It's been 28 Years since I did some Screen Printing in College. I have 3 screens that I'm trying to make but I'm lost. I built a Screen Exposer Unit that is in Scott Fresners Book but larger. The Home Depot near me didn't have any 2 foot Strip Lights so I had to go to 48". Since they are so long I had to increase the size to 52" x 23". I put in 2 double strips and GE 40 watt Gro Bulbs. I am using screens that are 24" x 31" 230 mesh counts. I bought Ulano RLX emulsion because I have to do 100 signs and 150 T-Shirts Front and Back. Our Event is Tomorrow. I used 3M Inkjet Transparency Film. This morning I tried to expose for 5 minutes and then 5 minutes 30 seconds. I blew both screens and the entire screen washed out. I'm near Atlantic City NJ and looking for someone local that I can pay to burn my screens if I can't do them myself. ANY help would be nice. I would like to do them myself but am open to suggestions. Please Help.
It's been 28 Years since I did some Screen Printing in College. I have 3 screens that I'm trying to make but I'm lost. I built a Screen Exposer Unit that is in Scott Fresners Book but larger. The Home Depot near me didn't have any 2 foot Strip Lights so I had to go to 48". Since they are so long I had to increase the size to 52" x 23". I put in 2 double strips and GE 40 watt Gro Bulbs. I am using screens that are 24" x 31" 230 mesh counts. I bought Ulano RLX emulsion because I have to do 100 signs and 150 T-Shirts Front and Back. Our Event is Tomorrow. I used 3M Inkjet Transparency Film. This morning I tried to expose for 5 minutes and then 5 minutes 30 seconds. I blew both screens and the entire screen washed out. I'm near Atlantic City NJ and looking for someone local that I can pay to burn my screens if I can't do them myself. ANY help would be nice. I would like to do them myself but am open to suggestions. Please Help.
I use a home depot halogen light, expose time 12 minutes, and until now it always worked, since the first try.
Try exposing a little bit longer. To me it sounds like your screen are under exposed.
Sorry but I never used an exposure unit like yours, so I can't give you a more precise answer.
Good luck.
Hope someone with more experience may give you an answer.
Thank you for your advice. I will try to expose for longer but I'm still not sure about the lightbox that I built. I called the Emulsion manufacturer and was told to expose for 10 minutes minimum but I'm still not sure.
5 minutes will probably be way to fast for almost any exposure unit. try and try til you get it right and make sure you write down the times for each mesh
Back in the 80's when I had a home-made fluorescent light table, I used GE Chroma 50 bulbs, they were about 8 inches from the glass, and exposure times were 15-20 minutes, depending on the mesh. Watch out for your detail closing in, as fluo. bulbs cause light-scatter & undercut the stencil from all directions.
Try a step wedge. It will help you. Do a search for step wedge. Also there is a video about exposing on youtube.
I burn with a 500w MH lite at 6mins with 156mesh. The light sorce is about2 feet away from the glass. the glass is 5mm thick.
All these thing take effect to your exposure time.
Light: type, watts, distance
glass: thickness, clearity
emulsion: type, quality
mesh: 100mesh = more emulsion=longer burning time VS. 300mesh= less emulsion=shorter burn time
Good luck.
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I built a Screen Exposer Unit that is in Scott Fresners Book but larger.
The Home Depot near me didn't have any 2 foot Strip Lights so I had to go to 48".
..... I put in 2 double strips and GE 40 watt Gro Bulbs.
I am using screens that are 24" x 31" 230 mesh counts.
I bought Ulano RLX emulsion because I have to do 100 signs and 150 T-Shirts Front and Back.
Our Event is Tomorrow. I used 3M Inkjet Transparency Film.
This morning I tried to expose for 5 minutes and then 5 minutes 30 seconds.
I blew both screens and the entire screen washed out.
I'm near Atlantic City NJ and looking for someone local that I can pay to burn my screens if I can't do them myself.
I feel bad for David having to resurrect his old school screen training because he couldn't find anybody near Atlantic City to make his signs and shirts.
Quote:
Originally Posted by DavidGNJ
I called the Emulsion manufacturer and was told to expose for 10 minutes minimum but I'm still not sure.
