LED UV Light Box: Build Your Own for Under $150

[Fr. Mark]

I put the ballasts outside on mine. I used 6 18" t8 tubes. I've never printed bigger than 8x10 yet but I had in mind 14x17 when I built it.

[denverjims]

So, I have a few more questions before I start planning my own UV exposure box. As I said earlier, I am not very good at building things, so if my questions seem dumb is because I am completely out of my element here.

1. I don’t want this box to be tall (?). I’ve seen some boxes that, looking at them from the front, are simply too tall, a couple of feet tall. I am trying to keep mine only a few inches tall. The Arista boxes are, I believe, 7 inches tall. Sullivan & Weese’s box is 8 inches tall. How much space should the ballasts have? I mean how much space should there be from the top of the ballast to the “ceiling” of the box?
2. How much space should there be from the lights to the bed where the negative/paper will rest?
3. How does one determine how many lights should there be in a given area? Take the example offered by Sullivan & Weese in The New Platinum Print (pg. 86). Their exposure area is 18”x20”, and they installed 12 eighteen inch candles. How did they determine that twelve would be enough lights? Or is twelve just a random number? If properly spaced, could I pick to do a box like theirs with only 6 candles?
4. How does one settle on the wattage for the candles?
5. Is the fan absolutely necessary? Some people here have said that they built boxes without fans.

If I think of any other questions, I’ll ask later, for now, this is it.

Thank you.

1. & 2. The main problem is that if the paper is too close to the bulbs, you will get stripes due to the uneven illumination. Because of the inverse square law, the closer you are the greater the differences in illumination % is between where the bulb is closest to where the spaces between bulbs provide little UV. I chose about 5 1/2" from the bottom of the bulbs to the floor of the box and that seemed to be OK. It was about the minimum of the distances that were recommended.

Also, you need to take into account the thickness of the holder which will hold the sandwich of the negative and the sensitive paper. If you are just using a piece of glass then it will not be very thick but many of the commercial types (like those available from the Formulary) raise the paper an inch or more above the floor of the box. This means the box has to be that much taller.

Finally, if you put the ballasts outside the box, it can be shorter. In most builds I've seen, including mine, the ballasts are inside the box and, so, add to the height. Putting the ballasts inside keep you away from the heat and the potential for contact with the electrical connectors.

3. 'jp' answered that one pretty well. I chose 12 lamps as they seem to cover 16x20. There is also the issue of the tombstones having width which limit how closely you can pack them. I have seen some designs which offset alternate bulbs which allow a little closer packing. Of course, the closer you pack them together, the more heat generated in a small space - hence increasing the need to dissipate the heat with a fan.

4. Most bulbs available are what they are in watts (most common T8's seem to be 15). You pack as many into the space as you can (to minimize the exposure times) and that's the wattage.

5. If the ballasts and the bulbs are inside the box, you will be well served to have a fan. A lot of heat will cook the electronic ballasts (and they do get hot). That is why so many fluorescent light fixtures are made of metal. The fixture becomes the heat sink to dissipate the heat. But inside a wood box (the most common material used and a fairly efficient insulator) the heat normally can't move away fast enough by itself. Also, the bulbs generate a fair amount of heat by themselves. Too much heat could affect the chemistry on the papers. A fan is the normal solution. Again, if the ballasts are outside the box, it will decrease the amount of trapped heat.

Hope this helps some, Jim

[denverjims]

macandal,
I had not looked at the pictures that 'jp' linked to when I made my previous response but I wanted to point out that he used that offset alternating technique I spoke of in mounting his bulbs which allowed him to pack more bulbs into a smaller space. This gives more light and some more even coverage.

My mounting was side-by-side as you can see by the pictures I posted with my project build (linked to in a previous posting in this thread). This did not allow me to pack the bulbs as tightly as 'jp' did but, since I was trying to cover up to 16x20, I would have required an additional ballast if I added any bulbs. I felt that the decrease in exposure time was not worth the additional cost. I had calculated that my distance from bulb to base was sufficient to avoid bands / stripes even with the slightly increased center-to-center separation of the bulbs over the other technique.

