Using Soy Lecithin and other Emulsifiers in Cream and Sunscreen Formulas

Subject: Regarding Soy Lecithin and Cream Formulas

Hello,

Thank you for your questions regarding your cream formulas and Soy Lecithin. I will address each of your points based on the information provided.

1. Regarding your first formula (Water 71%, Safe-B3 8%, Panthenol 3%, Soy Lecithin 10%, Yeast Radiance 3%, Silicone Quick-Cond 2%, GlucoBright 4%, Phenoxyethanol SA 1%): This formula primarily contains water-soluble ingredients and a high percentage of water (71%). As the staff mentioned, Soy Lecithin is an emulsifier that works best in formulas with a very high oil content (typically 70-80% oil). In a formula with such high water content, Soy Lecithin alone cannot create a stable cream or lotion texture. It would likely result in a liquid or separated mixture. To create a gel texture with these water-soluble ingredients, you would need to use a water-phase thickener/gel former like Pro Polymer or AnyGel, and omit the Soy Lecithin if you are not including an oil phase.

2. Does Soy Lecithin need to be dissolved only in oil? Soy Lecithin is oil-soluble and functions as an emulsifier for oil-in-water or water-in-oil emulsions, particularly effective in formulas with a high oil phase (70-80%). While it dissolves in oil, the staff mentioned it can sometimes be added at the final step and blended in, but its primary function as an emulsifier relies on being incorporated into the oil phase when creating an emulsion with a significant oil component. For high-water formulas, it is not the appropriate emulsifier.

3. If adding fragrance, is an additional emulsifier needed? Yes, adding fragrance (which is typically oil-based) to a water-based or emulsion formula often requires an ingredient to help disperse and incorporate it evenly. Emulsifiers or thickeners/gel formers like Pro Polymer, AnyGel, or Milk Lotion Maker can help stabilize and incorporate fragrance into the formula. The staff also recommended using fragrance oils specifically designed for skin products rather than flavor oils.

4. If replacing Soy Lecithin with Shea Butter in the first formula, would it work? Shea Butter is an emollient (a type of oil/fat) that provides moisturizing properties and contributes to the texture of a cream, but it is not an emulsifier. It cannot replace Soy Lecithin's function of binding oil and water together. To use Shea Butter in a cream, you would need to include it in the oil phase and use an appropriate emulsifier (like Milk Lotion Maker) to create a stable emulsion with the water phase. Shea Butter also requires heating to melt before mixing.

5. Can water-soluble and heat-tolerant ingredients be added after mixing the oil phase and cooling? For the first formula you provided, the staff indicated that no heat is necessary as all ingredients dissolve at room temperature. However, as a general principle in cosmetic formulation, heat-sensitive ingredients (whether water or oil soluble) should be added after the main emulsion has formed and cooled down to a suitable temperature (usually below 40-50°C) to preserve their efficacy. Ingredients that are water-soluble and heat-tolerant could be added to the water phase before mixing or after cooling, depending on the specific process and desired outcome.

6. Is measuring pH the final step, and adjusting if necessary? For the specific ingredients in your first formula, the staff stated that pH measurement and adjustment are not necessary because the ingredients are generally mild and result in a skin-friendly pH. However, in general cosmetic formulation, pH adjustment is often a final or near-final step, especially when using ingredients that are pH-sensitive or when a specific pH range is required for efficacy, stability, or skin compatibility. You would measure the pH and then adjust it up or down using appropriate acidic or alkaline solutions if needed.

Regarding your second formula (Water 68%, Soy Lecithin 9%, Shea butter ultra soft 5%, Safe-B3 8%, Yeast Radiance 3%, GlucoBright 4%, Phenoxyethanol SA 1%, Silicone Quick-Cond 2%) and mixing steps:

As the staff explained, this formula still has a high water content (68%) relative to the oil phase (Shea Butter 5% + Silicone Quick-Cond 2% = 7%). Soy Lecithin at 9% is intended for formulas with a much higher oil phase (70-80%). Therefore, Soy Lecithin is not suitable as the primary emulsifier here, and this formula will likely not form a stable cream using Soy Lecithin alone.

The staff recommended using Milk Lotion Maker (3%) along with Pro Polymer (0.5-1.0% for thickening) instead of Soy Lecithin for this formula to create a stable cream texture.

Your proposed mixing steps (A: Soy Lecithin + Shea Butter at 80C, B: Water + others, then B+A) are incorrect for this formula and the recommended emulsifiers. If using Milk Lotion Maker and Pro Polymer as recommended by staff, the process would involve heating the oil phase (Shea Butter, Milk Lotion Maker, Silicone Quick-Cond) and water phase separately, then combining them while blending, and adding heat-sensitive ingredients and Pro Polymer (which is often added to the water phase or after emulsion formation depending on type) during or after cooling.

Regarding your follow-up questions:

• Is Pro Polymer a chemical? Yes, Pro Polymer (Acrylate Crosspolymer) is a synthetic polymer used as a thickener and stabilizer in cosmetics.
• Can Xanthan Gum replace Pro Polymer if avoiding chemicals? Xanthan Gum is a natural gum used as a thickener, but it is not an emulsifier and cannot effectively bind oil and water like Soy Lecithin or Milk Lotion Maker. It can thicken the water phase but won't create a stable emulsion if you have an oil phase.
• How to use Soy Lecithin since you already purchased it? Soy Lecithin is best used in formulas where the oil phase constitutes the majority (70-80%) of the formula, such as rich creams, balms, or oil-based lotions. You would need to formulate a recipe with a significantly higher oil percentage than your current attempts for Soy Lecithin to function correctly as the primary emulsifier. The staff mentioned it could be added at the final step and blended in for suitable formulas.
• Can Soy Lecithin be used in a sunscreen formula? As stated earlier, Soy Lecithin requires a very high oil phase (70-80%) to emulsify effectively. Sunscreen formulas often contain a significant water phase, especially if they are lotions or creams. Therefore, Soy Lecithin is generally not suitable as the primary emulsifier for typical cream/lotion sunscreens with high water content. For the sunscreen formula you provided (Water 62%, Zinc Oxide Liquid 10%, Titanium Dioxide Liquid 20%, Milk Lotion Maker 3%, LipidSoft 3%, Strawberry Flavor 2%), the staff recommended Milk Lotion Maker (3%) + Pro Polymer (0.5-1.0%) for emulsification and thickening, which is appropriate for a formula with a substantial water phase and dispersed physical sunscreens.
• Can the sunscreen formula be mixed manually? The mixing steps provided by the staff for the sunscreen formula involve heating and blending the oil and water phases, then adding the water phase to the oil phase while blending strongly, and continuing to blend during cooling. This process, especially with physical sunscreens (Zinc Oxide, Titanium Dioxide) and emulsifiers requiring heat, typically requires mechanical mixing (like a homogenizer or high-shear mixer) to ensure proper dispersion of the powders and stable emulsion formation. Manual mixing is unlikely to achieve a stable, smooth, and effective sunscreen emulsion.

In summary, your initial formulas were not suitable for Soy Lecithin due to their high water content. Soy Lecithin is best for high-oil formulations. For your proposed cream and sunscreen formulas with significant water phases, emulsifiers like Milk Lotion Maker, often combined with thickeners like Pro Polymer, are more appropriate. Mixing processes involving oil and water phases, especially with physical sunscreens, usually require heating and mechanical blending.

I hope this clarifies your questions!