"I'm still not sure".
I'm sure that the guy at the emulsion manufacturer was sure.
The Technical Data Sheet for RLX states that suggested initial exposure with 40 watt 'unfiltered black light' is 7.5 minutes on 305 mesh. For plant-light, filtered black light, and “daylight” tubes, use double the time at least = 15 minutes. Tech Data Menu USA of Screen Making Products
Ulano also has several emulsions that expose faster than RLX, but Dave was in panic mode because of his deadline.
Emulsion is easy. If it washes out, it wasn't exposed to enough UV-A energy to cross link the sensitizer. If it doesn't dissolve and rinse down the drain - it did cross link, just like it is supposed to!
Everyone. Yes, everyone, should buy a .5" x 5" Stouffer 21 Step Gray Scale (US$6.00 to US$15.00). and simulate 21 different exposures with one test. The MINIMUM exposure for a stable, durable stencil is a solid step 7. Step 8 will be more durable, etc. Once you have found the Step 7, you can adjust your exposure to meet other needs until you find the threshold where your fine lines are choking and don't allow ink to transfer through the mesh.
When I become King, I will pass a Screen Making Law requiring people to show a 21 Step positive before you can buy emulsion.
I don't understand how writing "I use a home depot halogen light", will help David, because he already build an exposure unit, and has a deadline. If you do use a quartz halogen lamp, make sure you remove the safety glass that is there to protect your eyes from dangerous UV light.
"5 minutes will probably be way to fast for almost any exposure unit", is not very rational. He only has 230 mesh and lamps designed for exposing UV sensitive screen making stencils are listed in the Tech Data Sheet at 30 to 60 seconds.
GE Chroma 50 bulbs are excellent at reproducing a full range of the visible light spectrum, but have very little UV-A output. Sales room, art room and anywhere inspection is made, is the place for them.
8 inches from your glass is double the usual distance of 4" for standard 2 lamp fluorescent fixtures.
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Last edited by RichardGreaves; May 30th, 2008 at 06:08 PM.
Reason: Death threats
I don't understand how writing "I use a home depot halogen light", will help David, because he already build an exposure unit, and has a deadline. If you do use a quartz halogen lamp, make sure you remove the safety glass that is there to protect your eyes from dangerous UV light.
Well from my position there is not much I can do but letting him know what I use, and it is a very common light that might very well be sitting in his basement.
hkoly crab man how did this project pan out? You're trying to relearn screen printing in one day. I did it in collage too but I was only going back 2 years and its still rough going on the details today. Good luck to ya! Let us know how it went.
And to add to the last two replies:
Please use us for any help you might need in the future. I know first hand that this forum helps a lot. I learned must of what I know right here.
Good luck!!
MB
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GE Chroma 50 bulbs are excellent at reproducing a full range of the visible light spectrum, but have very little UV-A output. Sales room, art room and anywhere inspection is made, is the place for them.
8 inches from your glass is double the usual distance of 4" for standard 2 lamp fluorescent fixtures.
It was a long time ago -- we're talking early 80's -- and I suppose someone at the lightbulb store told me the Chroma 50's would give more ultraviolet than a soft white bulb.
I moved my lamps away from the glass, because much closer than that, I recall having 2 over-exposed strips down the middle, and under-exposed sides. That might not have been the case if I'd been using blacklights.
There was no internet back then, and most suppliers weren't much interested in talking at length to little guys like me, so I guess I re-invented the wheel a time or two. That said, I sure was glad when we finally got a regular exposure unit with a vacuum table an a pin-light source. 4 years with a coffee table, foam rubber, plywood and a "screen rock" to weigh it all down was about enough. :-)
The quick fix is home depot for the halogen and like mr. Greaves said "don't forget to remove the glass face from the lamp". Outside of that you will need to find better bulbs for the unit you built. After you have corrected your equipment issues do the step test. I avoided the step test for quite a while thinking I had my exposure times down pat. HAH! I gave in and did the exposure test and now after correcting my "correct" exposure times I have fine line and half tone capabilities I never thought I would be able to do.
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