Digital BW, The Print

Clayton Jones wrote:
> Hello Roger,
> 
>> In the Aardenburg tests, for each file (click on the free blue ones)
>> it has text at the beginning explaining light levels vs WIR years
> 
> Great chart, thanks for the link.
> 
> Speaking of Aardenburg, I received an email from someone there today
> who, after confirming the calculation of 5 WIR years, added this:
> 
> "Now, WIR uses fluorescent lamps in testing, so you've got 
> considerably higher UVB and UVa content since you are using natural
> daylight and no glass filter. That means you may have a harsher test 
> by a factor of 2-5. So your test may be roughly comparable to a 10-
> 25 years of display via WIR method. That said, the difference in
> spectra may accelerate some components more than others. Additionally,
> your samples probably got a lot hotter during the illumination cycle
> than would occur under normal indoor display, and high temperatures
> strongly desiccate prints even when they are in an otherwise humid 
> environment. Often, said desiccation will slow reactions that depend
> on water as one of the reacting species (a lot of common hydrolysis
> reactions for photographic and paper products)."

The low humidity in the samples itself caused by the 
illumination has been discussed here before.
Faster Xenon light testing could show it, even when the 
chamber is humidified the sample can have raised temperature 
and lower humidity.

For testing prints that will be used indoors at least one 
piece of glass should be used if exposed to sunlight. Normal 
window glass cuts UV out at approximately 350 Nm. If I do 
not trust a paper that hasn't been tested somewhere else I 
hang half a print in a glass window facing east. That place 
is hardly heated and humidity is usually above 50%. It 
doesn't tell me more than what I see: OBA fading, paper 
yellowing, image bleaker, but that's enough to decide for 
what kind of work it is still suited or whether it is not 
usable at all.

-- 
Met vriendelijke groeten, Ernst


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