Digital BW, The Print

Tom Baker wrote:
> Paul wrote:   "...It surprises me that even under UV glass the spray would add that much."
>  
> At least the high end uv glasses claim 99+% uv blockage.  So, how could the expected life of the print be doubled by spraying?  Something doesn't seem to add up here.
>  
> Tom Baker

Visible light contributes much more to fading in this test 
than UV. So UV is just one of the fading dangers. There's also 
gas fading, humidity etc that can be blocked by a thicker 
layer of (UV) varnish. The ozone test result may give the 
explanation.  That a (thicker) varnish will influence the 
print's appearence before the test starts is without doubt. So 
will another paper color. Wilhelm only measures the 
differences between a good print and the print in test till 
the last gets an unacceptable shift to the original.

Ernst