Serum Formulation Advice

Hello!

It's great that you're interested in making your own serum and have been studying the process. It shows dedication! Let's go through your formula and questions based on your goals and the expert feedback provided.

Review of Your Proposed Formula

Your goal is a hydrating serum with a light, slightly gel-like texture for oily, dehydrated, sensitive, acne-prone skin. Your proposed formula includes:

• Cyclomethicone (39%)
• Silicone Gel (34%)
• Hyaluronic Acid (Nano) (0.5%)
• Aloe Vera Extract (3%)
• Phenoxyethanol (0.5%)
• Polysorbate 20 (7%)
• Distilled Water (16%)

Total Silicone (Cyclomethicone + Silicone Gel) is 73%, and the water phase (Water + Hyaluronic Acid + Aloe Vera + Polysorbate 20) is 26.5% (Phenoxyethanol is 0.5%).

Based on expert advice, there are a few key points to consider:

1. High Silicone Content: A total silicone content of 73% is very high. While silicones provide a nice feel and can form a base, such a high percentage can make it difficult to properly emulsify or incorporate the water phase, potentially leading to instability or separation.
2. Polysorbate 20 as Emulsifier: Polysorbate 20 is generally used to solubilize small amounts of oil in a large amount of water (Oil-in-Water system). It is not suitable for effectively combining a significant water phase into a silicone base (Water-in-Silicone system), which seems to be the direction of your formula due to the high silicone content. This is a major reason why your formula might separate.
3. Active Ingredient Concentration: The total concentration of your main active ingredients (Hyaluronic Acid and Aloe Vera Extract) is 3.5%. While these are good ingredients for hydration and soothing, increasing the total active content to around 10% could provide more significant benefits for your skin concerns (hydration, soothing, potentially oil control or anti-acne ingredients).
4. Aloe Vera Extract and Thickeners: As noted in the expert reply, Aloe Vera Extract contains electrolytes that can interfere with the thickening ability of some gelling agents or emulsifiers, potentially causing the serum to become too liquid.

Addressing Your Questions

1. Is the formula suitable? Based on the composition, particularly the high silicone and the use of Polysorbate 20, this formula as written is unlikely to be stable or achieve the desired texture and clarity. It needs significant adjustments.

2. Must anything be added? Yes, you would need a suitable emulsifier or gelling agent that can effectively incorporate the water phase (containing Hyaluronic Acid and Aloe Vera) into the silicone base and maintain stability and texture. Polysorbate 20 is not appropriate. You might also consider adding other active ingredients beneficial for oily, dehydrated, sensitive, acne-prone skin, such as Niacinamide, Panthenol, or specific anti-acne/soothing extracts, keeping in mind their solubility and compatibility.

3. Should percentages be adjusted? Absolutely. The total silicone percentage should be reduced, ideally below 60%, to improve stability and allow for better incorporation of the water phase. The total active ingredient percentage could be increased to around 10% for enhanced efficacy. The percentage of the emulsifier/gelling agent will depend on the specific ingredient chosen and the desired texture, and may need careful adjustment, especially when incorporating Aloe Vera Extract.

4. Are there other necessary modifications? Yes, the primary modification needed is replacing Polysorbate 20 with an appropriate emulsification system for a silicone-based formula that can handle the water phase and the electrolytes from Aloe Vera. The mixing method will also be crucial – typically, the water phase is slowly added to the silicone phase with mixing when using a W/Si emulsifier or a silicone elastomer gel base.

5. Advice on pH measurement and adjustment:

   • Why measure pH? The pH of your serum is important for skin compatibility (skin is slightly acidic, around 4.5-5.5), product stability, and the effectiveness of certain active ingredients. A pH between 4.5 and 6.5 is generally suitable for facial serums.
   • How to measure: Use a calibrated pH meter or cosmetic-specific pH strips. Standard paper pH strips may not be accurate for all cosmetic formulations.
   • How to adjust: After your serum is fully mixed, measure the pH. If it needs adjustment:
     • To lower pH: Add a very dilute solution of Citric Acid (e.g., 10% solution) drop by drop, mixing thoroughly after each addition, and re-measure until the desired pH is reached.
     • To raise pH: Add a very dilute solution of Sodium Hydroxide (NaOH) or Triethanolamine (TEA) (e.g., 10% solution) drop by drop, mixing thoroughly after each addition, and re-measure until the desired pH is reached.
   • Always adjust pH as the final step.

Suggested Approach

Instead of trying to modify your current formula directly, it would be more effective to start with a base system designed to incorporate a water phase into silicones, such as a silicone elastomer gel (like Silicone Gel (Ultra Clear, Super Silky) or Silicone Gel 9040) or a specific Water-in-Silicone emulsifier. You would then build your formula around this base, carefully incorporating the water phase containing your Hyaluronic Acid and Aloe Vera Extract, adjusting percentages to achieve your desired texture and active concentrations while keeping the total silicone below 60%.

Remember that formulating requires experimentation, especially when combining ingredients that can affect viscosity like Aloe Vera Extract. Start with smaller batches and adjust percentages gradually based on your results.