Cosmetic Formula Discoloration and pH Drop: Water Quality and Process Issues

Regarding your question about the percentages of ingredients and the discoloration issue:

Based on the previous assessment, the ingredients you listed (Perfect-C™, Tranexamic Acid, N-Acetyl-D Glucosamine, Vitamin B3, Repair Activator™, Adenosine Complex) are generally stable and the percentages you are using are within typical usage ranges. These ingredients themselves are unlikely to be the primary cause of the rapid yellowing if formulated correctly.

As the staff previously suggested, the issue is more likely related to external factors such as the purity of the RO water you are using (specifically its TDS level) and your manufacturing process (e.g., whether heat is used during mixing). The observed drop in pH from 5-6 down to 4 also indicates a potential instability issue, which could be linked to the water quality or the processing method.

Therefore, simply changing or removing these specific ingredients or adjusting their percentages might not resolve the discoloration problem if the root cause lies in the water purity or the manufacturing process.

We recommend focusing on the factors identified by the staff:

• Check the TDS of your RO water. As suggested, RO water quality can vary, and high mineral content (high TDS) can cause issues. Using water with a very low TDS (like certain drinking water brands recommended by the staff) is crucial for stable formulations.
• Review your manufacturing process. Ensure that excessive heat is not used during mixing, as heat can accelerate degradation of some ingredients, even generally stable ones.
• Ensure pH stability. While the initial pH was good, the drop indicates instability. Addressing water quality and process may help stabilize the pH.

Regarding your question about 4-butyl Resorcinol and Active Resveratrol™:

• 4-butyl Resorcinol can be prone to discoloration, but as the staff mentioned, this can be prevented by including 0.2% Disodium EDTA in the formula and avoiding impure water. It's also recommended to dissolve it in oil rather than glycols if possible.
• Active Resveratrol™ is stable and does not change color.

In summary, while the ingredients and their percentages seem appropriate, the discoloration issue is most likely due to the quality of the water or the manufacturing process. Addressing these factors is the key to preventing the yellowing.