If you're going to build your own UVBL lightsource, you'd better opt for "electronic" ballasts. They're more productive (higher refresh rate, less flicker, more energy output per given exposure time...) and they keep the bulbs in good shape for a longer time (thanks to complex - microprocessor controlled - start routines).
I use several different types of UV light. Self ballasted reflector mercury vapor lamps make for a nice portable system -- I use a 450W and a 750W bulb, but I don't see them in in the catalogs anymore, so they may be hard to find. This is the type I use for carbon printing. I use the "pizza oven" style of light (box of black-light tubes) for pt/pd.
The type of lamp and its strength can affect sharpness, contrast, and printing time.
There are also these single self-contained Blacklights -- plug in and expose -- but you would need perhaps 5 or 6 for an 8x10.
But there are also other flourence bulb fixutures you can buy ready to go -- just buy the blacklight tubes. There are two types -- BL and BLB. Not much difference in UV output, but the BLB has a more expensive visible light filter built in (the BL's are white like regular tubes)
I use six of those fixtures to expose up to 16x20. Contrary to popular belief, the tubes do not have to be a fraction of an inch apart to provide even coverage. I have them screwed to the bottom of a shelf in an IKEA adjustable shelving unit. The next shelf down is about six inches below the shelf with the bulbs attached, which puts my contact frame's glass about 1" - 1 1/2" from the bulbs. I typically get 6-7 minute exposures for pt/pd printing, and it looks like I'm in the sub 5 for gum bichromate.
I went to the pet store last night and they have an awesome selection of bulbs. The beauty is; they all present the UV output on the package! The Repti-Glo Desert light seemed to have the best output. I don't know and haven't yet checked how this compares to black-light bulbs or whatever, but it's something to consider.
To make the best choice, we need to know what slice of the spectrum our material is most sensitive to.
How about dichromated gelatin, what is it's peak sensitivity?
Last edited by holmburgers; 11-10-2010 at 12:52 PM. Click to view previous post history.