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screen printing => Newbie => Topic started by: nuunlv on April 02, 2012, 08:58:57 AM
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Hello.
So i havent done it for at least year, but today when i was coating screens there was some problems with it.
Hopefully pictures(crappyphonepics) will explain problems
why this happens? i degreased screen, then dryed. emulsion was mixed 2 days earlier, but still there was some bubbles. i thought it is because of bubbles in emulsion or water didnt dry completely
when i coated screen i saw some small pins, but after some time they transformed in these beasts.
(http://s14.postimage.org/pivbuzthp/Fotoatt_ls0314.jpg)
(http://s14.postimage.org/ropmphwy9/Fotoatt_ls0315.jpg)
and then, why this happens? thicker emulsion layer in corners. does my coating technique sucks or what?
(http://s14.postimage.org/4psx6l0y5/Fotoatt_ls0318.jpg)
(http://s14.postimage.org/w1o67x5ox/Fotoatt_ls0319.jpg)
hope you will help me
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Those darker areas are from poor coating technique, but you can fix that with a little more experience, it doesn't take much. The other spots look to be from some type of contaminant still on your mesh. Maybe something drips on it after it was reclaimed. There are lot's of things that could have happened to it after it was reclaimed and before it was coated. And it's possible that it might not have been clean enough after recaim.
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It could be the screens were not dry all the way....or were not rinsed properly and there is still some dehazer on there...someone with more knowledge should tell you more.
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It looks like your pictures, when all rotated correctly, show obvious drops dripping down like something splashed onto the screen, either before or after coating, when the screens were vertical.
List, in detail, your entire cleaning, drying, coating, drying procedure, and what could have changed since the last time with no problem.
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it is definitely contamination of the mesh. Your ink degrader can cause it if there is some left in the screen. In this case it look like you might have had some on your hands when you picked up the screen and it dripped down on the mesh. It could also be that the frame was not rinsed and it dripped from it. Good rinse and clean hand will make it go away . . .
pierre
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A little water dripping of the dirty frame will cause this a lot. Get those babies clean and it should go away. You can also try to store them so that they do not drip on themselves or one another.
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+1 the contaminated/wet comments for sure--this happens to me when I'm in a hurry and the mesh is dry, but the frame is not. Handling the screens makes the drips on the frame hit the mesh, and then create a light spot where the drip was.
It used to happen when people were washing their hands in the screen room too... luckily that doesn't happen anymore. (I took the soap out :))
I've also seen similar marks on screens on the first coat when there are large bubbles in the coater--if you're having this problem and going for a thin stencil, you can coat two or three times on the inside, and then use the sharp edge of the coater to cut the emulsion off the shirt side, and pull one more on the squeegee side. It should only happen on the first screen, if this is what's going on...
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After degreasing and a good rinse you should set them aside far away from the washout booth and do not stack them on top of each other. That has help minimize those issues for me.
As far as the heavier coating of emulsion that's from not enough pressure on the coater on that side.
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The spots are most likely due to backsplash. Be sure to thoroughly clean your sink between steps.
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Heavier corners might not be your fault though, could be the screen is tensioned unevenly.
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and those won't effect your print either. my bet is the frame is dripping into the screen.
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something that could also be minimized by drying horizontally at this step as well as the standard coated screen technique
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As some others have stated The mesh may be dry but the frames may have water on them. If you are stacking your coated screens into a screen rack, it could be as simple as water dripping off the frame above to the one below as you are sliding it into the rack.
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This looks to me like you are drying the screens by standing them on edge. You should always dry wet screens horizontal with the mesh facing the floor.
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thank you all for quick responses. i will bare in mind all your suggestions and tomorrow will try to coat again.
now i washed all screens and they are drying overnight.
tomorrow i will update on progress or regress :)
thank you all
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Just to toss in my three cents that looks like water drops even though you dryed your screens water can still be in the knuckles of the mesh.. I,ve had that happen by just air drying my screens, now I put a fan on them for 30 mintues to an hour...Oh allso finger prints can cuz those problems while there still wet so don't finger your mesh LOL.
Darryl
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The spots are most likely due to backsplash. Be sure to thoroughly clean your sink between steps.
Agree
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well today everything went well. I thint it was because i didnt wash out degreaser properly.
And my coating tecnique improved also :)