Waterproofing a Milky Lotion Sunscreen for Prolonged Exposure

Subject: High SPF, Waterproof, Milky Sunscreen Formulation

Thank you for your question regarding a high SPF, waterproof, milky sunscreen formulation suitable for prolonged sun exposure.

Based on the previous discussion, the formula provided using SPF Protect Ultra II (Product ID 1048), Milk Lotion Maker (Product ID 1040), Satin Cream Maker (Product ID 247), Water, and Mild Preserved Eco (Product ID 1001) serves as a good base for a milky lotion texture.

To make this formula waterproof, you will need to incorporate a waterproofing agent. As discussed, the base formula using Milk Lotion Maker and Satin Cream Maker is likely an oil-in-water (O/W) emulsion, which is generally not highly waterproof on its own.

You have two main approaches for waterproofing within the context of modifying this formula:

1. Adding a film-forming agent: This involves adding ingredients like WaterGuard™ Lite (Product ID 287) or WaterGuard™ Ultra (Product ID 1338) to the existing O/W formula. These ingredients create a water-resistant film on the skin. You mentioned that using WaterGuard™ Ultra at 6% felt sticky. WaterGuard™ Lite might offer less stickiness while still providing water resistance. Alternatively, you could try a lower percentage of WaterGuard™ Ultra, keeping in mind that reducing the percentage might decrease the level of water resistance. There is often a trade-off between the degree of water resistance and the potential for stickiness when using film formers.

2. Creating a Water-in-Oil (W/O) emulsion: This involves using an emulsifier like Water-in-Oil EZ™ (Product ID 726) to create a W/O system, where water droplets are dispersed within an oil phase. W/O emulsions are inherently more water-resistant than O/W emulsions. However, this approach would require formulating a new base formula using Water-in-Oil EZ™ as the primary emulsifier, which would likely result in a richer texture compared to a milky O/W lotion. As the staff mentioned, Water-in-Oil EZ™ at 2% might be less sticky than WaterGuard™ Ultra at 6%, but also less waterproof.

Considering your preference for a milky texture and your experience with the stickiness of WaterGuard™ Ultra, modifying the existing formula by adding WaterGuard™ Lite or a lower percentage of WaterGuard™ Ultra might be the most direct way to add water resistance while trying to maintain a milky lotion feel.

To incorporate WaterGuard™ Lite or Ultra into the provided formula:
These ingredients are typically added to the oil phase or the final emulsion depending on the specific instructions for the product. Please refer to the product details page for the recommended method of incorporation.

Regarding the stinging and white cast you experienced with your previous formula (not the one provided in this thread), these issues can arise from various factors, including the type and concentration of UV filters used, other active ingredients, or the overall formulation stability. Ensuring the correct pH and proper emulsification are also crucial for product comfort and appearance.

For prolonged sun exposure, a truly waterproof or very water-resistant formula is important to ensure the sunscreen remains effective even with sweating or contact with water.

We recommend carefully testing any modified formula to ensure it meets your desired texture, feel, SPF level (if you have the means to test), and water resistance properties, and does not cause irritation.