Understanding Your Wash Formula Issues

It sounds like you're experiencing common stability problems with your wash formula, specifically cloudiness, precipitation, and a rancid smell. This often happens in water-based formulas containing ingredients like Coco Wash (PEG-7 Glyceryl Cocoate) and Polysorbate 20, which are types of esters.

Why Instability Occurs

The main culprits are usually:

• Hydrolysis: Esters can break down in water over time, especially depending on the pH. This breakdown can cause cloudiness and precipitation.
• Oxidation: The fatty acid parts of these ingredients can react with oxygen, leading to the unpleasant "rancid" smell you've noticed. Heat, light, and even trace metals can speed this up.
• Microbial Growth: While you used a preservative, if it's not the right type or concentration for your specific formula and pH, microbes can grow, causing cloudiness, precipitation, and off-odors.
• Ingredient Quality: The purity of ingredients like Polysorbate 20 can affect stability. Some impurities can act as catalysts for degradation. Consider using a higher purity grade like HiPure PS20.
• Storage: Exposure to heat, light, and air can significantly shorten the shelf life of the product.

How to Improve Stability and Shelf Life

Here are some steps you can take:

1. Adjust pH: Check and adjust the pH of your final formula. A slightly acidic pH (often between 4.5 and 5.5) is generally better for the stability of ester-based ingredients and can also help your preservative work effectively.
2. Add an Antioxidant: Include a cosmetic-grade antioxidant in your formula. This will help protect the fatty components from oxidation and prevent rancidity.
3. Review Preservation: Ensure your preservative system is robust enough for the formula's composition and pH. Consider using a broad-spectrum preservative system.
4. Consider Ingredient Purity: If possible, use high-purity grades of ingredients, such as Super-Refined Polysorbate 20, which are processed to remove impurities that can cause instability.
5. Optimize Solubilizer Level: The fact that adding more Polysorbate 20 initially cleared the product suggests the original amount wasn't sufficient for long-term stability. You may need to find the optimal level through testing.
6. Proper Storage: Always store the finished product in a cool, dark place, in a well-sealed container, away from direct sunlight and heat.

By addressing these factors, you can significantly improve the clarity, appearance, and odor stability of your wash formula over time.