Tarnished Silver — Sulphide Patina Interference Layers
339.00 د.إ
Sterling silver in the process of tarnishing — the silver sulphide (Ag₂S) film at intermediate thickness showing the interference colour sequence from gold through magenta to blue as the film grows from zero to 200nm.
Description
Silver tarnish is a thin-film interference phenomenon identical to oil-slick colours — as the silver sulphide layer grows from zero to 200nm, the interference between light reflected from the Ag₂S surface and light reflected from the Ag-Ag₂S interface produces colour sequences that advance through the standard thin-film colour sequence. This image captures a silver object at the intermediate tarnish stage — typically 48 to 72 hours of atmospheric exposure in a sulphurcontaining environment — where the sulphide film thickness varies across the surface from approximately 50nm at the least-exposed regions to 200nm at the most-exposed, producing a complete colour gradient from the gold colour of the thinnest film through orange, red, magenta, violet, and blue at the thickest. Shot at 1.5:1 macro with raking sidelight, the colour variations are sharply defined at the boundaries between regions of different film thickness.
