Cream Formulation Issue with Soy Lecithin and Preservative

You've created a natural cream formulation using Soy Lecithin as an emulsifier, along with Beeswax and Stearic Acid. It's great that the oil, water, and wax phases emulsified well initially.

The separation you observed after adding the preservative blend (Benzyl Alcohol, Potassium Sorbate, Sodium Benzoate, Water) is likely due to incompatibility between the preservative system and your emulsion.

Here's a breakdown:

• Soy Lecithin as an Emulsifier: Soy Lecithin is primarily a water-in-oil (W/O) emulsifier (HLB around 4). While it can be used in oil-in-water (O/W) emulsions (which a cream typically is, especially with 73% water), it often requires careful formulation and potentially co-emulsifiers or thickeners to achieve stability, especially at higher water percentages. Your formula includes Beeswax and Stearic Acid, which act as co-emulsifiers and thickeners, but the combination with Soy Lecithin might still be challenging for stability.
• Preservative Incompatibility: The preservative blend contains salts (Potassium Sorbate and Sodium Benzoate). Salts can sometimes destabilize or break emulsions, particularly natural emulsions or those formed with low HLB emulsifiers like Soy Lecithin. The effectiveness of Potassium Sorbate and Sodium Benzoate is also highly dependent on the pH of the formulation; they work best at lower pH values (typically below 6). If your cream's pH is too high, it could contribute to both instability and reduced preservative efficacy.

Recommendations:

1. Check the pH: Measure the pH of your final cream. If it's above 6, it could be contributing to the separation and the preservative won't be optimally effective. However, even at a suitable pH for the preservative, the salts might still be problematic for this specific emulsion system.

2. Consider an Alternative Preservative: The preservative blend you used is a likely culprit for the separation. Consider using a different broad-spectrum preservative that is more compatible with natural emulsifiers and less prone to causing emulsion breakdown.

   Based on available options, you could consider:

   • Coco-Preserve™: This is a natural preservative derived from coconut extract, water-soluble, and effective in a pH range of 4-8. It might be more compatible with your natural formulation.
   • Preserve-Free CE85™: This is a multifunctional blend that offers broad-spectrum antimicrobial activity and is stable at neutral pH. It is designed to replace traditional preservatives and is often compatible with various formulations.
   • NaturePreserve™ LB2: This is another natural origin preservative effective against bacteria and fungi, but it works best at lower pH values (2.0-6.5). You would need to ensure your cream's pH is within this range.

3. Formula Suitability: While your formula attempts a natural approach with Soy Lecithin, achieving a stable O/W cream with Soy Lecithin alone or with simple co-emulsifiers like Beeswax and Stearic Acid at 73% water can be difficult. The separation upon adding the preservative highlights this instability. Adjusting the preservative is the most direct step to address the current issue.

In summary, the separation is most likely caused by the interaction between the salt-based preservative components and your Soy Lecithin emulsion. Switching to a more compatible preservative is recommended.