Re: outdoor gum demo
IF the UV absorption is extended in the visible range,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.
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...