Vitamin C Serum Comparison and Concentration Adjustment

Regarding the two Vitamin C serums you mentioned:

• Stabilized Vitamin C (Natural-C Glycol™) Serum (15%)
• Vitamin C E Ferulic pre mix kit

Both formulations use L-Ascorbic Acid, which is the most effective form of Vitamin C for skin absorption and stimulating collagen production. Therefore, their ability to be absorbed and promote collagen synthesis should be similar.

Regarding your question about increasing the concentration to 20%:

The Stabilized Vitamin C (Natural-C Glycol™) Serum is a ready-to-use product formulated for stability. The product description explicitly states that it is not suitable for mixing any additional ingredients as this may affect the stability of the Vitamin C. Adding more Vitamin C is not recommended.

The Vitamin C E Ferulic pre mix kit is also designed as a specific formulation. Modifying pre-mixed kits by adding additional active ingredients like Vitamin C is generally not recommended as it can disrupt the balance and stability of the formula, potentially reducing its effectiveness or causing irritation.

Since modifying these products by adding more Vitamin C is not advised due to stability and efficacy concerns, we cannot provide a calculation for the cost of increasing the concentration to 20%. It is best to use these products as formulated or look for a product that is already at your desired 20% concentration.

If you are looking for a 20% Vitamin C product, you might consider searching for other available options that are formulated at that concentration.