Screen Printing Forum

So I've decided to try building an exposure unit, and I feel pretty confidant about everything except bulbs. There's so much information out there, and it's all so vague!

My main source of information has been roger jennings' video on building exposure units (found at http://www.youtube.com/watch?v=x9NrndxeCJ4). He mentions that he would use at least a 1000 watt bulb, and that metal halide would be best, but that one shouldn't even bother because it's so hard to find. However, I just hopped on ebay and found a 1000 watt metal halide bulb for $15.00. I'm pretty confused! Can anyone clear this up for me, or give me a recommendation on a bulb that has worked well for them?

Thanks,
L

A metal halide bulb works well as a cheap source. they need a ceramic holder, refector, ballast and transformer - there are many setups used for hydroponic growing (read growshows up here in Canada) that have all this wired together. I bought a new set for about $240. You could pay less. the bulbs are probably the cheapest part.

Metal Halide are reasonably available. Often they are taking them out of buildings/parking structures/gymnasiums, etc and replacing them. They require a ballast (which is often mounted to the top of the light fixture/reflector assembly) to start them and since it takes a while to obtain full intensity of the light you'll need a "shutter" of some sort. I know of screen printers that use a 400w bulb in a fixture hanging over their exposure table and they've mounted what amounts to a piece of metal on drawer slides under the light fixture to act as a shutter. If you want a more commercially made industry-specific metal-halide light source, they are available on eBay, craigslist, etc. That's where I got mine. It's not "huge" in that it's only 1000w, but I only expose 1 20x24 screen at a time. You might try a search on eBay, etc. for "OLEC" or "NUARC" and see what you come up with. Also if you go to The Screen Printers Message Board and do a search for metal-halide , you'll see a great deal of information

Just posted this in another thread, but thought it might be useful.

http://youtube.com/watch?v=x9NrndxeCJ4