Re: outdoor gum demo

[Alberto Novo <alt.list@albertonovo.it>]

> it's very interesting that greenish brown/brownish green/brownish stain
> color is pretty effective at blocking UV (visible light DR and UV DR is
> different) for pyro-developed silver/gelatin negatives, whereas
> "coincidentally" green color is the strongest UV blocker for many inksets
> / printers. Two most different medias (printer ink / stained gelatin)
> exhibiting similarities in the same context -> confusing indeed.
IF the UV absorption is extended in the visible range,
THEN
there is some absorption *also* of the blue radiation, so that chiefly 
yellow is transmitted (brown is a dark yellow).
BUT (not a logical variable :-)  )
this is not a universal rule (again, think to sun oils...) 
> Not that I'm interested in pursuing -> just mentioned for the records...
:^) 
Alberto