Developing a Light O/W Lotion and Calculating Emulsifier Dosage

Question

I am developing an O/W Emulsion lotion formula designed to have a light texture and fast absorption. I would like to know if the following formula is appropriate and how to calculate the correct amount of emulsifier.

Phase A

DI Water — q.s. to 100%
EDTA — 0.10%
Aloe vera Extract — 2.00%
Collagen — 1.00%
Hyaluronic Acid — 0.20%

Phase B

Sweet Almond Oil — 4.00%
Isopropyl Myristate — 2.00%
Hydrogenated Polydecene — 2.00%

Phase C

Sodium Polyacryloyldimethyl Taurate — 0.80%
Trideceth-10 — 0.40%

Phase D

Niacinamide — 3.00%
Alpha-Arbutin — 1.50%
Kojic Acid — 0.50%
Lactobionic Acid — 2.00%
mixberry Fruit Extract — 1.00%

Phase E

Phenoxyethanol — 0.80%
Fragrance — 0.20%

MySkinRecipes Expert · Accepted Answer

The lotion formula you provided is well-structured for a light, fast-absorbing texture. Below is an evaluation and recommendations for improvement:

1. Texture and Absorption

Oil Phase (8%): This is a good range for a "light" lotion. The combination of Sweet Almond Oil (natural emollient), Isopropyl Myristate (fast-spreading agent), and Hydrogenated Polydecene (smooth, non-greasy feel) will provide a very pleasant, non-tacky finish.
Polymer Base: The use of Sodium Polyacryloyldimethyl Taurate (often found in Viscolam AT 100P) creates a "water-break" effect, making the lotion feel fresh and watery upon application.

2. Emulsifier Calculation (Phase C)

The ingredients in Phase C suggest you are using a polymer-based emulsifier.

Dosage: Your current total for Phase C is 1.2%. For an oil phase of 8% and a high load of active ingredients (Phase D), this might be slightly low for long-term stability.
Recommendation: It is recommended to use a ready-to-use polymer emulsifier like Viscolam AT 100P at 1.5% - 2.0%. This will ensure the emulsion remains stable even with the electrolytes from the extracts and acids.

3. Stability and Active Ingredients (Phase D)

Kojic Acid Stability: Kojic Acid is highly unstable and oxidizes (turns brown) easily when dissolved in water. To prevent this, you should add an antioxidant stabilizer such as ActiveProtec™ OX at 1.0% in the formula.
pH Management:
- Lactobionic Acid (a PHA) will lower the pH of the formula.
- Niacinamide requires a pH of approximately 5.0–6.0. If the pH drops below 5.0, Niacinamide can convert to nicotinic acid, which may cause skin flushing (redness).
- Recommendation: Measure the final pH and adjust it to 5.0–5.5 using a pH adjuster (like Triethanolamine) if necessary.

4. Suggested Mixing Process

Phase A: Mix DI Water, EDTA, and Hyaluronic Acid until clear. Then add other Phase A ingredients.
Phase B: Mix the oils together.
Emulsification: Add Phase C into the water phase (Phase A) and stir until a gel forms, then slowly add Phase B while stirring/homogenizing.
Phase D & E: Once the emulsion is smooth, add Phase D (actives) and Phase E (preservative/fragrance). Ensure the actives are fully dissolved before adding.

Recommended Products

Viscolam AT 100P: An easy-to-use polymer emulsifier for cold or hot processes.
Hydrogenated Polydecene (Light, 6cSt): For a smooth, mineral-oil-like feel without the greasiness.
Lactobionic Acid: For gentle exfoliation and hydration.
Kojic Acid: For brightening.
ActiveProtec™ OX: Essential for stabilizing Kojic Acid against oxidation.