Comparison of Vitamin C Serums and Increasing Concentration

Based on the staff's response:

1. Difference and Effectiveness: The two products, Stabilized Vitamin C (Natural-C Glycol™) Serum (ID 486) and Vitamin C E Ferulic Pre-Mix Kit (Lite) (ID 70), work similarly. The main difference lies only in the method used to stabilize the Vitamin C and prevent its degradation. The staff response does not indicate that one is significantly more effective than the other or suitable for different problems; they function in a similar way.
2. Increasing Concentration: You cannot simply add more Vitamin C (L-Ascorbic Acid Ultra Fine) powder (ID 133) to either serum to increase the concentration to 20%. The staff advises against this. They also note that if 15% concentration did not show results, increasing to 20% is unlikely to make a significant difference, as ingredient effectiveness can vary greatly from person to person. They suggest exploring other ingredients with similar benefits if Vitamin C is not effective for your skin.