Formulation Feedback: Lightweight Physical Sunscreen SPF 50+ PA++++

Thank you for sharing your physical sunscreen formulation designed for prolonged outdoor exposure under strong sun, with an emphasis on a lightweight feel for reapplication. Here is an evaluation of your formula and answers to your questions:

Formula Evaluation

Your formula incorporates a robust combination of physical UV filters (Zinc Oxide and Titanium Dioxide) at high concentrations, along with SPF/PA boosters and ingredients aimed at improving texture, oil control, and skin benefits. The use of a water-in-oil/silicone emulsifier (Warp Cream Maker XL) and lightweight emollients (LipidSoft Lite, Dimethicone Light) is appropriate for creating a formula that is more water-resistant and feels lighter than traditional physical sunscreens.

Ingredients like SelectSorb and Hydroxyapatite are excellent additions for absorbing excess oil and providing a smoother, less greasy feel, which is crucial for reapplication and comfort, especially in dusty environments.

Answers to Your Questions

1. SPF and PA Estimation: Based on the inclusion of 20% Zinc Oxide 35nm Liquid, 10% Titanium Dioxide 15nm Liquid, and 5% PMMA Booster, your formula is expected to achieve SPF 50+ and PA++++ protection. The high concentration of physical filters combined with the boosting effect of PMMA Booster (which can significantly increase SPF/PA values) makes this level of protection highly probable. For precise SPF and PA values, laboratory testing is required. The company offers a free SPF measurement service when using PMMA Booster in your formulation.

2. Antioxidant Effectiveness and Stability: Yes, the antioxidants and beneficial actives in your physical sunscreen formula can still be effective. While physical filters form a surface barrier, the emulsion base is in contact with the skin, allowing these ingredients to exert their effects. Furthermore, these antioxidants (Ectoin, PolyProtect, Ethyl Ferulate, Licochalcone A, Carnosine, Gamma Oryzanol) play a vital role in protecting the sunscreen formulation itself from degradation caused by UV exposure and oxidation, helping to maintain its efficacy and shelf life. Ethyl Ferulate and Gamma Oryzanol are oil-soluble antioxidants, while Ectoin, Licochalcone A, and Carnosine are water-soluble, offering protection to both phases of your emulsion. The inclusion of Mild Preserved Eco provides microbial preservation, and Ethyl Ferulate offers protection against UV-induced degradation of the formula.

3. Formula Suitability for Outdoor Construction Work: Your formula appears well-suited for use during outdoor construction work under strong sun and dusty conditions. The high levels of Zinc Oxide and Titanium Dioxide provide strong broad-spectrum UV protection. The water-in-oil/silicone base with WaterGuard Lite offers water resistance, which is beneficial for outdoor activities. The inclusion of LipidSoft Lite, Dimethicone Light, SelectSorb, and Hydroxyapatite helps to create a lighter texture, control oiliness, and reduce shine, making it more comfortable to wear and reapply compared to heavier formulations. These ingredients also help the formula feel less sticky, which can prevent dust from adhering excessively to the skin. The antioxidants and anti-inflammatory ingredients like Ectoin, PolyProtect, Licochalcone A, and Carnosine can help protect the skin from environmental stressors like UV and potentially pollution/dust.

Overall, this formula is well-designed to provide high physical sun protection with a focus on a lightweight, comfortable feel suitable for reapplication in challenging outdoor conditions.