Adding Sunscreen Ingredients to Lotion Base and SPF Calculation
Question
I want to add the following sunscreen ingredients to a body lotion base:
- Zinc Oxide 200nm EasyDisperse™ at 25%
- Avobenzone at 5%
My goal is to achieve SPF 50. Is it possible to simply mix these ingredients into an existing lotion base at these percentages to get SPF 50? What are the considerations for mixing and emulsifiers?
Answer
Based on the information provided:
You can mix Zinc Oxide 200nm EasyDisperse™ and Avobenzone into a body lotion base.
Regarding mixing:
- For Avobenzone (a chemical sunscreen), heat is required to ensure it dissolves completely and integrates properly into the lotion base for effective UV protection.
- For Zinc Oxide (a physical sunscreen), heat may not be necessary, but thorough mixing (e.g., using a blender) is essential to disperse the powder evenly throughout the formula for full effectiveness.
Regarding emulsifiers:
- Your base lotion already contains emulsifiers.
- If you add a small amount of these ingredients, the existing emulsifiers should be sufficient to help integrate them.
- Adding a large amount might require adjusting the formula or adding more emulsifiers, which is more complex. It is recommended to add only a small amount.
Regarding SPF 50:
Simply adding these ingredients at the mentioned percentages (25% Zinc Oxide, 5% Avobenzone) to an existing lotion base does not guarantee that the final product will have an SPF of 50. Achieving a specific SPF level requires careful formulation and testing of the final product. It is not possible to confirm the resulting SPF without proper testing.
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