Lotion Formulation Issue: Phase Separation

Question

I need a lotion that is quite liquid, non-sticky, focusing on moisturizing and skin softening.

I used the following formula:

Oil Phase (heated):
1. Milk Lotion Maker 5%
2. Mineral Oil 5%
3. Cyclomethicone 3%
4. Aloe Vera Oil 2%
5. Vitamin E Acetate 2%
  
  (Mixed in the oil phase and heated)
Water Phase (heated to approximately 50°C):
1. Glycerin 2%
2. Collagen (food grade, dissolved in water)
3. Fragrance 0.25%
4. Water qs to 100%
  
  (Mixed in the water phase and heated to approximately 50°C)

Process: Poured the water phase into the oil phase.

Result: The lotion separated.

Is there a way to fix this?

Additional information: The pH of the water phase before adding collagen was about 5.6, but after mixing in the collagen, the pH measured about 6.9. I also need the product to be pH balanced.

MySkinRecipes Expert · Accepted Answer

Subject: Adjusting a Separating Layered Lotion Formula

Hello,

Regarding the lotion formula that is separating, this issue often arises from the emulsification process or ingredient compatibility. Based on your formula and method, here are some suggestions to try:

Emulsification Method: Instead of pouring the water phase into the oil phase, try pouring the oil phase slowly into the water phase while mixing continuously and vigorously. Use a whisk or a stick blender for better shear.
Mixing During Cooling: Continue mixing the lotion intermittently or continuously as it cools down. This helps stabilize the emulsion.
Cyclomethicone Addition: Cyclomethicone is volatile and can sometimes interfere with hot emulsions. Try adding the Cyclomethicone after the main emulsion has formed and cooled down to below 40°C.
Fragrance Addition: Add the fragrance at the same time as Cyclomethicone, when the lotion is below 40°C.
Collagen and pH: Food-grade collagen can sometimes affect the pH significantly. The pH of 6.9 is quite high for skin products and might contribute to instability.
- Prepare the water phase with Glycerin and water.
- Dissolve the collagen separately in a small amount of water and check its pH. If it's high, the collagen is likely the cause.
- Proceed with emulsification (pouring oil into water phase).
- Once the lotion has cooled down and you've added Cyclomethicone and fragrance, adjust the pH using a suitable acidic solution (like a dilute citric acid solution) until it reaches a skin-friendly range (pH 4.5-5.5). Add the pH adjuster drop by drop while checking the pH.
Consider Emulsifier Percentage: While 5% Milk Lotion Maker is often sufficient, if separation persists after adjusting the process, you could try slightly increasing the Milk Lotion Maker percentage (e.g., to 6-7%) to see if it improves stability, especially with the combination of oils used.

Revised Process Suggestion:

Oil Phase: Combine Milk Lotion Maker, Mineral Oil, Aloe Vera Oil, Vitamin E Acetate. Heat.
Water Phase: Combine Water, Glycerin, and dissolved Collagen. Heat to around 50°C.
Emulsification: Slowly pour the heated Oil Phase into the heated Water Phase while mixing vigorously (e.g., with a stick blender).
Cooling: Continue mixing intermittently or continuously as the lotion cools.
Add Sensitives: When the temperature is below 40°C, add Cyclomethicone and Fragrance. Mix well.
pH Adjustment: Check the pH and adjust it to 4.5-5.5 using a dilute acid solution (like citric acid).

By adjusting the emulsification technique, adding sensitive ingredients at a lower temperature, and controlling the final pH, you should be able to achieve a stable, non-separating lotion.