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screen printing => Screen Making => Topic started by: 3Deep on November 27, 2012, 12:50:02 PM
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You would think I would this this, but I don't in a way, coating a screen to get a nice gasket for printing halftones. Here is what I do which I don't think works like I think it should, I coat the screen print side first twice then the squeege side once wet on wet...I know by doing this I push the emulsion back to the print side giving the back a thicker print side, or should I coat one/one then let it dry some and then coat the print side again?
Darryl
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I have never had luck coating after the first coat is dry. Wet on wet seems to build thickness much easier using the glisten method.
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we do the same as you and have super thick stencils (20% on 300's and 50% on 110's) that produce pretty good prints.
the dry coating is to reduce the roughness of the stencil as it is pretty hard to build anything up that way.
pierre
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Here is some good info for you Darryl.
http://www.kiwo.com/Articles/Screen%20Coating%20Techniques.pdf (http://www.kiwo.com/Articles/Screen%20Coating%20Techniques.pdf)
And this
http://www.theshirtboard.com/index.php?topic=2621.0 (http://www.theshirtboard.com/index.php?topic=2621.0)
and one more
http://www.contractdesign.com/impressions/images/TechTipsNL_Apr2012JERZEES_v3_Inter.pdf (http://www.contractdesign.com/impressions/images/TechTipsNL_Apr2012JERZEES_v3_Inter.pdf)
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Darryl, don't focus on doing a certain number of coats on one side and the other. Use the glisten method, always coat the squeegee side last like you are doing, and I wouldn't worry about doing "face coats" or coating after the screen is dried. Each mesh count is different and may require more or less coats on the shirt side of the screen to get the squeegee side to "glisten" or be encapsulated by the emulsion. Then based on how thick you want your stencil to be, coat the squeegee side one time for a 15-20% EOMR and each additional coat on the squeegee side will give you 10-30 microns additional stencil thickness (typically, but everyone is different), depending on your personal coating technique. Emulsions are all different and will require different numbers of coats to glisten so just make sure you pay attention to the method and not so much coating a certain number of times.
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I think drying the screen with the print side down is very important .
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Theys Jblue I knew it was talked about on here at one time, you can read an article all you want but real world comes from people that do it everyday, I 'll check Doug out though.
Thanks for the links
Darryl
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I know one of the biggest problems I have is being consistent on my coating, and I can really tell once I set up to print, some screens are dead on and print like a dream other times I could just beat my head aganist a wall. This brings me to this question would a auto coater be idea? maybe Action needs to work on a manual coater that would give us more consistency from screen to screen with EOM.
DArryl
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There is a reason you can find used auto coaters for pretty cheap. You just need to figure out your style and stick with it. Not everyone is a good screen coater. Do like Alan suggested it will get you in the ball park. Although for halftone hi detail printing I would try a face coat to fill in the highs and lows. You will have to test and see how many you have to do for a face coat but it does make a difference in dot quality.
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Like this? This unit is 12 ys old and uses a hydraulic shock available at any auto parts store. It is designed for two handed coating. (I really frown on the one hand though some have mastered it). Drawing up plans to swivel it with an air operated foot pedal.
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Man I gotta slow down when posting
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Cool little setup!
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I think drying the screen with the print side down is very important .
That's what I beleived for years. For my shop it turned out to be wrong. We have two drying cabinets. One horizontal, one vertical- originally planned for reclaimed screens. When you compare EOM and printed ink thickness you cannot tell the difference. I have to add that vertical cabinet is extremly efficient in drying emulsion.
Boris
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we used to dry all of ours vertical and I really didn't notice an improvement. I find the horizontal cabinets to be more efficient though
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I guess it depends on the topic at hand... EOM.
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I think drying the screen with the print side down is very important .
That's what I beleived for years. For my shop it turned out to be wrong. We have two drying cabinets. One horizontal, one vertical- originally planned for reclaimed screens. When you compare EOM and printed ink thickness you cannot tell the difference. I have to add that vertical cabinet is extremly efficient in drying emulsion.
Boris
I have never tested this but I can agree with you on this. Here in Arizona the squeegee side of the screen will dry really fast. If letting the screen set horizontal even has a chance to help it has to be done in the first 5 to 10 mins. You take that and the high mess we all use I don't think the emulsion even has a chance to migrate through the mess. I think I will do a test. I am going to take a 155 mesh screen and pour some emulsion on top of the mesh. I bet the emulsion will not even go through the screen. Stand by.
