Color and Appearance Metrology in Vat-Printed Photopolymers: CIELAB, CIEDE2000, Metamerism, Gloss, Surface Texture and Gonioappearance

Color and appearance in vat photopolymerisation are coupled material-process-surface properties. CIELAB coordinates describe a color stimulus under declared measurement conditions, while CIEDE2000 provides a defined color-difference calculation from CIELAB coordinates. Neither quantity is independent of illuminant, observer, measurement geometry, background or specimen state. Additive-manufacturing studies show that printing orientation, layer thickness, post-curing, polishing, glazing, ageing media and surface roughness can alter measured color and translucency. Independent work on 3D-printed polymers also demonstrates that gloss and roughness change with surface finishing, making visual match a broader problem than chromatic coordinates alone. This Engineering Review defines minimum controls for color matching, batch comparison, post-process drift and appearance qualification in vat-printed photopolymers. It distinguishes ordinary diffuse/opaque specimens from translucent, fluorescent and gonioapparent metallic systems, for which single-geometry color data can be incomplete. 3Dresyns Custom RAL/NCS Colours, Basic Color Pastes, Special Metallic Colors and 3D-ADD MATT1 are included only as manufacturer implementation examples; no universal ΔE tolerance, gloss target or cross-printer color equivalence is inferred from product positioning.