not recommended to make this formula.
• Homemade L-ascorbic acid serums are generally unstable and degrade quickly. Store in the refrigerator in a dark bottle and use within 1-3 months. Observe the color; if it turns dark yellow to orange, it is starting to degrade.
• You can use your existing Hada Labo product separately to help hydrate your skin.

Hope this information is helpful.