Begin by combining the propanediol and salicylic acid in a heat-safe container. Heat gently in a water bath and stir until the salicylic acid is fully dissolved, then allow this mixture to cool to below 40°C before use.
In a separate container, add niacinamide to the distilled water and mix until fully clear. Once dissolved, add the hyaluronic 1% solution, vegetable glycerine, and phenoxyethanol preservative, then stir well until evenly combined.
Slowly add the cooled salicylic acid solution into the water phase and mix thoroughly. The final result should be a clear, lightweight gel serum.
Check and adjust the pH as this is a critical step. The target pH is 4.0 to 4.5. Use the 10% dilution method by mixing 1g serum with 9g distilled water, then test. If needed, lower the pH with a 10% citric acid solution or raise it with a 10% baking soda solution, adding drop by drop and re-testing until the correct range is reached.
Safety & Usage
Use 2–3 times per week to build tolerance. Always apply SPF during the day. Avoid use if allergic to aspirin, and do not apply to broken or irritated skin.
Perfect For
Acne-prone skin, oily and combination skin, and texture or post-acne marks.
