Understanding Your Oil Blend Formulation

You've created an oil blend containing Vitamin C Ester (Ascorbyl Palmitate), Vitamin E (Tocopheryl Acetate), and Olive Oil. It's understandable that you're experiencing separation, especially when made without heat.

Why Separation Occurs

The primary reason for the separation is the limited solubility of Vitamin C Ester (Ascorbyl Palmitate) in natural oils like Olive Oil. While you're using 8% Vitamin C Ester, its typical solubility in natural oils is much lower, around 0.03-0.12%. When you exceed this solubility limit, the excess Vitamin C Ester cannot remain dissolved and will separate out, often appearing as crystals or a distinct layer upon cooling.

Regarding Heating

Gentle heating can help dissolve the Vitamin C Ester initially. The product description for Vitamin C Ester suggests mixing it into the oil phase at around 70°C for easier incorporation. However, even if dissolved with heat, the Vitamin C Ester will likely recrystallize and separate as the mixture cools back down to room temperature because the concentration (8%) is still far above its solubility limit in oil.

Regarding using a microwave for heating, it's generally not recommended for cosmetic ingredients. Microwaves can cause uneven heating, creating hot spots that could potentially degrade heat-sensitive ingredients like Vitamin E. If you need to heat the oil phase for initial dissolution, a gentle method like using a water bath is preferred for more controlled and even heating.

Vitamin E and Olive Oil are oil-soluble and should mix well together; the separation issue at this concentration is mainly due to the Vitamin C Ester.

How to Achieve Stability

To create a stable oil solution, you would need to significantly reduce the concentration of Vitamin C Ester to within its solubility limit in natural oil (0.03-0.12%).

If you wish to use a higher concentration of Vitamin C Ester, you would typically need to formulate a different product type, such as a cream or lotion, which incorporates an emulsifier to keep the oil and water phases (and the ingredients within them) stably mixed. The previous discussion mentioned using an emulsifier like Satin Cream Maker in a cream formula, which is designed to create stable emulsions containing both oil and water phases.