Let me ask you a question. About making Vitamin C serum with the following ingredients
1. Vitamin C (SAP) 10%
2. Hyaluronic Acid 0.5%
3. phonoxy ethanol 0.9%
4. L-Glutathione Reduced 1%
5. Disodium EDTA 0.2%
6. Sodium Gluconate 0.2%
7. Xanthan Gum 0.2%
8. Nonapeptide-1 (2500ppm), Water, Phenoxyethanol 1%
But it was found that the sap was unstable at the neck, turning yellow. How should I solve the problem? Please advise.
And another problem that is found is the smell, not sure if it's vit c or not, the smell is quite strong. How can it be solved? I used to use oder kill 1%. The smell is not reduced.
