Making Physical Sunscreen with Nano Titanium Dioxide and Zinc Oxide

For making sunscreen containing physical sunscreens like nano Titanium Dioxide and Zinc Oxide, which often require the use of ingredients that help them adhere well to the skin, such as silicones which are not water-soluble, here are some guidelines and considerations:

1. What ingredients should help, or how should they be mixed?

Since silicones are not soluble in water, an emulsifier is necessary to mix silicones with the water phase in your formula.

• Using Ready-to-Use Emulsifiers: An easy and convenient method for DIY formulators is to use a ready-to-use emulsifier specifically designed to emulsify silicones with water, such as Light Cream Maker™. According to the information, it can help emulsify silicones with water or oil, with a limitation that the amount of silicone in the formula should not exceed 10%. Using a ready-to-use emulsifier simplifies the cream-making process, eliminating the need for HLB value calculations or high heat.
• Using Other Ingredients: Ingredients like Cetyl Alcohol have also been mentioned as being able to help emulsify water and silicones. However, generally, Cetyl Alcohol is a thickener and emollient that needs to be used with a Cream Maker to emulsify water and oil. Using single ingredients like Cetyl Alcohol or Stearic Acid for emulsification can be complex and requires understanding HLB values and proper mixing techniques, which may be more difficult than using a ready-to-use emulsifier.

2. Which one should be chosen between Cyclomethicone and Dimethicone?

The choice between Cyclomethicone and Dimethicone depends on the desired texture of your sunscreen product.

• Cyclomethicone (e.g., Cyclopentasiloxane): This is a lightweight silicone that evaporates quickly, providing a dry, light, and non-sticky feel on the skin. It is suitable for formulas where a thin, fast-absorbing feel is desired.
• Dimethicone: This is a non-volatile silicone available in various viscosities, from light to heavy. It provides a smoother, more coating feel on the skin and offers a longer-lasting smooth sensation compared to Cyclomethicone. The choice of Dimethicone viscosity (e.g., Dimethicone Light/50 or Dimethicone Medium/350) will affect the perceived richness or lightness of the cream texture.

Therefore, if you prefer a light, non-sticky, fast-evaporating texture, you should choose Cyclomethicone. If you want a smooth, well-coating feel that lasts longer, you should choose Dimethicone.

Additional Recommendations

• Dispersion of Physical Sunscreens: Before incorporating powdered Titanium Dioxide and Zinc Oxide into your formula, they should be well-dispersed in the oil or silicone phase to ensure even distribution in the cream, which affects sunscreen efficacy and product smoothness.
• Using Alcohol: It has been suggested that adding about 3-5% Ethyl Alcohol can help silicones evaporate faster, making the product feel lighter. However, the potential drawbacks of alcohol, such as skin dryness or irritation, should be considered.

I hope this information is helpful for developing your sunscreen formula!