With the demise of Kodak papers, I've taken up alternative printing. I tried Cyanotype at a friend's, but don't care for the blue color. I ordered a Vandyke brown kit from Photographer's Formulary.
First step after mixing the chemicals was to find a suitable bulb for exposure. I have a device made from PVC that holds a bulb and reflector about 18" above my printing frame, so I decided to try some bulbs I had around the house. I first tried a 15-watt BLB florescent bulb. After an hour and a half of exposure, I gave up. It was still insufficient. I next tried a 65-watt GE Reveal bulb. This bulb is sold as one with a lot of blue light, and the bulb itself is certainly a purple color. It was also unacceptable, however, as a printing bulb. After an hour of printing, it still produced a print that was underexposed.
I next tried a 100-watt R-40 halogen bulb. I turned it on with my timer and turned to clean up something in the darkroom. When I looked back at the printing frame about 30-seconds later, I could see the paper under the clear film edges turning brown. It appears that proper exposures will be somewhere in the 5-10 minute range with this bulb, which makes is acceptable to me.
Other folks build huge arrays of UV florescent bulbs that cost in the $100 range. Others have found UV light sources discarded by printers. It appears with these first tests that the 100-watt halogen bulb works just as well as the more expensive UV arrays at a cost of only a few minutes time. The bulb itself costs less than $10.