Understanding SPF Values and Sunscreen Formulation

Thank you for sharing the interesting observation regarding SPF testing and imported vs. Thai sunscreens. It is true that differences in testing methodologies can lead to variations in reported SPF values, even for products with similar active ingredients.

Achieving a high and stable SPF value in a sunscreen formulation depends on several factors, including:

• Type of Sunscreen Filters: Different filters protect against different ranges of UV radiation (UVA, UVB). Combining filters like Octocrylene (primarily UVB, helps stabilize Avobenzone) and BEMT (broad-spectrum UVA/UVB, highly stable) is often necessary for comprehensive protection.
• Concentration of Filters: The amount of each sunscreen filter used directly impacts the level of protection. However, simply increasing the concentration isn't always the solution; the filters must be effectively dispersed or dissolved in the formula.
• Formulation Base: The base of the sunscreen (e.g., lotion, cream, spray) and the other ingredients used (like solvents such as LipidSoft SPF) play a crucial role in how the sunscreen filters are distributed and how well they perform on the skin. Ready-to-use bases like Clear Sprayable Sunscreen or Pure Physical Sunscreen (containing physical filters like Zinc Oxide and Titanium Dioxide) provide a starting point for formulations.
• Testing Method: As you noted, the specific method used to test SPF can influence the final result.

Formulating an effective sunscreen requires careful consideration of these factors to ensure both high protection and a pleasant texture.