Anhydrous Sunscreen Formula Evaluation and Mixing Guide

Your proposed anhydrous sunscreen formula appears viable and the ingredients are suitable for creating a water and sweat resistant product. The base is primarily silicone, which is excellent for creating a water-resistant film on the skin. The physical sunscreen ingredients, Titanium Dioxide 15nm Liquid and Zinc Oxide 35nm Liquid, are dispersed in silicone and are described as waterproof, further supporting your goal.

Here are the recommended mixing steps using an overhead stirrer:

1. Combine the main silicone base ingredients in a beaker: Silicone Gel Ultra-Clear, Silicone Blender, Titanium Dioxide 15nm Liquid, and Zinc Oxide 35nm Liquid.
2. Gently heat this mixture to around 40-50°C while stirring with the overhead stirrer. This helps reduce the viscosity of the silicone base and significantly improves the dispersion of the liquid sunscreen components.
3. Once the mixture is heated and well-combined, add the PMMA Booster and Beige Iron Oxides Easy Mix. Increase the stirring speed as needed to ensure these powders are fully dispersed and no clumps remain. Continue stirring until the mixture is uniform in color and texture.
4. Allow the mixture to cool down to room temperature while continuing to stir slowly. This helps maintain homogeneity as the viscosity increases upon cooling.
5. Once cooled, add the Mild Preserved Eco™. Stir until it is fully incorporated into the formula.
6. Continue stirring for a few more minutes to ensure everything is completely homogeneous before packaging.

Regarding heating, while it might not be strictly necessary if your overhead stirrer is very powerful and can handle the viscosity and disperse powders effectively at room temperature, gently heating the silicone phase (Step 2) is highly recommended. Heating helps to lower the viscosity temporarily, allowing for much better and more uniform dispersion of the physical sunscreen liquids, iron oxides, and PMMA Booster. This leads to a more stable and aesthetically pleasing final product with potentially better UV protection performance due to even filter distribution. The recommended temperature of 40-50°C is well below the limit for Mild Preserved Eco™, which is added after cooling.

With careful mixing using your overhead stirrer, you should be able to achieve a successful anhydrous, water and sweat resistant sunscreen.