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Ok so I took a 155 screen and poured a small about of emulsion on top. About a 3 table spoons. I did this with a room temp emulsion and a refrigerated one. In the first min the room temp did penetrate the mesh. The refrigerated version did not. After 5 mins the room temp was dripping from the bottom of the screen on to the table. The refrigerated one was still not penetrating the mess. After about ten mins the refrigerated one did penetrate the mesh in one area were the emulsion was the thickest on top. At 10 mins both emulsions started to harden on the edges.
This test is not real world since you would never have that much emulsion on the top of a screen It was a good 1/8th thick or more on top of the mesh. The added emulsion gives alot more driving force then you would have from a scraped smooth squeegee side. I was surprised the thinner viscosity room temp emulsion went through the mesh so fast. But as I said earlier this was a ridiculous about of emulsion on top of the mesh. Even with the thick of a deposit of emulsion the edges were still hardening in less than 10 mins. This does not prove anything but it does shop you need a thick deposit of low viscosity emulsion to even have a chance to have much if any migration. I will think of a few other tests to do but it would take a major finding to change anything I am currently doing.
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I think drying the screen with the print side down is very important .
That's what I beleived for years. For my shop it turned out to be wrong. We have two drying cabinets. One horizontal, one vertical- originally planned for reclaimed screens. When you compare EOM and printed ink thickness you cannot tell the difference. I have to add that vertical cabinet is extremly efficient in drying emulsion.
Boris
I guess that would depend on the viscosity of the emulsion you are using. I know that for us on thicker stencils I can notice if the screen was not laying flat as the emulsion shifts to the lower side before setting in. I can see where on a thin stencil it might snot shift as much.
pierre
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Pierre please explain the term "snot shift" it is new to me
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Its not that the emulsion is moving to the shirt side. You dry screens shirt side down so that the emulsion does not move to the squeegee side during the drying time. When you do your final coat on the squeegee side your driving all the emulsion to the shirt side. There is very little emulsion on the squeegee side after that last squeegee side coat.
Taking an EOM measurement does not tell you where the emulsion is. Its just a measurement of overall thickness of the mesh with emulsion applied. We could way over think this but the only real measurement is if the screen prints the way you need it to. If it works drying them vertical than good. I think we all get caught up in what is the best practice. If drying them vertical makes you loose a few microns of shirt side emulsion then its not a big deal. That is unless your coating process only leaves you with a few microns of error.
I really need to stop over thinking these things it only gets in the way of making money.
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Pierre please explain the term "snot shift" it is new to me
something to do with viscosity using common terms that most can relate to! ;D
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Pierre please explain the term "snot shift" it is new to me
something to do with viscosity using common terms that most can relate to! ;D
I think your giving Pierre to much credit for a typo.
I can see where on a thin stencil it might not shift as much.
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Ummm guess I forgot to add a smiley face. Obviously I knew what he meant. But I like the term we should use it often. Actually with the abrupt weather changes down here I am actually experience some form of Snot Shift. :) theres your damn smiley face!
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Pierre please explain the term "snot shift" it is new to me
it'snot supposed to be snot! ;D
pierre
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Its not that the emulsion is moving to the shirt side. You dry screens shirt side down so that the emulsion does not move to the squeegee side during the drying time. When you do your final coat on the squeegee side your driving all the emulsion to the shirt side. There is very little emulsion on the squeegee side after that last squeegee side coat.
Taking an EOM measurement does not tell you where the emulsion is. Its just a measurement of overall thickness of the mesh with emulsion applied. We could way over think this but the only real measurement is if the screen prints the way you need it to. If it works drying them vertical than good. I think we all get caught up in what is the best practice. If drying them vertical makes you loose a few microns of shirt side emulsion then its not a big deal. That is unless your coating process only leaves you with a few microns of error.
I really need to stop over thinking these things it only gets in the way of making money.
It can be measured. My paint thickness gauge takes pin point measurements.
If you take a thick EOM screen and put it vertical when you dry it, it will definitely "shift" and be thicker towards the bottom vs the top.
Now if you are talking about print side down vs squeegee side down then I'm not sure there is a point to the discussion... if you are going to set it horizontal then just put it shirt side down and be done with it... even if it doesn't make a difference there is also no reason not to do it that way. *shrug*
Panes of glass eventually (YEARS) shift and get thin at top and thick at the bottom, so I'm a heavy deposit of emulsion will do the same.
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Panes of glass eventually (YEARS) shift and get thin at top and thick at the bottom, so I'm a heavy deposit of emulsion will do the same.
This is why I rotate my windows. ;)
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Panes of glass eventually (YEARS) shift and get thin at top and thick at the bottom, so I'm a heavy deposit of emulsion will do the same.
This is why I rotate my windows. ;)
When you tour around the region in a band named "Liquid Sand" you end up learning a lot of things you never thought you would learn. ;)