Shelf Life of Preservative/Formula and Calculating Glycolic Acid % by Weight

Hello,

Regarding your questions about mixing Witch Hazel and AHA, and the formulation:

1. Can Witch Hazel and AHA be mixed? Yes, Witch Hazel and AHA can be used together in a formulation.
2. Proportions for a similar product: The staff mentioned that the product you referenced uses Glycolic Acid at 5%. They provided an example formula for a tonic base:
   • Glycolic Acid: 5%
   • Witch Hazel: 90%
   • Propylene Glycol: 5%
   • Mild Preserved Eco (Preservative): 1%
     
     (Note: The original question mentioned Lactic Acid, but the staff's example uses Glycolic Acid)
3. Shelf life based on preservative: The 60-day mention for the preservative refers to the recommended usage period for the small packaging size after opening, not the shelf life of the ingredient itself or the final formula. The actual shelf life of the ingredient is stated on its label and the website, varying by lot. For the shelf life of a finished formula, please refer to the link provided by the staff: http://www.myskinrecipes.com/topic171.html.
4. Measuring Glycolic Acid by volume (ml) with a scale: Formulations are typically done by weight (%). Using a scale to measure percentage by weight is the standard method. To understand the basics of mixing and calculations, including how to work with percentages by weight, please read the beginner's guide linked by the staff: http://www.myskinrecipes.com/topic174.html.

Hope this clarifies your questions!