Recommended Iron Oxide Ratio for Ochre Tinted Sunscreen Cream
Question
I am formulating a tinted sunscreen cream containing ZnO and TiO2. My goal is to achieve an Ochre color similar to the Clé de Peau Beauté Crème Tinted UV in the Ochre shade.
The formulation structure involves:
- Phase A (water-based)
- Phase B (oil-based)
The pigments are dispersed in Phase B under the following conditions:
- Pigments: Iron Oxide Yellow (CI77492), Red (CI77491), Black (CI77499).
- Dispersant: Polyhydroxystearic Acid.
- Vehicle Options: Coco-Caprylate/Caprate, Cetiol CC, or Squalane.
- Process: Dispersed until smooth, then emulsified with Phase A.
- Temperature Limit: Not exceeding 75°C.
Project Specifications:
- Batch size: 1 kg
- Target pH: 6.0 - 6.5
- Must comply with Halal standards.
What are the recommended percentage ratios for the three Iron Oxides to achieve the desired Ochre shade, considering compatibility with the sunscreen base and the specified dispersion method?
Answer
The desired "Ochre" shade, similar to Clé de Peau Beauté, is a warm, medium beige with a strong yellow undertone. Achieving this requires a blend heavily weighted toward Yellow Iron Oxide.
Recommended Pigment Ratio
We recommend the following starting ratio for the three Iron Oxides, based on the total weight of the pigment blend (100%):
| Pigment | CI Number | Recommended Ratio (% of total pigment blend) | Function |
|---|---|---|---|
| Yellow Iron Oxide | CI 77492 | 85.0% | Provides the primary yellow/beige tone. |
| Red Iron Oxide | CI 77491 | 12.0% | Adds warmth and depth (red/pink undertone). |
| Black Iron Oxide | CI 77499 | 3.0% | Darkens the shade and neutralizes excessive brightness. |
| Total | 100.0% |
Note on Total Pigment Load:
For a tinted sunscreen cream, the total concentration of the Iron Oxide blend in the final 1 kg batch should typically be between 2.5% and 3.5% to provide adequate coverage and color payoff. A good starting point is 3.0% total Iron Oxide blend.
- Example Calculation for a 1 kg Batch (using 3.0% total pigment load):
- Total Pigment Weight: 1000 g * 3.0% = 30 g
- Yellow Iron Oxide: 30 g * 85.0% = 25.5 g
- Red Iron Oxide: 30 g * 12.0% = 3.6 g
- Black Iron Oxide: 30 g * 3.0% = 0.9 g
Dispersion and Halal Compliance
- Dispersion Method: Your proposed method of dispersing the pigments in the oil phase (Phase B) using Polyhydroxystearic Acid (ID 7558) is correct and highly recommended for achieving a stable, smooth, and uniform color in a sunscreen emulsion. The recommended dispersant usage is typically 10% to 20% of the total pigment weight.
- Halal Compliance: Iron Oxides are mineral pigments and are inherently Halal. Polyhydroxystearic Acid (ID 7558) and the proposed oil vehicles (Coco-Caprylate/Caprate, Cetiol CC, Squalane) are typically derived from plant sources or are synthetic, making them suitable for Halal-compliant formulations.
CRITICAL STEP: Color matching is highly subjective and depends on the specific raw materials (pigment particle size, coating, and color intensity). Always start with a small test batch and adjust the Red and Black Iron Oxides incrementally to fine-tune the shade to match the target "Ochre" color. Adding more Red increases warmth; adding more Black increases depth/darkness.
