Adjusting Sunscreen Texture for Fluidity

Your current formula uses Silicone Gel (Ultra Clear), which is a silicone elastomer gel. This type of ingredient is excellent for providing a smooth, silky feel and increasing spreadability, but it also contributes significantly to the viscosity and gel-like texture you are experiencing.

1. Replacing Silicone Gel with Cyclopentasiloxane

Yes, replacing Silicone Gel (Ultra Clear) with Cyclopentasiloxane will definitely help make your sunscreen texture more fluid. Cyclopentasiloxane is a lightweight, volatile silicone fluid with a low viscosity (5-9 mPa.s). It provides a soft, smooth feel and evaporates quickly, contributing to a lighter skin feel compared to a gel.

To achieve a more fluid texture, you will need to replace a significant portion, or potentially all, of the Silicone Gel with Cyclopentasiloxane. Your current formula uses 28% Silicone Gel. You could try replacing 15-25% of the Silicone Gel with Cyclopentasiloxane initially and adjust based on the resulting texture. For example, you could try a formula with 10% Silicone Gel and 18% Cyclopentasiloxane, or even 0% Silicone Gel and 28% Cyclopentasiloxane, adjusting the water percentage accordingly to keep the total at 100%.

• Recommendation: Start by replacing half (around 14%) or more of the Silicone Gel with Cyclopentasiloxane. The exact percentage will require some experimentation to get the desired fluidity while maintaining stability.

2. Using Silicone Blender with Cyclopentasiloxane

Your current formula is a water-in-oil (W/O) emulsion, which is indicated by the use of Titanium Dioxide 15nm Liquid and Zinc Oxide 35nm Liquid, as these are designed for W/O systems. Silicone Blender acts as a coupling agent for different silicones and can help stabilize silicone-in-water or water-in-silicone emulsions.

Since your formula contains both a silicone/oil phase (Cyclopentasiloxane, the silicones in the TiO2/ZnO dispersions, PMMA Booster, Beige Iron Oxides EasyMix™) and a water phase, Silicone Blender is likely playing a role in stabilizing this W/O emulsion.

Therefore, even if you replace Silicone Gel with Cyclopentasiloxane, you will likely still need Silicone Blender to help maintain the stability of your water-in-oil emulsion.

• Recommendation: Continue to use Silicone Blender in your formula. The current percentage of 3% is within the recommended usage rate (2-5%) and should be appropriate for helping to stabilize the emulsion with Cyclopentasiloxane.

3. Water Resistance with Cyclopentasiloxane

The water resistance of your sunscreen formulation primarily comes from the nature of the emulsion system (water-in-oil) and the film-forming properties of the silicones and the dispersed physical filters (Titanium Dioxide and Zinc Oxide). Water-in-oil emulsions create a continuous external phase of oil/silicone, which repels water effectively.

Both Titanium Dioxide 15nm Liquid and Zinc Oxide 35nm Liquid are specifically developed for water-in-oil systems and are described as being able to provide water resistance. Cyclopentasiloxane is a silicone fluid and is compatible with the oil/silicone phase of your emulsion.

Replacing Silicone Gel with Cyclopentasiloxane should not negatively impact the water resistance, provided that the overall water-in-oil emulsion remains stable. The key to maintaining water resistance is ensuring the W/O structure is intact and forms a continuous hydrophobic film on the skin.

• Recommendation: Using Cyclopentasiloxane instead of Silicone Gel should not reduce the water resistance of your sunscreen, as long as the water-in-oil emulsion remains stable. Ensure proper mixing and consider the role of Silicone Blender in maintaining this stability.

In summary, replacing Silicone Gel with Cyclopentasiloxane is a good approach to reduce the viscosity and achieve a more fluid texture. You should continue using Silicone Blender to help stabilize the water-in-oil emulsion, and this change should not compromise the water resistance of your formulation. Remember to adjust the water percentage to keep the total formula at 100% when changing silicone percentages, and always perform stability testing on your modified formula.