Sunscreen Formulation Questions

Based on the formula you provided and the staff's reply, here are the answers to your questions:

Water Resistance

The original formula uses an oil-in-water emulsion system, as confirmed by the staff. This type of formulation is generally not waterproof. To achieve water resistance, a water-in-oil emulsion system is typically required.

Adding Kaolin

To add color and potentially help with oil absorption, you can add Kaolin (China Clay) and Beige Iron Oxides EasyMix™ as suggested. The recommended usage rate for Kaolin (China Clay) in cream formulations is typically 1-5%. You can start with a percentage within this range, such as 3%, and adjust based on your desired texture and oil absorption.

Adding Preservative and Allantoin

The Aloe Vera Gel (Heavy) base you are using already contains 0.4% Allantoin and 0.4% Phenoxyethanol (a preservative).

• Allantoin: If you add an additional 1% Allantoin, the total Allantoin concentration in the final formula would be 1.4% (0.4% from the base + 1% added). Please note that Allantoin has limited solubility in water (around 0.5% at room temperature). While heating the formula to 60°C will increase solubility, the Allantoin may precipitate as the formula cools. You might consider adding less Allantoin or using a solubility enhancer like Natural Betaine if precipitation is an issue.
• Preservative: Adding an additional 1% of a preservative on top of the 0.4% Phenoxyethanol already in the base would result in a total preservative concentration of at least 1.4%. The typical maximum recommended usage rate for Phenoxyethanol is 1%. Adding a total preservative amount above the recommended maximum for the specific preservative(s) used can potentially cause skin irritation or affect formula stability. It is important to select a preservative suitable for your formula and ensure the total concentration is safe and effective.

To incorporate the additional ingredients (e.g., 3% Kaolin, 1% additional preservative, 1% additional Allantoin), you will need to reduce the percentage of the original ingredients to keep the total formula at 100%. The most common approach is to reduce the main component, which is the Aloe Vera Gel (Heavy) base.

Here is an example of how you could adjust the formula, assuming you add 3% Kaolin, 1% additional preservative, and 1% additional Allantoin:

Original formula total: 100%
Added ingredients total: 3% (Kaolin) + 1% (Preservative) + 1% (Allantoin) = 5%
Percentage of original ingredients needed: 100% - 5% = 95%

To maintain the relative proportions of the original ingredients, multiply each original percentage by 0.95:

• Titanium Dioxide Nano EasyDisperse: 3.5% * 0.95 = 3.33%
• Silk Mica Powder: 10% * 0.95 = 9.5%
• Dimethicone Light: 17% * 0.95 = 16.15%
• Luxury Cream Maker: 0.3% * 0.95 = 0.29%
• Aloe Vera Gel (Heavy): 69.2% * 0.95 = 65.74%

Adjusted Formula Example:

1. Titanium Dioxide Nano EasyDisperse: 3.33%
2. Silk Mica Powder: 9.5%
3. Dimethicone Light: 16.15%
4. Luxury Cream Maker: 0.29%
5. Aloe Vera Gel (Heavy): 65.74%
6. Kaolin (China Clay): 3%
7. Preservative (additional): 1%
8. Allantoin (additional): 1%

Total: 3.33 + 9.5 + 16.15 + 0.29 + 65.74 + 3 + 1 + 1 = 100.01% (slight rounding difference)

Remember to adjust the percentage of Kaolin (China Clay) within the 1-5% range and recalculate the other ingredients accordingly. Also, carefully consider the total concentration and type of preservative and the solubility of Allantoin when making your final formulation.