HID unit for pt/pd printing

[Hunter Howard]

I just read Sandy Kings article on UV light sources for pt/pd printing on the Un blinking Eye web site. This looks like a great light source for pt/pd printing. Has anyone used one? Or any comments on other UV light sources.

[Brian Ellis]

I haven't seen the article but it's pretty easy to build your own UV light unit. All you need is plywood cut to create a box of whatever size you want (about two or three inches larger all the way around than your largest contact printing frame), open at the two long sides and the bottom. The height of the box should be of a size such that when you put the florescent bulbs underneath the top, they will be about three inches above the contact printing frame you'll be using. It seems like this would result in uneven exposures but it doesn't and if you get them much higher your already long alt process exposure times become even longer. Then go to Home Depot, buy some under the counter florescent light fixtures, then at a light specialty store buy some BL (not BLB) florescent bulbs in whatever length you want. Wire the fixtures, attach them underneath the top of your box, and you're ready to go. The only slightly complicated part is wiring the fixtures (complicated for me because I know nothing about electrical work, probably not complicated at all for someone with a little more knowledge). I've seen light boxes with elaborate on/off switches and dedicated timers but that's never seemed necessary to me. Alt process times are almost always measured in minutes, not seconds, so whether you make an exposure for six minutes or six minutes and five seconds has never seemed critical to me. OTOH, I use mine for Van Dyke and gum printing, not platinum, perhaps platinum times are more critical. There's a lot of information about UV light sources in the archives of the alt.process.photo list, subscription information to which I unfortunately don't have at hand. Perhaps someone else can post it.

[Jorge Gasteazoro]

Brian, check out the article since this is entirely a different type of light. As you pointed out the light boxes are simple to make but I think the light Hunter is refering too has a different type of requirements.

[Chad Jarvis]

I use a metal halide for POP printing. While more expensive that fluorescents, you'll get faster exposure times and higher ultraviolet vs. visible light than with the former. All you need is a ballast, a fixture and a bulb.