Water-Free Vitamin C Formula, pH Measurement, and Adding AHA
Question
I have formulated a water-free Vitamin C product with the following composition:
- Silicone Gel: 50%
- Isododecane: 30%
- L-Ascorbic Acid Ultra-Fine: 15%
- Ascorbyl Palmitate: 5%
I have a few questions regarding this formula:
- Is using 30% Isododecane acceptable in this water-free formula?
- How can I measure the pH of this water-free formula?
- Can I add 8% AHA to this formula? What would be the effect?
Answer
Water-Free Vitamin C Formula and pH Measurement
Regarding your water-free Vitamin C formula using 50% Silicone Gel, 30% Isododecane, 15% L-Ascorbic Acid Ultra-Fine, and 5% Ascorbyl Palmitate:
Isododecane Concentration: Using 30% Isododecane is generally acceptable in an anhydrous (water-free) formula like this. The base composition (Silicone Gel and Isododecane) primarily acts as a solvent and delivery system for the Vitamin C powders.
pH Measurement: As discussed in the conversation, you cannot accurately measure the pH of a water-free formula using litmus paper or a standard pH meter. pH is a measure of the acidity or alkalinity of water-based solutions. Since your formula contains no water, the concept of pH as typically measured does not apply.
Stability: A key advantage of water-free Vitamin C formulas (especially with L-Ascorbic Acid) is their inherent stability. L-Ascorbic Acid degrades rapidly in the presence of water. By formulating without water, you significantly reduce the risk of oxidation and degradation, making pH adjustment unnecessary for stability.
Adding AHA: It is strongly not recommended to add 8% AHA to this formula. Combining 15% L-Ascorbic Acid with 8% AHA would result in a product with a very high total acid concentration. Such a high level of acidity (even if pH isn't conventionally measurable) is likely to cause significant skin irritation, redness, burning, peeling, and potentially damage the skin barrier, especially in a leave-on product. High concentrations of acids like this are typically only used in controlled, short-contact professional peel treatments.
If AHA was added: If you have already added 8% AHA, the formula would become excessively acidic and potentially harmful for use as a regular leave-on serum. It is advisable not to use this batch on your skin due to the high risk of adverse reactions.
In summary, your water-free formula is stable because it lacks water, and pH measurement is not applicable. Do not add AHA as it will make the product too acidic and irritating for the skin.
