Light box

Richard Sullivan (richsul@roadrunner.com)
Wed, 17 Jul 1996 01:36:56 -0600

Macy Garcia wrote:

>Regarding building a florescent light box, what distance are you (or
>anyone) using between the light source and the print frame? Do you use
>any diffussion over the bulbs to even out the light? Would this control
>contrast somewhat as with a diffused light source?
>

The best set up I have found is to use bug zapper UV's. These are the
replacement bulbs for those gizmos you see in butcher shops, etc. that have
the purple bulbs inside and a round grid that fries the bugs as they try to
get to the light. The bulbs come in 20, 40 and 80 watts and they are in the
shape of a loop with four pins at double end of the loop. It's just one long
bulb folded in the middle. The pins on the ends correspond to the pins at
the two ends of a straight unfolded bulb. It'll makes sense once you look at
one. The 40 watt ones will work on a standard 40 watt ballast, just follow
the diagram on the ballast in wiring it up. Use a soldering gun to attach
the wires to the pins. Put shrink tubing over the joints. I made a shallow
box and hung the bulbs sideways inside using coat hanger wire looped around
the bulbsand thru holes in the top to hold them in. I drilled more holes in
the top and screwed the ballasts down on top and wired them up through the
holes. (When you're finished make up a UL sticker to put on the side<g>)

The bulbs should last quite a while so soldering is a good way to go, though
you'll need a heavy duty gun to solder the pins to the wires. A 40 watt bulb
is about 10 inches long. I think the name of the game is watts per inch of
bulb, and in this case you're getting 40 watts of uv in a pretty small
space. My box is about 20 inches square and has 4 bulbs in it and I get
times with pt/pd of about 6 minutes, and my negs are usually dense.

Of course you can zap yourself with a rig like this if you are not careful.
The best way to go would be to build a separate chamber at the top for the
ballasts and put in a fan.

Another tip, due to the way American capitalism works you can sometimes buy
ballasts cheaper by buying a 2 bulb shoplight fluorescent and removing the
ballasts than in buying them separately. Also, most 40 watt ballasts run two
bulbs.

I shudder to think what a rig like this using 80 watt bulbs and ballasts
would do.

You can get the replacment bulbs in the garden section of big warehouse
style hardware stores by the way

Dick S.

Bostick & Sullivan
1541 Center Dr.
Santa Fe, New Mexico
87505