UV LED Exposure Boxes

[Tin Can]

Good advice Sandy

I just ordered the 365 at your link to test

Thank you

Jim

UV tube bank is indeed a reliable exposure source for alternative processes, and in the past tubes of optimum wavelength have been available. However, replacement tubes are becoming increasingly difficult to find in some cases. But as long as your unit is working keep going.

UV LED light sources do have an advantage or two for some printing processes in that the individual leds tend to produce a more point-source type light than tubes, which give a very diffuse light. In the case of carbon transfer printing my LED unit gives prints that are noticeably sharper than the same unit with UV tubes.

Unfortunately, most of the UV LED lights for sale use the less expensive 396 nanometer leds, which is not optimum for most UV sensitive processes which typically work best with 365-75 nm light sources.

Some people have gotten good results by ganging up three or more UV flood lights, which give fast exposure and good coverage at about 24" with quite sharp results. But if you do this make sure to choose the 365 nm flood as they are much more efficient than 395 nm.

https://www.amazon.com/Everbeam-Blac...22493665&psc=1

Sandy

[sanking]

Good advice Sandy

I just ordered the 365 at your link to test

Thank you

Good luck with your tests.

Attached bellow is my summary of testing with one of the 365 nm Everbeam floods. Just for the record, my tests were with a 100 watt Everbeam, which are a bit harder to find than the 50 watt units.

Sandy

UV integrators are useful in printing, and also very nice to have if you need to compare UV output of specific light sources. I have some older Olix light integrators that I use in regular printing, and also own a PPM-1 meter that I use to compare different light sources.

I had the chance during the past several days to work with one of the 365 nm 100-watt UV floodlights, sold by Amazon with the Everbeam brand. I made a few quick comparison tests using the PPM-1 to compare output in various situations.

First, I measured useful radiation on center at 12", 18" and 24". Output decreases with distance more or less in accord with the what one would expect with point source light, i.e, every time you double the distance between the light source and the exposure plane, exposure times increase by 4. So here are the results.

12" Center of flood to exposing plane -- 1000 second gives UV Dose of 6400 -- Would print evenly about 8X10" in size.
18" Center of flood to exposing plane -- 1000 seconds gives UV Dose of 2744-- Would print evenly about 11X14" in size.
24" Center of flood to exposing plane -- 1000 second gives UV Dose of 1700 -- Would print evenly about 16X20" in size.

Other comparisons.

1) Measuring UV dose outside, on a sunny day in open shade, facing north at 12 noon on December 18, at north latitude 34º35 minutes, 1000 seconds gave UV does of 1820.

2) My regular Ryonet LED printing unit, with 385 nm leds, 1000 seconds gives UV dose of 6675. With this unit my typical exposures require UV Dose of about 5000, or about 750 units/seconds.

The 100 watt 365 nm flood is about 3 lbs. in weight, has an overall size of about 8X10", with the leds in an area in the center about 4.5" X 3" in size. There is good heat shield on the back but you would still need to cool the unit with a fan blowing over the heat shield to keep the unit cool as radiation decreases with heat build up. Combine it with a contact-printing frame and I think you have a pretty efficient UV source for making small and medium size prints. And one could also weigh the possibility of ganging up 4-6 of the floods for wider coverage. The most efficient flood for printing carbon with dichromate sensitized tissue would be the 365 nm leds, but 385 nm would be less expensive and probably almost as efficient. For DAS you would definitely want the 365 nm light.

BTW, have a look at the linked video, about salt printing, produced by the George Eastman Museum. https://www.youtube.com/watch?v=VDfd...ature=youtu.be
In the video you will see that they are using what appears to be a couple of small UV flood lights ganged together for the exposure.

[martiansea]

I've done many good 8x10 prints with a single 20w high powered UV LED hanging about 12" away with a standard Graylab darkroom timer to control it. This is the quickest/easiest/cheapest solution next to using the sun. I think most pre-fab UV exposure boxes are drastically overpriced, unless you put a premium value on rudimentary woodworking.

The one in OP's link is intended for screen printing and the vacuum sealing system it uses is specific to what you see in screen burners (the rubber that forms around the screen frame to hold it) and is unnecessary/inappropriate for vacuum sealing paper+film, in my opinion.

[Barry Kirsten]

I have just built the unit shown, using 395nm LED strips from: https://www.ebay.com/itm/25342418478...UAAOSwhlZYsvun

I bought 2x5m rolls cut into 0.5m strips spaced 1cm apart and used two 12volt 14watt power supplies, available from the same eBay store. I haven't had time yet to test its output yet, but am hoping it will give fairly short exposure times. I know of others who have made this setup and it seems the output is comparable with sun exposures.

[Tin Can]

Sandy and all

I have the PPM2 meter and an UV AB meter for testing

[pmviewcam]

Barry

i have also just built the same setup, 10m of 395nm, 160 watt power supply. I have found so far that my BLB tubes are still faster than the 395nm LEDs for VDB/Cyanotype, and also for Ziatype; haven't tried salt printing with it yet. I am going to replace half the LEDs with the 365nm wavelength to see if that speeds up the exposure time. If that does, I will replace the rest of the 395 strips. My LEDs are about 150mm above the printing frame.

Cheers, Peter.

[Barry Kirsten]

Hi Peter,

Thanks for sharing your experiences. I'll do the same if I find my unit too slow. Do you mind sharing the source of your LED strips? My source apparently has 365nm panels only, which is a more expensive alternative.

[pmviewcam]

Barry,

There are some available in Australia, but for heavy duty prices. The best I have come across so far is at Aliexpress. If you do a search there on "365nm ultraviolet led strips", there is one for USD$95-00. That is the one I will be getting. But I also just picked up a 50w Everbeam UV flood for testing ($60 from Amazon AU). I am going to use it for UV photography, but thought it might print much faster than the 395-405 LEDs. I was going to try some VDBs this week.

Cheers from Canberra, Peter.

[Barry Kirsten]

Hi Peter,

Thanks for all the information. Re the Everbeam flood on Amazon, I think that's the same or similar to the one Sandy recommended last year on the Carbon forum. At the time, I looked on Amazon and found that they were unavailable in Australia (no surprise there). I must get to test my UV box and see just what speeds I can get, then I'll take it from there. At the moment I have a pesky problem building an enlarger timer. I've re-built the circuit several times yet success eludes me. I have an Ilford multigrade head on one of my L1200s, so it's not critical, but I don't like to be beaten and that's why I haven't tested the UV box yet. Cheers,

Barry