Converting Lightbox to UV box

Rob Skeoch · Dec 10, 2007

I hope to make a UV light source.
I'm starting with a box that used to be a lightbox. The inside is 36 inches long and 13.5 wide and holds two tubes. I had a piece of plexiglass on it to soften the light when viewing negs. It's 4.5 inches deep.
My plan is to replace the two tubes with a UV or blacklight tube from the hardware store. Add a timer to the plug, remove the plexi and I'm off to the races.
Here are my questions.... will two tubes be enough? .... without the plexi softening things will I get uneven exposure? ... am I missing something major but don't see it? .... am I way out in left field on this idea?
-Rob

glbeas · Dec 10, 2007

Two tubes are nowhere near enough. I made one with cheap black lights from Wal Mart, I got six of them and mounted them shoulder to shoulder in a box and plugged them into a power strip so I could plug them into a Gralab timer. It covers 8x10 pretty good. This was constructed to place over a contact frame.

FredW · Dec 11, 2007

I would second that two tubes will not be enough, I built my own light box of 8 tubes, mounted into a wooden box, and it would easily cover a 16x20 print. Just been using it to print some 11x14 negs, and its very even.

Akki14 · Dec 11, 2007

Buy a UV facial tanning unit. It's easier. Not sure they have them where you are but they seem fairly common from Philips in the UK and the rest of Europe too. Buy'em secondhand, they're very cheap then, much cheaper than trying to build your own or even the cost of buying the tubes themselves. They have a silver-y plastic reflector behind the tubes and I've not had a problem with banding even with the frame only an inch or so away from the bulbs.

Whiteymorange · Dec 11, 2007

Akki14 said:
Buy a UV facial tanning unit. It's easier. Not sure they have them where you are but they seem fairly common from Philips in the UK and the rest of Europe too. Buy'em secondhand, they're very cheap then, much cheaper than trying to build your own or even the cost of buying the tubes themselves. They have a silver-y plastic reflector behind the tubes and I've not had a problem with banding even with the frame only an inch or so away from the bulbs.

I just built an exposure unit using one of these lamps for polygravure printing. The museum based class where I was working had one that worked fine for small plates, with exposure times for KM73 plates at 40 seconds or so.

The one thing that is somewhat limiting with these is the size - the bulbs are 9" long and the unit is about 9" wide. Has anyone tried backing off and working with larger negatives? The distance from the plate to the lamps in the school unit is a bit less than 4" and I've never tried anything bigger than 8x10.

You also have to be careful with these to expose away from your eyesight, since they are strong in UVA light - not good for the eyes, I think. A box with the unit mounted in the bottom and then inverted onto a plate glass over the negative seems to work fine.

TheFlyingCamera · Dec 11, 2007

I'll give another pitch for the home-built UV unit I have - six blacklight fixtures from Home Depot (made by GE), run through a surge strip. I've got enough coverage from these tubes to properly illuminate a 12x20 or 14x17. Cost? About $18 per fixture, plus another $20 for the surge strip. The fixtures include a BLB bulb.

michael9793 · Dec 11, 2007

every unit I have seen out there that uses blacklights or any type of uv tubes always uses 8-12 tubes. If 8x10 use smaller tubes keeping them about a half inch apart so you can remove them. There is a site I can't remember it right now maybe someone else can, it is something eye.com. It is in Arentz newest revised book under how to build a UV Box.

mike

JBrunner · Dec 11, 2007

Perhaps you are refering to unblinkingeye.com?

By all means build or obtain a UV box, and yes, many more than two tubes. The exposures still seem to take forever with six. If you find that you really enjoy UV contact printing processes, consider looking for a Nuarc 26-1k or check out this APUG sponsor:

http://www.amergraph.com/products/pages/ULF-28.aspx

These things really are the bomb.

TheFlyingCamera · Dec 11, 2007

In the grand scheme of things, a 6-8 minute exposure is a long way from forever. Honestly, I'd rather have it in that time frame so if I need to adjust exposure, it is easy to control given the lightsource.

Now, with one of those NuArc units, that's a different story as they use light integrators so they always output the same amount of light, and vary the time to accomplish it.

Converting Lightbox to UV box

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