The optical reconstruction of the mirror phenomenon
HHDRV Ch. 19 · Compiler's note
Earlier revisions attributed the missing reflection to an anti-reflective property of the dermal metabolic oil, and to narrow-band destructive interference between that oil and the silver backing in the near-ultraviolet.
01
An anti-reflective layer on the skin governs how much light the skin returns; it does not govern whether the mirror forms an image. Baseline human skin is already an overwhelmingly diffuse reflector, and a mirror renders it perfectly well. The earlier account confused the optics of the subject with the optics of the reflector.
02
Interference in the near-ultraviolet cannot degrade an image assembled by the human eye from visible wavelengths, and the soda-lime glass of every mirror under discussion is in any case substantially opaque below approximately 350 nanometres.
03
Thin-film interference of the kind invoked requires an optically uniform layer of controlled thickness and a coherent source, and no sebaceous secretion spread across the topography of a human face satisfies either requirement.
Two stacked conditions. Cumulative silver-sulphide foxing on unsealed silver-backed mirrors — conservation literature, not a claim of the organism — and a refractive gradient in the cold boundary layer, light twice at thirty to sixty centimetres. Aluminium vapour-deposition from the 1930s forms no sulphide and self-passivates. The present account is offered at a lower confidence grade than the galvanic mechanism that precedes it in the same chapter. Falsification is Path Four-A. The compiler withdraws the earlier mechanism without reservation.