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Paul204 · June 18th, 2007

i've been scouring this forum and the rest of the internet now, finding information regarding building your own metal halide exposure unit. i feel like i know what i need to do, although i still have a couple of questions.

there are different kinds of metal halide ballasts that will output light of a different frequency (or spectra, or whatever) than is needed for exposing photoemulsion. the ballasts and bulbs i'm finding are mostly on hydroponic sites.

how can i tell if this ballast and this bulb will be appropriate for screen making?
1000 Watt Metal Halide Ballast Wired RTU - Metal Halide & High Pressure Sodium Ballasts
1000 watt Sylvannia MH Clear - Metal Halide Bulbs

on an electrical note... normally, i would need a fixture that would connect the ballast to the light, wouldn't i? this website seems to not sell them, and their full light packages include only a ballast, a light and a reflector. can i use a standard fixture?

my last question regarding exposure units relates to the inside of the unit. on the sidewalls, will i want to have a sheet metal or something reflective to get the light to the glass or will i want something dark to dampen the light to make sure the light is only reaching the screen in a direct line?

any help you can offer is appreciated, sorry if you're tired of reading posts by cheap kids who don't know what they are doing...

BelovedUS · June 19th, 2007

I don't know if this helps any but, I was going to use a metal halide lighting system but I didn't. I went to Lowes and Home Depot to look for the metal halides and found a couple. Like you said, you DO need to get a fixture but, all I could find were huge outdoor light fixtures.

Quote:


	can i use a standard fixture?

No. There was standard size and oversized bulbs for metal halides. The standard sizes were 175W and I actually bought two of those, thinking they would work in a regular incandescent outlet - I was wrong, they didn't. The bulbs that I bought said on the front of the box: Do not use in a standard incandescent outlet. I didn't pay much attention to the box until I was already home, and had tried to use them. The oversized bulbs were made for bigger fixtures (Outdoor lights mostly) and I was skeptical so I didn't even bother.

As far as a box goes, I'm not really sure how to make one.

What I ended up going with was actually an unfiltered UV reptile light found at a pet store. I looked on the box and it had a graph showing the wavelength of UV light and surprisingly it was in the right range, 350-420 Wavelength (nm). I was worried at first about the wattage being so low, but, I took a risk and purchased 6 of them, hung them above my screen, and it worked fine.

I hope this helps some.

RichardGreaves · June 19th, 2007

Quote:

Originally Posted by Paul204


	how can i tell if this ballast and this bulb will be appropriate for screen making? 1000 Watt Metal Halide Ballast Wired RTU - Metal Halide & High Pressure Sodium Ballasts 1000 watt Sylvannia MH Clear - Metal Halide Bulbs

If the energy output by the bulb is UV-A range between 350 and 420 nanometers.

Yes, sunlight has UV-A, but I see nothing in the bulb section at the links you showed that mention UV-A.