Using Soy Lecithin as an Emulsifier in Lotion

Based on your questions about using Soy Lecithin in lotion formulations:

Water and Soy Lecithin Percentage

Soy Lecithin acts as a co-emulsifier, primarily suitable for water-in-oil (W/O) emulsions. It can be challenging to create stable oil-in-water (O/W) lotions (which are more common) with high water content using Soy Lecithin alone, as you experienced with 50% water separation.

• The typical usage rate for Soy Lecithin is 3-10%, depending on the amount of water and oil in the formula.
• For formulas with higher water content, you would generally need a higher percentage of Soy Lecithin, or more effectively, use it in combination with a primary emulsifier.
• A suggested starting point to avoid separation, as indicated by staff, is a formula with a much lower water percentage, such as 10% water, 5% Soy Lecithin, and 85% oil. If you increase the water content, you will likely need to increase the Soy Lecithin percentage significantly or add a primary emulsifier to maintain stability.

Techniques for Using Soy Lecithin

To effectively use Soy Lecithin in your lotion:

• Dissolve in Oil Phase: Always dissolve the Soy Lecithin powder in the oil phase of your formulation, typically with heating to around 80°C to ensure it fully incorporates.
• Combine Phases: Once dissolved, carefully mix the heated oil phase (containing the Lecithin) with your heated water phase.
• Use with a Primary Emulsifier: Since Soy Lecithin is a co-emulsifier and better suited for W/O emulsions, for stable O/W lotions, it is highly recommended to use it alongside a suitable primary O/W emulsifier. This will significantly improve the emulsion's stability, especially with higher water percentages, and help prevent separation.

Suitable Preservative

You can use Phenoxyethanol as a preservative in your Soy Lecithin-based lotion. It is generally compatible.

• Mixing: Phenoxyethanol is typically added during the cooling phase of your emulsion, after the main mixing is complete and the temperature is below 80°C, often as one of the final ingredients.
• Broad-Spectrum Protection: While Phenoxyethanol is effective against bacteria, it is less effective against fungi. For comprehensive protection against a wide range of microorganisms, it is advisable to either combine Phenoxyethanol with another preservative that covers fungal activity or choose a broad-spectrum preservative blend instead.

By understanding Soy Lecithin's properties as a co-emulsifier and implementing these techniques, you can improve the stability of your lotion formulations.