Laboratory Protocol & Calibration Standard
CIE D65 Colorimetry & Oleic-Acid Sebum Wetting Protocol
Every CIE L*a*b* coordinate and oxidation shift reported on Make & Up is normalized to 45-degree circumferential illumination over standardized Leneta opacity charts at controlled film thickness, eliminating smartphone white-balance drift.
Make & Up measures complexion pigments using a 45/0 bidirectional spectrophotometer geometry under CIE D65 (6500K) 10-degree observer conditions. Films are cast at 25 micrometers wet thickness on neutral white/black drawdown cards, cured 15 minutes at 22C, then challenged with 5 uL synthetic triolein/squalene sebum to measure two-hour delta-E2000 darkening.
| Measurement Parameter | Standard Bench Setting | Tolerated Drift Threshold | Clinical / Visual Relevance |
|---|---|---|---|
| Primary Illuminant & Observer | CIE D65 (6504 K), 10-deg (CIE 1964) | Metamerism check at A (2856 K) and F11 | Reveals green/violet shifts under indoor warm tungsten lamps |
| Optical Measurement Geometry | 45-deg circumferential / 0-deg normal (SPIN excluded) | Repeatability delta-E <= 0.15 | Prevents dewy dimethicone highlights from reading artificially lighter |
| Wet-to-Dry Drawdown Cure | 25 um applicator blade, 15 min at 22 C / 45% RH | Volatile evaporation within +- 60 s | Separates transient carrier flash-off darkening from pigment oxidation |
| Artificial Sebum Wetting Challenge | 5 uL squalene/triolein (35:65) per 4 cm2 | Delta-E2000 < 1.2 = low shift; >= 2.2 = severe orange shift | Quantifies wetting-induced refractive-index darkening on uncoated oxides |
| Contrast Ratio Opacity Metric | Y-reflectance over black vs white Leneta panels | CR < 0.35 sheer; 0.35-0.65 medium; > 0.65 high | Measures how strongly underlying erythema shows through the film |
Primary Metrology & Regulatory Citations
CIE color difference formulas follow ISO/CIE 11664-6 (CIEDE2000) reference parameters. Cosmetic pigment purity limits reference U.S. 21 CFR Part 73 Subpart C and European Commission CosIng Annex IV.