Sunscreen: Overall Formulation Strategy

Water resistance isn't just about adding specific ingredients—it's about overall formulation strategy

Emulsion Type: The majority of sunscreens are emulsions: drops of oil suspended in water (O/W) or drops of water suspended in oil (W/O). Water-in-oil (W/O) emulsions are inherently more water-resistant than oil-in-water formulations because they use water-insoluble emulsifiers. This structure prevents loss through water contact more effectively. However, W/O emulsions typically feel heavier on the skin, creating a formulation challenge when aiming for products people will enjoy using. Burnd is expert at the use of W/O technology to create truly elegant sunscreens. 

Reduced Emulsifier Levels: Using the minimum amount of emulsifiers necessary helps prevent re-emulsification when the sunscreen contacts water or sweat. Fewer emulsifiers can also reduce the chance of eye stinging when sunscreen migrates due to sweating.

Alcohol-Based Systems: Some high performance, water resistant formulas use alcohol to dissolve film-forming polymers. As the alcohol evaporates, these polymers precipitate and form a water-resistant film on the skin.

Anhydrous Formulations: Products with little or no water are inherently more resistant to being washed away by external water, but formulators must work hard to ensure they don't feel too heavy. These are also often hard to apply and they inadvertently encourage underapplication.