Understanding the Issues

Emulsion Separation

Your lotion is an emulsion, which means oil and water phases are held together by emulsifiers (Glyceryl Monostearate and Tween 60/Polysorbate 60). Separation occurs when this emulsion breaks, and the oil and water layers split. Common reasons for this include:

• Insufficient or Imbalanced Emulsifiers: While you have both Glyceryl Monostearate and Tween 60, the ratio and total amount relative to your oil phase might not be optimal for long-term stability. Glyceryl Monostearate (especially the SE type) helps, but a proper balance with Polysorbate 60 is key.
• Incorrect Heating Temperature: Both the oil phase (containing Stearic Acid, Fractionated Coconut Oil, Shea Butter, Lanolin, Glyceryl Monostearate, Tween 60, and extract) and the water phase (Water, Glycerin, Preservative - check preservative heat tolerance) must be heated to a sufficient and similar temperature (typically 70-80°C) to ensure all solid/semi-solid ingredients are melted and the phases can combine properly.
• Insufficient Mixing During Emulsification: The initial mixing when combining the heated oil and water phases requires adequate shear to create small, stable oil droplets dispersed in the water phase.

Air Bubbles

The air bubbles are almost certainly caused by the high mixing speed you are using. 5000 rpm is very high for a lotion and will whip a significant amount of air into the product, especially if mixed at that speed for 5 minutes.

Recommendations for Improvement

To address the separation and air bubbles, try adjusting your process:

1. Heat Phases Properly: Heat your oil phase ingredients (Stearic Acid, Fractionated Coconut Oil, Shea Butter, Lanolin, Glyceryl Monostearate, Tween 60, Extract) and your water phase ingredients (Water, Glycerin, Preservative - check preservative heat tolerance) separately to around 75-80°C. Ensure everything in the oil phase is fully melted and clear.
2. Combine and Emulsify: Add the heated water phase to the heated oil phase (or vice versa, consistently) while mixing. Use a moderate mixing speed (lower than 5000 rpm, perhaps 1000-2000 rpm depending on your mixer) during this combining step and for the first 5-10 minutes to properly form the emulsion.
3. Cool with Slow Mixing: After the initial emulsification period, switch to a very slow mixing speed (e.g., 100-300 rpm). Continue mixing at this slow speed while the lotion cools down to below 40°C. Slow mixing during cooling helps stabilize the emulsion and allows trapped air bubbles to escape. Avoid high-speed mixing during the cooling phase.
4. Add Heat-Sensitive Ingredients: If your preservative or extract are heat-sensitive, add them during the cooling phase, typically below 40°C, while mixing slowly.
5. Allow to Rest: Once the lotion has cooled and thickened, transfer it to its final container and let it sit undisturbed for 24-48 hours. This resting period allows any remaining small air bubbles to rise and dissipate, resulting in a smoother texture.

By ensuring proper heating, using appropriate mixing speeds during different stages, and allowing the product to rest, you should be able to achieve a more stable, homogenous lotion with fewer air bubbles.