[macandal]

Okay guys. Thank you for all your answers/suggestions, but I'm a bit confused here. jp says, in post #70, in relation to the ballast/fan question, that it does not get very hot, and, I'm assuming, he's suggesting that I don't really need to add a fan to my box. Yet, others have said that it does indeed get hot and that a fan is necessary. Which is it? Given that the exposures will only be a few minutes long, do I need the fan or not?

Thank you.

[Tin Can]

You may not get an answer. This forum usually avoids any electrical advice. Liability comes to mind.

We are seeing even boxed new items burst into flame.

DIY is a solitary pursuit, best accomplished by through personal research until the researcher is sure of their capability.

Note that someone here stated fluorescent bulb fixtures are usually metal, probably for heat sink and fire resistance. Even metal can burn...

I recommend everybody have at least 2 fire extinguishers of the proper type for their situation.

I also recommend unplugging from the wall as much as you can and inspecting all electrical devices as often as you can.

Safety First.

I have put out enough home and industrial fires to fear them. Lost 2 family to house fire recently.

I was trained yearly on big outdoor gasoline fires for my indoor job.

I am not a Fireman nor emergency worker.

[sanking]

Okay guys. Thank you for all your answers/suggestions, but I'm a bit confused here. jp says, in post #70, in relation to the ballast/fan question, that it does not get very hot, and, I'm assuming, he's suggesting that I don't really need to add a fan to my box. Yet, others have said that it does indeed get hot and that a fan is necessary. Which is it? Given that the exposures will only be a few minutes long, do I need the fan or not?

Thank you.

First, how do you know your exposures will be short? With certain processes and types of negatives exposure times can be very, very long.

Why not think of it this way? Installation of a fan is a relatively simply procedure that may improve the safety of your light box and help to give more consistent exposures by keeping the temperature down. There is absolutely no down side to a fan in a light box, except the possibility of a mistake in wiring.

Yes, you may be able to get away with no fan, 1) if your frame is made of metal and can serve as a heat sink, 2) if tube spacing is far apart, and 3) if exposure times are always short. If you look on ebay you will find that many of the exposure units sold for the screen printing industry fit this description.

However, if you are making a box with a wooden frame, with very close spacing of the tubes, with the ballast enclosed and not well ventilated, and your exposures are long, there can be enough heat build-up to reduce radiation and slow down your exposures, and cause enough excessive built-up of heat to be a major safety issue.


Sandy

[jp]

Given that a kid's easy-bake oven is basically a box with a 100w bulb in it. Given that a coffee burner (not the coffee maker element) is generally a 60-100w heating element, and we are making boxes that consume similar power, it makes sense to have a ventilation fan whether it's needed or not. Err on the side of caution, not how you exactly intend to use it.

I ran mine for a few hours after I built it to verify it didn't get warm or malfunction. If you think you are only using it a few minutes at a time, consider the results of if you left it on by accident overnight. Mine is also plugged into a gralab 451 timer which starts up off, and I leave it on a turned off power strip when not in use.

I think traditional fluorescent fixture are metal because the original magnetic ballasts used to sometimes self destruct and the metal was good safety. Contemporary electronic ballasts don't fail as dramatically.

[denverjims]

"A man oughta do what he thinks is best." John Wayne; "Hondo"

...women too.

[j.e.simmons]

I only print 8x10 and successfully made a light box with BLB CFLs. They have ballast built in, so the only wiring required was between common flush sockets. I left the ends of the box open, so I have little heat buildup, even with some of the long exposures required.

[denverjims]

I only print 8x10 and successfully made a light box with BLB CFLs. They have ballast built in, so the only wiring required was between common flush sockets. I left the ends of the box open, so I have little heat buildup, even with some of the long exposures required.

Great. Didn't know that they existed. Sounds like a better solution.

That's the thing about technology changing as rapidly as it does. Any advise you receive today about what a good solution might be can be made obsolete by another new product being made available to us. Someday soon, hopefully, LEDs will be made more permanent as UV light sources and it will, again, be the way to go. With their small emitter size, efficiency and low heat output; it would be perfect. That is, until the next gizmo comes out.

Best, Jim