U of S | Mailing List Archive | alt-photo-process-l | Re: BL light box 'blues'

Re: BL light box 'blues'

On Mon, 30 Mar 2009, Ken Sinclair wrote:

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.
Ken, for what it's worth I note that my time for cyanotype is circa 8 minutes...but I've got the bulbs stacked as tightly together as possible (that is, with the fixtures touching) which measures 1-1/2 inches bulb edge to edge, and the distance from the bulbs to the carrying glass (which in my setup is over, not under), is slightly less than 2 3/4 inch. I also put shiny white foam core all around the sides to reflect light *in* to avoid light fall-off around the edges, which it pretty much did.

I don't recall the developer, but those are pretty contrasty negs, printing (from memory, forgive me if I'm wrong) circa 10 steps on the 21-step.

However I recall getting an e-mail from a former student who was frantic because she was about to teach a class in cyanotype & her new set-up was clocking 25 minutes... We back-and-forthed on it for about a week, until the light dawned: It seems when she ordered the glass they asked did she want anti-glare (or some such) and she said yes, which it occurred to someone or other cut down the light.

Meanwhile and in any event... you mean you don't have a 21-step? Or access to a densitometer? Tsk tsk...!!! But if you mail me a neg (you're in the US, no?) I'll measure it for you. Sorry, I've run through my supply of 21-steps (I used to get 100 at a time for classes, & send subscribers small refunds in 21 steps), but I assume Stouffer is still in business and findable on the web... And whether you do pyrocat or hang-the-cat, trust me, the 21-step -- preferably at least 10, because you can do 10 "tests" (variables) at a time, is a crucial tool.

But, whatever you do, NOT BLB bulbs. They're at least 20% slower, and not as well formed a tone.

Meanwhile -- enjoy !


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?


Quando omni flunkus moritati (R. Green)