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Discussion Starter #1
Hey Team!
I am having some issues burning screens using a home made lightbox that I bought used. It has 6 50watt flourescents bulbs and is about 12 in away from the screen. The screens are 1 on 1 coated using Ulano QTX. I was burning screens before using a 250 watt photobulb and had good results burning for about 45 min. That bulb died so I am trying out this homemade setup with the 6 50watt fluorescent bulbs and am running into issues. Anyway, can anyone suggest to me how long I should burn using this setup?
 

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A step wedge test will tell you for sure but mine is around 5 minutes. I have a homemade unit as well but I use different emulsion so the best way to no for sure is the step wedge test.
 

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Hey Thanks cross your heart! Well some issues where when exposing for around 25 mins was the rest of the emulsion is washing out and then when I do 45 min some emulsion won't wash out in the image area. The times I was trying varied but results did not, either all emulsions is rinsing off or not rinsing out at all and when washed for a while all the emulsion starts to rinse away. It took a little time figuring out the photo bulb and that worked great but I wanted to utilize my light box but it has given me nothing but headaches. Also does exposure time vary between the qtx and the swr-3? I might just go back to the single 250 watt photo bulb.
 

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Thanks guys! I am using florescent bulbs, do I need black light uv bulbs? I have seen exposure times that are like 5 min and even like 1-3 min and if I do anything under like 12 or even 25 mins it just does not work. I have even had emulsion washing out out up to like 40 mins. and anything longer leaves emulsion in image area and then will still wash away in the exposed area. Does anyone have experience using florescent bulbs? How do i do the step wedge test and what woud the time intervals be? What would the time range be?
 

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My home made light box has 20" super UV reptile lights from Pet Smart. I've got a bank of 8 0f them about 5" under the glass that the screens rest on. Exposure times run 2 minutes 45 seconds using QT discharge emulsion. It holds 6 point times, and 190 ppi indexes without undercutting. They never wash out, and also i goofed up and exposed for 5 minutes once, QT discharge was so forgiving I still used the stencil. :)
 

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My home made unit has six 24" bulbs, they are 6 inches from the glass, and I use regular T12 flourescent bulbs from Lowes. my burn time is 5 minutes. Again I use a different emulsion and yes the type of emulsion plays a role as well from my understanding.
 

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Just from my research here on the forum, your exposure distance is to much, between 3 and 6 inches in the norm for that type of light. Also regular florescent bulbs are poor uv sources.
 

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You should be using a unfiltered uv bulb works great at around 6 inches or so. You can get these at electrical supply stores they are not very expensive. You can also get a nice tan if you want as well lol
 

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Also regular florescent bulbs are poor uv sources.
For many years now I have been using standard T12 flourescent bulbs out of Lowes for exposing and every single time it is on point at 5 minutes. I have no idea why people think they are not sufficient.
 

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Homemade exposure units are all about trial and error. Ideally you don't want to be changing anything other than the exposure time each time you test, so once you're happy with your UV source and distance to the screen, stick with it. You also want to make sure you're coating your screen the same way each time (i.e. only on one side, with the same amount of chemical, etc).

Once I had that sorted out I just sat there with a notebook, pen and stopwatch. My first tests were to find the extremes - how much time is too little, how much is too much. Then I just narrowed it down from there with a bunch more tests.

One thing I found difficult with the homemade unit was the washing out part. My buddy and I wrecked his parents downstairs shower trying to wash all the screens out. Make sure to have a suitably prepped area to do it and a source of relatively high pressure water.

Good luck - the process is tedious at first but once you get it you'll be good to go.
 

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My home made unit has six 24" bulbs, they are 6 inches from the glass, and I use regular T12 flourescent bulbs from Lowes. my burn time is 5 minutes. Again I use a different emulsion and yes the type of emulsion plays a role as well from my understanding.

I agree with Katrina...I have the same basic set up she has (Got the idea from her sometime last year....Thank You by the way) and my exposure time is 5 minutes 35 seconds using photocure blu. Even the guy at my supply house was amazed at the detail I get in my screens. He was skeptical at first, but he's seen it in action now and he was impressed. Try using a more sensitive emulsion and maybe that will help.
 
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