Addressing White Cast and Dryness in Your Sunscreen Formula

It sounds like you've created a physical sunscreen formula, and it's common to experience white cast and dryness, especially with high percentages of Titanium Dioxide and Zinc Oxide. Here are some ways to modify your formula to improve these issues:

Reducing White Cast

The white cast is caused by the physical nature of Titanium Dioxide and Zinc Oxide particles reflecting light. To minimize this:

• Use Transparent or Treated Physical Filters: Consider replacing some or all of the standard Titanium Dioxide 15nm Liquid and Zinc Oxide 35nm Liquid with transparent or specially treated versions. Products like Titanium Dioxide Transparent (15nm, Water-Dispersion) or Zinc Oxide Transparent Dispersion (C12-15 alkyl benzoate Base) are designed to offer UV protection with significantly less visible white residue. You would need to adjust the percentages to achieve the desired SPF/PA protection, as the active content might differ.
• Incorporate Pigments: For darker skin tones, adding a small amount of cosmetic-grade iron oxide pigments can help counteract the white cast and blend better with the skin tone. You can use a blend of Iron Oxides Red, Iron Oxides Yellow, and Iron Oxides Black, or use a pre-mixed Iron Oxides Brown. Start with very small amounts (e.g., 0.1-0.5%) and adjust until the desired tint is achieved. Ensure the pigments are compatible with your formula base (oil/silicone dispersible).

Improving Dryness

Physical sunscreens can sometimes feel dry on the skin. To improve the feel and add moisture:

• Increase Emollients: You can increase the percentage of the oil/silicone phase, such as Cyclopentasiloxane (Low-Odor Cyclomethicone), or add other emollients. Consider incorporating ingredients like LipidSoft™ Palm, LipidSoft™ Moist, or Squalane Oil Gel. These can improve spreadability, reduce the dry feel, and provide a smoother finish. You might need to slightly reduce the water phase to accommodate the added emollients.
• Add Humectants: Humectants help draw moisture into the skin. While your formula is water-based, adding effective humectants can boost hydration. Consider adding ingredients like MOIST24 or MOIST72™ in the water phase. Start with a small percentage (e.g., 1-5%) and see how it affects the skin feel.

Remember that any changes to the formula will require re-testing for stability and sun protection efficacy (SPF/PA) if you aim for a specific claim. Start with small adjustments and observe the results.