Author Topic: The Contraption 28: UV Exposure Box  (Read 338 times)

Francois

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The Contraption 28: UV Exposure Box
« on: March 21, 2024, 08:58:12 PM »
This project started during the dark dull days of winter. I really wanted something new, exciting that I've never done before. I was bored and a bit depressed by the ever present dark clouds that covered the province. I suddenly got an idea! Making cyanotypes. There was something I had never really done before. But it posed a big problem; how do you do a UV based process when it's freezing and dull outside? Lets just say that taking a couple of days to expose just one negative didn't appeal to me. And not having control over the exposure didn't make sense to me either. So, it left me with only one option: make a UV light box.

So, like any good maker, I went online to see what others had done. While I loved the idea of using LED strips to generate the ultraviolet rays required for the process, there were a lot of things about what I saw that I didn't like. First, all the devices I saw were bulky to store. They all relied on an external timer to control the exposure. And when not in use, the LEDs were left exposed and could be damaged. So, how could I make this compact, clean and easy to store?

My first idea was making a shallow box that contains all the electronics that can be lifted-up on legs and that worked a bit like a Transformer toy. Now there was a start. Then I thought of making a protection panel that goes under to protect the LED. That was an idea, but I thought that if I could include a printing frame it would make things really convenient. I had a plate of glass that I had been holding on to for decades, so that was the start. I now knew what size to make the thing. Now came the electronics... and the Aliexpress shopping. First came the LED strip. looked around and got the cheapest UV LEDs I could get. While they are not the optimal wavelength for cyanotypes, I knew that it would just take a bit longer to expose them. I saw online that someone had success using a 60 LED per meter strip. When doing the shopping I discovered that I could get 120 LED per meter ones for not much more. This is where I hatched a cunning plan! (this makes me feel so much like Jeremy Clarkson...) If I make two LED paths that interlace one another? I could then use one as a regular exposure thing and add a switch that powers the second one if I want a boost!
So, the order was put for a 5 meter strip and the waiting game began. Fast forward two weeks, I finally have the strip. I tested it with a small power supply and it works... but when I calculated the total required wattage, I instantly knew that my small wall wart didn't stand a chance of surviving. So I put in an order for a new power brick, but this time I chose one that had plenty of spare power (200 watt) and a small programmable digital timer like is used on industrial machinery; hoping that those fine Chinesium electronics would not catch fire. And waited another two weeks, checking the tracking information on a daily basis. I was lucky that it didn't come on the slow boat. 😊

Once the parts were in, it was time to get to work planning and building. Lucky for me, my dad was bored stiff in front of the TV and was ready to do anything to get out of that rocking chair. So I knew I had the hands for the job.

I first had him make the exposure frame. Then, we mocked the build on the workbench in order to get some dimensions. While it took some time for him to catch-on to what I wanted to achieve, once he got the grasp of things, we were off to the races. It was nice to have some design collaboration instead of the usual arguing. Cutting, gluing, assembling, staining and varnishing was the name of the game. It took a bit over a week to build, but I now know that it's robust and well designed. Easy to repair if need be and unique.

Once it was built, I couldn't wait to try it out, so I took out some old sunprint paper I had bought about 10 years ago, got an old 4x5 negative I had shot on a 3D printed wide angle pinhole camera, and put the system to the test. I gave it a randomly chosen 15 minutes exposure (it was too much) and powered the device. It glowed in a beautiful but eye hurting blue. It also showed all the crap I had spilled on my darkroom counter (who knew that dried developer glows under UV light?).

And to my surprise, it worked extremely well. So, I now just have to put an order out for a cyanotype kit...

Here are a few pictures of the contraption.
« Last Edit: March 21, 2024, 09:08:23 PM by Francois »
Francois

Film is the vinyl record of photography.

Francois

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Re: The Contraption 28: UV Exposure Box
« Reply #1 on: March 21, 2024, 08:59:14 PM »
And here are the rest.

I hope you enjoyed this project.
Francois

Film is the vinyl record of photography.

leanne

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Re: The Contraption 28: UV Exposure Box
« Reply #2 on: March 21, 2024, 09:28:29 PM »
That's amazing François. Is this strong enough for other types of alt processes? Salt prints and platinum/palladium etc? I'd love to go down that route, and this think looks so much thinner and storable than the huge UV tube light boxes that I've seen.

Francois

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Re: The Contraption 28: UV Exposure Box
« Reply #3 on: March 21, 2024, 10:39:15 PM »
I'm pretty sure it is, especially if I put all the LEDs on.
In the end, it's just a matter of increasing the time.

It will also come down to the type of negative used. I plan on using digital negatives that are custom calibrated to the process in order to get the best results.
I've already tried using transparencies in my printer but it doesn't lay enough ink to get a good density. So I will have to use some vellum negatives... but that will increase exposure times. I just hope I won't have to resort to using the boost mode all the time. But if I do, it will at least be there.
Francois

Film is the vinyl record of photography.

Pete_R

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Re: The Contraption 28: UV Exposure Box
« Reply #4 on: March 22, 2024, 11:03:46 AM »
I've already tried using transparencies in my printer but it doesn't lay enough ink to get a good density.

It's worth experimenting with different colour ink as some is more opaque to UV than others. If you print blocks of colour then make a print you can see which colours block the UV most. I found it made quite a difference. I don't remember which colours were best though - too long ago.
"I've been loading films into spirals for so many years I can almost do it with my eyes shut."

Francois

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Re: The Contraption 28: UV Exposure Box
« Reply #5 on: March 22, 2024, 01:28:03 PM »
I print in high quality mode which combines all the colors to get better results. But even with that my old HP printers struggles to lay enough on the transparency as I can see the individual dots.

Yellow should be the most UV blocking color in the set.

I tried running the transparency twice through the printer but that feels like a waste of ink...
Francois

Film is the vinyl record of photography.

Pete_R

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Re: The Contraption 28: UV Exposure Box
« Reply #6 on: March 25, 2024, 05:33:34 PM »
It's worth doing the test because, if you print black in colour mode it will use equal amounts of each colour. If you print a colour the amount of each ink will vary and the results may be better. You need a test chart like this



You need the varying densities because some colours may produce a more linear result than others though you can compensate for that to some extent by adding a curve before printing.

I think I still have the test print I made somewhere but we're all packed up ready to move house so no chance of finding it at the moment.
"I've been loading films into spirals for so many years I can almost do it with my eyes shut."

Francois

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Re: The Contraption 28: UV Exposure Box
« Reply #7 on: March 25, 2024, 10:26:01 PM »
I think I still have the test print I made somewhere but we're all packed up ready to move house so no chance of finding it at the moment.
I don't blame you. Last time we moved it took us forever to find all our stuff. And now, there's not a chance that we would be able to move without a big truck.

I think there is a similar chart on Alternativephotography.com.

I plan on making an adjustment curve, doing a regression and make an imagemagick script to take the pain out of applying curves one by one.
Francois

Film is the vinyl record of photography.