Recommendations for Improving Sunscreen Lotion Formulas

Regarding your questions about improving existing lotion formulas and making waterproof formulas, here are some recommendations:

Adding SPF Ingredients Directly to Existing Lotion

Adding SPF ingredients directly into your existing lotion is not recommended. Cosmetic formulas are complex, and adding new ingredients can lead to instability, separation, or unpredictable SPF efficacy. This is because each sunscreen ingredient has different solubility and compatibility with other components. Furthermore, determining the actual SPF value of a newly mixed product requires specific testing.

Making Sunscreen Lotion Waterproof

Waterproof properties in sunscreen products often come from the use of Film Formers. These ingredients create a thin film layer on the skin, helping the sunscreen adhere better even when exposed to water or sweat.

Common film formers used in sunscreen formulas for water resistance include:

• WaterGuard™ Spray (Acrylates / Octylacrylamide Copolymer): A polymer that creates a durable film, suitable for use in sunscreen formulas to make them waterproof/sweat resistant.
• UV35 (Polyurethane-35): A film former designed to be water-resistant and can also help boost SPF efficacy.
• Allianz OPT (Acrylates/C12-22 Alkyl Methacrylate Copolymer): A polymer that helps sunscreen formulas be more durable and resistant to water and sweat, suitable for low-viscosity formulas.

In addition to film formers, for Physical Sunscreens (like Zinc Oxide, Titanium Dioxide) in Water-in-Oil (W/O) formulas, increasing the viscosity of the oil phase, such as by using Waxes like Beeswax, can also help improve skin adherence and provide a degree of water resistance.

Adding Emulsifier to Water-Based Sunscreen for Thickening

Emulsifiers primarily function to help oil and water mix together into a stable emulsion. They are not typically used as the main ingredient for thickening water-based formulas directly.

If you want to increase the viscosity of your existing water-based sunscreen, you should use a Thickener specifically designed for thickening water-based formulas. These are usually polymers that dissolve or disperse well in water.

For water-dispersible sunscreen ingredients like the AquaForce™ series (e.g., AquaForce™ BEMT, AquaForce™ DHHB), they disperse well in water, allowing for the development of sunscreen formulas with a light, non-sticky texture. However, these ingredients do not primarily function as thickeners themselves.

Hope this information is helpful.