Design Nomenclature / Surface & Material
Iridescence
Also called goniochromism, thin-film interference, structural color
Color that shifts with viewing angle, produced by thin-film interference: light reflecting off the top and bottom faces of a film only a wavelength or so thick arrives out of phase and cancels selectively. Soap bubbles, oil on water, beetle elytra, anodized titanium. Structural — there is no pigment in it.
Not to be confused with
- PearlescenceThe soft, layered glow of many thin platelets — mica, nacre, coated flakes — suspended at varied depths beneath a translucent surface, each catching light at a slightly different plane. The angular shift is broad and low in saturation, and the depth comes from the spread of the platelets, not from any single reflection.
- LusterThe character of a surface's reflected light rather than its quantity. Mineralogy names the kinds — vitreous, metallic, waxy, resinous, greasy, silky, adamantine, dull — and they are not points on one scale. Two surfaces can meter identical gloss and read as entirely different materials, because luster folds in transparency, subsurface scattering, and structure.
- MetamerismTwo samples with different spectral curves matching under one illuminant and separating under another. The match was never in the samples — it was in the three cone responses they happened to coincide on. Hence the fabric matched under shop light that splits apart in the street, and the conditional nature of every ink-to-screen approximation.