Pure EGCG and L-Ascorbic Acid Booster

You've observed that your formula containing Pure EGCG turned darker over time, and this is likely due to the degradation or reaction of the Pure EGCG, as previously discussed. While using Pure EGCG at concentrations higher than 2% is not considered harmful, it does not offer increased efficacy beyond this level. The benefit plateaus at 2%, so using more would not provide additional skin benefits.

Regarding your idea of mixing Pure EGCG and L-ascorbic acid powders together to use as a daily booster: both Pure EGCG and L-ascorbic acid are sensitive to environmental factors like light, air, and moisture, especially L-ascorbic acid which is known to be unstable when dissolved in water. Pre-mixing the powders and storing them, even in a light-protected container, could potentially lead to a decrease in their stability and efficacy over time due to potential interactions or exposure to residual moisture/air each time the container is opened.

For optimal stability and effectiveness of both Pure EGCG and L-ascorbic acid, it is best to store them separately in their recommended conditions (typically cool, dark, and airtight). When you want to use them as a booster, it is recommended to mix the desired small amount of each powder with your serum immediately before application. This method ensures that the ingredients are in their most active form when applied to your skin, maximizing their benefits.