Addressing Pilling in Your Sunscreen Formulation

The issue you're experiencing with your sunscreen formulation pilling or flaking off the skin is common, especially with formulas containing a high percentage of physical sunscreens like Zinc Oxide.

Based on your formula (Water 50%, LipidSoft 20%, Zinc Oxide 25%, Light Cream Maker 1%, Mild Preserved Eco 1%, 1,2-Hexanediol 3%), here are the likely causes and potential solutions:

Potential Causes of Pilling

• High Zinc Oxide Concentration: At 25%, Zinc Oxide is a significant solid component. If the particles are not perfectly dispersed and stabilized within the formula, they can sit on the skin surface and rub off, causing pilling.
• Emulsifier Limitations: Light Cream Maker is an effective emulsifier but is noted to handle up to 20% oil. Your formula contains 20% LipidSoft and 25% Zinc Oxide. While Zinc Oxide isn't oil, it's a solid dispersed phase that adds to the complexity and load on the emulsifier system. This high dispersed phase percentage might exceed the capacity of Light Cream Maker, leading to instability and pilling.
• Insufficient Dispersion/Mixing: The description for Light Cream Maker mentions that insufficient blending or stirring can result in a flaky texture when applied. Proper dispersion of Zinc Oxide is also crucial; if the particles clump together, they will pill.
• Ingredient Interactions: The combination of ingredients, including the specific type of LipidSoft used and the presence of 1,2-Hexanediol, can influence the final film formed on the skin and its tendency to pill.

Recommended Solutions

To reduce or eliminate pilling, consider the following adjustments:

1. Improve Zinc Oxide Dispersion: This is often the most critical factor. Instead of using a powder form of Zinc Oxide, consider switching to a pre-dispersed liquid form. Products like Zinc Oxide Transparent Dispersion (C12-15 alkyl benzoate Base), Zinc Oxide Transparent Dispersion (Isopropyl Palmitate Base), or Zinc Oxide 40nm Dispersion (Water Base) provide Zinc Oxide particles that are already finely dispersed and easier to incorporate smoothly into your formula, significantly reducing the likelihood of pilling. You would need to adjust the percentage based on the active Zinc Oxide content of the dispersion.
2. Optimize Mixing Procedure: Ensure you are mixing the formula thoroughly, especially when incorporating the Zinc Oxide and emulsifying with Light Cream Maker. Follow the recommended mixing instructions for Light Cream Maker carefully, ensuring sufficient blending to create a smooth, stable emulsion.
3. Review Emulsifier System: Given the high dispersed phase (oil + solid Zinc Oxide), you might need to explore emulsifier systems designed to handle higher solid loads or consider using a co-emulsifier to enhance stability and prevent pilling. While increasing Light Cream Maker slightly might help with viscosity, it may not resolve the pilling caused by the high solid content.
4. Consider LipidSoft Type: The specific LipidSoft used can affect the feel and spreadability. Lighter, more spreadable emollients like LipidSoft CC or LipidSoft Cyclo, or emollients commonly used in sunscreens like LipidSoft B, might contribute to a smoother application and less pilling compared to heavier options.

By focusing on improving the dispersion of Zinc Oxide and ensuring your emulsifier system can effectively handle the high solid content, you should be able to significantly reduce or eliminate the pilling issue in your sunscreen formulation.