Mixing a Water-in-Oil Sunscreen Formula by Hand

Regarding your question about mixing this sunscreen formula by hand, the formula you provided is:

• Water 44%
• Cyclopentasiloxane (Low-Odor Cyclomethicone) 15%
• Titanium Dioxide 15nm Liquid (Gloss) 25%
• Zinc Oxide 35nm Liquid 15%
• Mild Preserved Eco™ (Preservative-Free) 1%

This formula is designed as a water-in-oil emulsion. The recommended mixing procedure for ingredients like Titanium Dioxide 15nm Liquid and Zinc Oxide 35nm Liquid, especially in this type of emulsion, involves heating the oil/silicone phase (which includes Cyclopentasiloxane, Titanium Dioxide 15nm Liquid, and Zinc Oxide 35nm Liquid) to around 70°C and then gradually adding the water phase while blending continuously.

Creating a stable emulsion and ensuring that the sunscreen particles (Titanium Dioxide and Zinc Oxide) are evenly dispersed throughout the mixture typically requires mechanical stirring or a homogenizer to provide sufficient shear force. Simple hand mixing is generally not adequate to achieve the necessary emulsification and particle dispersion for a stable and effective sunscreen.

Therefore, while you can combine the ingredients, achieving a stable, well-mixed sunscreen with proper sun protection using only hand mixing is unlikely. Proper mixing equipment is recommended for this type of formulation.