Re: BL light box 'blues'

[Robert Newcomb <newcombr@uga.edu>]

I'm no expert, but you might consider moving the light closer to the printing frame. The inverse square law would indicate that if you half the distance you'd pick up two stops worth of exposure speed - I think.
And, is a BL lamp the correct one - should it be BLB?
Robert N.

---- Original message ----
>Date: Mon, 30 Mar 2009 14:48:59 -0600
>From: Ken Sinclair <photo1@telusplanet.net>  
>Subject: BL light box 'blues'  
>To: alt-photo-process-l@usask.ca
>
>Have recently decided to intensify my interest in non-silver, I  
>constructed my
>new UV light-box using 10 BL tubes presently 5 inches above my  
>printing frame.
>
>So that I could use the same negatives for both silver-gelatin,  
>Cyanos and VDB
>I switched to Pyrocat as a developer... and I must admit, they do  
>look "sweet".
>
>A few years ago my southern Alberta summer sunlight exposures for  
>Cyanos were
>running around the eight minute mark... which expanded to around two  
>and a half
>hours in the rather weak December sun.
>
>The exposure times I expected using the new 24" BL tubes are nowhere  
>as short as I had
>hoped...  Cyanotypes seem to be requiring around 40 to 50 minutes  
>while I have not
>yet reached the 'end-point' for acceptable VDB exposures, it seems as  
>if 60 -70 minutes
>might be the absolute minimum.
>
>I do not have a stouffer wedge to assist reaching my standard  
>exposure times, my patience is
>wearing (as my frustration level rises).
>
>I have just put a VDB out on the deck to enjoy some natural UV rays  
>from the sun
>for a time comparison...
>
>Are my BL light-box test exposure times "out of line" with times  
>experienced by others?
>
>Ken
>
>Quando omni flunkus moritati (R. Green)
>