[quote="fhovie"]I read a lot of fine articals -" Thanks all. I am considering using a bank of Black Light bulbs and I have the following questions: Do they have to be florecent? - there are a lot of 75W black light incandecent bulbs available cheap?"

Frank,

I don't know if the BL incandescent bulbs put out enough UV light. But if they are really inexpensive I would buy one and stick it in a 10" reflector and try to expose a 5X7 or 8X10 cyanotype at a distance of about 15" from the light to the printing frame. If you get enough density with an exposure of less than 20 minutes it would probably be feasible to gang up 4-6 of these lights to get enough illumination for prints up to 11X14 or 16X20 size.

One inexpensive light that does put out a lot of UV radiation is the common 175 watt mercury vapor lamp available in night lights. If you use this unit at about 10" from the printing frame you will get reasonably short exposures and be able to print up to about 8X10" size without excessive light fall-off at the edges. You will need to tape off the senor on the top of the light. Just hang it the ceiling or bolt it to the wall and you are in business. Leave it on for the duration of the printing session because the light takes about 5-7 minutes to reach maximum output. At a cost about $40, including ballast, reflector and bulb this is about the least expensive UV source available.