Ingredients for W/Si Physical Sunscreen Foundation

In a Water-in-Silicone (W/Si) physical sunscreen formulation, the "foundation" or continuous phase is the silicone phase. The key ingredients for this phase provide the structure, texture, and stability of the emulsion, and help disperse the physical sunscreen powders (like Zinc Oxide and Titanium Dioxide).

Here are some types of ingredients suitable for the silicone continuous phase and forming the W/Si emulsion:

• Silicone Gels/Elastomers: These are often pre-dispersed silicone elastomers in a silicone fluid (like Cyclopentasiloxane or Dimethicone). They are excellent for building viscosity in the silicone phase, providing a smooth, powdery, and non-greasy feel, and helping to suspend pigments and powders. Examples include Silicone Gel 9040 (e.q. DC 9040, Cyclopentasiloxane Base) and Silicone Gel 5041 (e.q. BSG-5041, Dimethicone Base).
• Silicone Elastomer Powder: This is the solid elastomer itself, which needs to be dispersed in a suitable silicone fluid. It provides similar benefits to the silicone gels, such as thickening, oil absorption, and a matte finish. An example is Silicone Elastomer Powder.
• Silicone Phase Thickeners/Stabilizers: Ingredients like Oil-Fix™ W (Oil/Silicone, Silica Dimethyl Silylate) can help thicken the silicone phase, improve emulsion stability, enhance waterproof properties, and provide a matte texture.
• W/Si Emulsifiers: These are crucial for creating and stabilizing the water-in-silicone emulsion, allowing the water phase to be dispersed within the continuous silicone phase. Examples include Polyglyceryl-4 Isostearate and Polyglyceryl-2 Triisostearate.
• Texture Enhancers: Ingredients like SiliSilk™ WO (Water/Oil Dispersible Silicone Powder) can improve the feel of the final product, offering softness and oil absorption, and are dispersible in the silicone phase.

By combining these types of ingredients, you can create a stable and pleasant-feeling W/Si physical sunscreen base that effectively disperses UV filters and provides desired sensory properties.