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Discussion Starter · #1 ·
Lately, when I go to wash out a screen after burning an image into it, it's taking so long to wash out the design, that the emulsion is starting to peel off (the emulsion that's NOT supposed to)

A guy from Ryonet told me it should take about 30 seconds to fully wash out a screen. For me, it's usually about 3 - 4 minutes using a stardard garden hose, with a nozzle thingy on it (sprays like a shower head).

Here's what I do: (please tell me what I could be doing wrong)

1) Coat both sides of the screen one time, and let dry minimum of 2 hours.

2) Expose image into screen, for 5 minutes and 30 seconds.

3) Spray the screen with water, and let it sit for about 30 seconds.

4) Then, I wash out the design, spraying down the print side of the screen, not the squeegee side. I spray with about a medium pressure, but sometimes it seems the only way to get the non-exposed emulsion out is to practically sand-blast it, which obviously destroys my halftones....

Note: I live in Texas, but the humidity hasn't been an different usual, so I don't know if that could be a problem or not.

So, where am I going wrong?:confused::confused::confused::confused:
 

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I agree with Chris, if your having a hard time washing it out, sounds like overexposure. Also once you get the exposure time dialed in, you may want to switch to a pressure washer as it will make washing out screens a whole lot easier for you.
 

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Discussion Starter · #4 ·
The screens I'm exposing are 110 and 280 mesh counts. I'm using a lightbox exposure unit I purchased from Ryonet. Screen Printing Exposure Unit, Exposure Unit Screen Printing

5 minutes & 30 seconds (exposure) has always worked for me in the past, which is why I'm confused. Should I go down to 5 minutes? 4 minutes?...

And when I'm washing out, should I be spraying down the print side?
 

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Discussion Starter · #5 ·
And something else I'm not understanding.. Why would over-exposure affect the print portion of the screen? The "print" part is what doesn't exposed to UV rays (the ink on the transparencies is blocking it out), so why would over-exposure affect it, if it's technically not being exposed?

Does that make sense?
 

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In my circumstance, if a coated screen stays unburned for over 4 or 5 days it gets stubborn. Less if the temperature is up. :)
 

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We have the same exposure unit Daniel and we usually expose for 4.5 minutes and have never had a problem since dialing in to this time frame. I'm sure everyone is a little different but you may wanna try exposing for less time.
 

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if it's over exposed light will eventually go threw your transparency ( Exposing both positive and negative). So the print wont shoot out. It will over time and pressure, but then your emulsion will start to break down. Different mesh require different exposure times, especially a 280. I would shoot if for less. I don't know what your printing but You most likely don't need 280, use 230 especially for manual printing. Some emulsion do not work well with half tone and fine mesh (detail). Also some exposure units are not good for shooting high mesh detail. But let's not worry about that. Are you washing your screens outside? sun plays a factor especially if you rinse and let set for 30 sec. I always hit my print side with water just to get it wet. If it's being fussy and wont shoot out i'll hit the print side some more. I put 2 coats on each side of my screens because it lasts longer and wont break down as easy (takes longer to shoot out). Doesn't mean you need to. Also emulsion will go bad after a while, shelf life depends on the kind you use. A sure sign of bad emulsion is you will start to get pin holes and wont shoot out properly. But I don't think that's the case for you. Also if you mesh is white shoot it for less time then yellow mesh. It take a lot of fine tuning but you'll get there.
 

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Does the emulsion start to bubble off while you are washing the screen? Also I still say using the water hose (although i've heard it works for some people) is not the best way to go. We tried the water hose at first and it never worked properly as it would start to wash of the stencil only to start bubbling the whole screen after a while. We switched to a pressure washer and it works way better. Emulsion age can be a factor like other folks have said. You may have to do an exposure test to see what is the best exposure time. You said you have washed out stuff in the past without issue though right?
 

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SystemVoid

Just my two cents to muddy the waters, I use the dual cure diazo pink emulsion and usually coat 2 and 1. I let dry overnight then I use the halogen light setup to expose and actually expose for 12.5 minutes on the 120 screens. I did get the pressure washer from Lowes and it makes life much easier. My screens wash out in less than a minute....no bubbling or peeling. by the way, I recently moved from Georgia to San Antonio and had kept some coated screens in a hot storage (PODS) for 4 months...when I pulled them out to use they worked great...maybe I got lucky? Keep us posted on what you figure out.
 

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Darn Larry, What brand did you use? If I can let a screen sit for 5 days and it goes stale, maybe I ought to try your brand. :)
 

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You should be letting your screens dry in a room with a dehumidifier and a fan if you're not already. I didn't see your mesh count but I thought someone said 280? I would try a 230 or even a 195. Coat the print side twice squeegee side once. Rotating and flipping between hits. Set flat in a drying rack or something to set them on two bricks on each side of frame. Never leaned against the wall. Make sure that your film is not "see throughish" like when your're running out of ink in a printer. That has to be solid black. (This has happened to me and drove me crazy before finally I looked at the positive and fixed the issue) At what DPI are your halftones? Are you keeping your emulsion in the correct conditions? Try a pressure washer rather than hose but practice on a few screens before you do the critical ones and adjust accordingly. Depending on your set-up, have you ever thought of Capillary Film?
 
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