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Building my own exposure unit...SUGGESTIONS???

3486 Views 22 Replies 10 Participants Last post by  selanac
hello all, i am building my own exposure unit based on Screen Printing Exposure Unit
I didnt do it EXACTLY like that, as i dont think id use the tracing lights etc, BUT i cant tell from his vid and im wondering if any of you know, does the bottom, under the lights need to be sealed (BOXED IN) as you can see from mine, its open right now, also has anybody built a similar exposure unit to this? how long should i be letting my screens burn, these are 20wt black lights...here is what ive got so far...

what else do i need to burn my screens? do i cover with glass or black paper or what? any help is greatly appreciated.
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You need unfiltered black lights, the ones you have won't work
You need unfiltered black lights, the ones you have won't work
i bought the ones he stated in the video, anyway, unfiltered you say? where can i get those? do you know if the bottom needs to be sealed?
Unfiltered black lights are not black, they look like ordinary fluorescents until they power up, same thing they use in tanning beds.
I would seal the back and paint the inside white to increase the amount of UV reaching your screens.
You need a piece of foam or a board covered in black material to set on top and weight to insure good contact of your film to your screen to reduce undercutting of the stencil
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awesome! thanks, ill order those now, and ill seal up the bottom.
i just have a couple more questions, the foam or wood covered in black, can you explain that a little more ? what exactly should i use? wood or foam? ive heard people set glass ontop as well?

my other question is about emulsion, using the set up i have, what would be the most effective emulsion to use? what are my approximate exposing times? like 10 minutes or shorter like 2-5?
1000 bulbs screwed me. They kept telling me they were coming and they never came.

I'd go to a local lighting store or two.

Also, many companies stopped carrying T12's and went to T8's.

Don't know if you NE more fixtures or not.
I have no experience with 1000 bulbs so I can't vouch for them, was the first link that came up when I googled the bulbs.
Basically you need something smooth & flat to fit inside the frame to push the screen into contact with your film, a piece of laminate covered particle board would also work. The heavier the better, stack some books or other weights on it to help.
You want to cover it in black fabric to keep any stray UV from bouncing around and exposing other parts of your stencil.
All emulsions expose @ different rates, pick one and get a stoffer strip and do an exposure test to determine the optimum exposure time
topbulb.com has them. I put foil around the inside of mine and made a vacumm lid. Every emulsion burns different so you will have to figure that out on your own. I have plate glass on mine and make sure the glass doesnt have uv in it. People never believe me on here but I can burn a screen in 30 seconds with those lights and Saatti Textile Pv emulsion from one stroke inks.. That stuff has a year shelf life and no mixing. Good halftones too.
Here is a link to my box build:
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Building a lightbox saves so much time, I went from a halogent work light with a 12 minute exposure time to a florecent box, I think its 8 4 footers in their and I can now burn a screen in 40 seconds.
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I have 6 tubes in mine, enclosed box, 1/4 " unfiltered glass. use a piece of HEAVY black cloth folded in two then a block of foam cut to fit INSIDE the screen ( I think it helps with wight distribution.). On top of the foam a piece of plywood then the weights. I use pc-701 and have had no problems with halftones or spot screens.
What is the purpose of the foam? What is pc701? & what sort of weights?
The foam helps press the mesh down to the stencil evenly. P701 is the ulsion we use The weightsare nothing special, we use gallon jugs of water
4 of them.
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He meant Emulsion. Also the foam is to hold the Film in place. The weights hold it down so you don't have air between the Glass and piece of Film.

You didn't ask, but the Black Cloth keeps the excess light out.
I dont use foam, I use a big piece of card board and 4 bricks or big books. I love my unit. I coat it air dry it in my screen rack with the belp of a box fan burn it, washout then dry the screen on my conveyor. Total time from coati.g to ready to pri.t is around 20 minutes.
I have a question is there a bulb equivalent in T8 to the ones you guys mentioned, cause the fixtures i got today only support 32 watt T8
Where did you buy the individual lights? I'm confused on what to get. Is it just something like this:

Fluorescent Economy 1-light 18 in. White Under cabinet light-VTR15-P at The Home Depot

, then replace the white bulb with an unfiltered black light bulb from top bulb? What wattage are your bulbs?

I saw another set of plans that use halogen work lights (500 watt), but I'm assuming I'll get better results from blacklights?

I'm a total newbie, so sorry for my ignorance here.
I get the best results from Halogen 500 watt shop light. 12 inches above the screen. 1/4 inch glass. Expose for 3.5 minutes.
I get the best results from Halogen 500 watt shop light. 12 inches above the screen. 1/4 inch glass. Expose for 3.5 minutes.
Emulsion type? Just wondering since that's a familiar setup for me.
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