Formula Review and Answers

Here is a review of your proposed sunscreen formula and answers to your questions:

Your formula aims for an SPF 30 sunscreen spray for sensitive skin, intended for reapplication throughout the day. It primarily uses Zinc Oxide as the UV filter.

Formula Components:

• Zinc Oxide 200nm EasyDisperse™ (12%): This is your main physical sunscreen filter. 12% Zinc Oxide can potentially achieve SPF 30, provided it is well dispersed in the formula. The EasyDisperse™ type is designed for better dispersion.
• Glycerin (10%) & Butylene Glycol (3%): These are humectants that help retain moisture. 10% Glycerin is quite a high percentage for a light spray intended for reapplication and might feel slightly sticky.
• Chamomile Water (Anthemis Nobilis) (10%): This is included for its soothing properties. Note that this ingredient already contains Phenoxyethanol 0.8% as a preservative.
• Butyl Octyl Salicylate (10%): This acts as an SPF booster, helping to enhance the effectiveness of the Zinc Oxide and improve the overall SPF value.
• Kaolin (5%): This is an absorbent powder that can help reduce shine and greasiness, contributing to a more matte finish.
• Light Lotion Maker (2%) & Xanthan Gum (0.20%): These are your emulsifier and thickener/stabilizer system. Light Lotion Maker is suitable for light textures and sprays, especially when combined with a small amount of Xanthan Gum to prevent separation.
• Mild Preserved Eco™ (Preservative-Free) (1%): This is a preservative blend. 1% is within the recommended usage rate for general cosmetics. It is considered gentle and allows for a "preservative-free" claim, although the Chamomile Water adds Phenoxyethanol.
• Tocopheryl Acetate (0.01%): Vitamin E, likely included as an antioxidant to help protect the oils in the formula from degradation.

Answers to Your Questions:

1. Is it suitable as a spray for sensitive skin?

   • For Sensitive Skin: The ingredients like Zinc Oxide, Chamomile Water, Butylene Glycol, and Mild Preserved Eco™ are generally considered suitable for sensitive skin. Individual reactions can vary, but the component choices lean towards gentleness.
   • As a Spray: The combination of Light Lotion Maker and Xanthan Gum is suggested for spray formulations. However, 2% Light Lotion Maker might be on the lower side to effectively emulsify and stabilize the total oil/solid phase (12% Zinc Oxide + 10% Butyl Octyl Salicylate). This could potentially lead to stability issues or difficulty achieving a fine, even spray. You might need to increase the Light Lotion Maker percentage or adjust the ratio with Xanthan Gum for better sprayability and stability.

2. Are the proportions of sunscreen, solvent, and emulsifier good?

   • Sunscreen (Zinc Oxide 12%): This concentration is potentially sufficient for SPF 30, but performance heavily relies on dispersion and the final formulation.
   • Solvents (Glycerin 10%, Butylene Glycol 3%, Water): 10% Glycerin is quite high for a light reapplication spray and may result in a slightly sticky feel. The total water phase is high, which helps with lightness, but puts more demand on the emulsifier system.
   • Emulsifier (Light Lotion Maker 2%, Xanthan Gum 0.2%): As mentioned, 2% Light Lotion Maker might be insufficient for the oil/solid load, potentially affecting stability and spray performance. Adjusting the emulsifier system might be necessary.

3. Is Butyl Octyl Salicylate necessary if only for reapplication?

   • Butyl Octyl Salicylate acts as an SPF booster. While Zinc Oxide provides broad-spectrum protection, this ingredient helps achieve and maintain the target SPF 30 more effectively with the chosen concentration of Zinc Oxide. Removing it would likely reduce the overall SPF unless you significantly increase the Zinc Oxide, which could impact the texture (whiteness, thickness). If maintaining SPF 30 is the goal for reapplication, keeping Butyl Octyl Salicylate is beneficial.

4. Can Chamomile Water mask the sunscreen smell?

   • Chamomile Water has a pleasant natural aroma from its essential oil and can help mask mild base odors. However, its ability to completely cover any strong or unpleasant smells from other ingredients (like raw material odors from Zinc Oxide or the base) depends on the intensity of those smells and the concentration of the Chamomile Water. It will likely contribute a pleasant note but may not fully mask strong odors.

5. Can Kaolin help prevent greasiness, or can it be removed?

   • Yes, Kaolin is an absorbent powder commonly used to reduce oiliness and shine. At 5%, it should help absorb excess moisture and oil, contributing to a less greasy feel and a more matte appearance, which is beneficial for a reapplication product. You can remove it, but expect the formula to feel potentially greasier or shinier without its oil-absorbing properties.

In summary, the formula has a good foundation for sensitive skin using Zinc Oxide. Consider adjusting the emulsifier concentration for better spray stability and potentially reducing Glycerin for a lighter feel suitable for reapplication. Kaolin is helpful for managing greasiness.