leather

Index      Requirement        illustration
Color fastness (lightfastness)          ≥ level 7 (ISO 105-B02)      Luxury goods/automotive interiors require a level 8 rating, and new pigments like BioBlack TX can achieve 8/8.
Abrasion resistance       Dry rubbing: ≥4th grade, Wet rubbing: ≥3rd grade        If iron oxide is poorly dispersed, it is prone to fading; optimization can improve the color fastness by 1–2 grades.
Heavy metal content      Compliant with REACH and RoHS        Lead, cadmium, mercury, and hexavalent chromium must not be detectable; this is a mandatory requirement for export. 
Dispersion        Particle size: 0.4–0.7 μm, 3000 mesh or finer      Needle-shaped (yellow) or spherical (red/black), affecting the uniformity of penetration.
pH adaptability       3–8 (depending on the type of leather)     Vegetable-tanned leather is slightly acidic (pH 3–5) and requires stable iron oxide to prevent discoloration.
Tinting strength       95–105% (compared with  the standard sample)         High purity (Fe₂O₃ ≥96%) ensures color saturation.
Water-soluble salt  ≤0.3%      Excessive amounts can cause the leather to "whiten" or affect the adhesion of the coating.