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screen printing => Screen Making => Topic started by: Dottonedan on January 26, 2016, 09:13:32 PM
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I want to get into discussing the coating technique and why you use that. Each emulsion and mesh supplier will give you the optimum EOM for what you want to achieve but to do that, you need a EOM meter. Not many actually buy these gadgets needed but you should. Once you do, you will figure out why.
Without one, the best you can do is to practice the glistening technique mentioned on the HOME page articles.
We always talk about the desired "one hit white" but how is that even possible? Does that mean you would never need a top white? No. What that means is that you don't have to hit your underbase 2 times or Print Flash Print Flash then top colors.
When you coat your screen and you see knuckles like the image below in your stencil, it's not enough. Can you get by? Yes, but in truth, it's not even average. It's sub par for image quality and print production efficiency. Here's where you step over a dollar to save a dime. Thicker emulsion provides a higher wall of image edge. Crisp and clean ink deposits and faster production.
Low EOM promotes poor edge definition, enables the ink to squash out and leave blurred edges as well as leaves those saw toothed jagged edges on angles and curved type in addition to requiring more print strokes, slower stroke, excessive angles to cover properly.
Lets see where you stack up with everyone else.
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Dan, you should look at 2ILL's youtube on coating. Every bit as informative as his "How to print a t shirt"
(sorry, couldn't resist)
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I'd love to know what the best EOM meter is for practical use, as well as what the best results should be. I'd like to get one this year.
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Easily half of my work is on 160's and low and behold, my usual technique was left off of your choices.
Though I am not locked into numbers since I use the glisten method, it most often works out to 2/1 with the round edge, with a high solids emulsions.
Actually pretty much the same down to 125's and 140's, and the occasional 110's
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Lets assume the heaviest deposit or intended coverage is on the shirt side. Typically the last stroke is on the squeegee side pushing the emulsion out to the shirt side right?
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or you could be like us and for whatever reason we are achieving 20% EOM on the shirt side with 1 round-edge coat on the shirt side, nothing on the squeegee side.
took us forever to figure that one out.
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Lets assume the heaviest deposit or intended coverage is on the shirt side. Typically the last stroke is on the squeegee side pushing the emulsion out to the shirt side right?
Yep, exactly. With the glisten method, one makes as many strokes as needed on the shirt side, to see a sheen (glisten) on the squeegee side, then one stroke there to push it back to where it belongs.
So, for me, and my round edge, on these lower meshes, it's usually 2 and 1.
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or you could be like us and for whatever reason we are achieving 20% EOM on the shirt side with 1 round-edge coat on the shirt side, nothing on the squeegee side.
took us forever to figure that one out.
I've seen one shop do that. It was a mega shop So, it's true that one method doesn't fit all, but it all depends on what you are trying to achieve and why.
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What is the best gauge for the money??
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Monster Max scoop coater. 19" W. 23x31 Shurelock Frames. Murakami Panels.
Saati PHU:
150S Mesh is close to 50% eom - I know its high, but I get amazing white bases.
150/180 Mesh 25%-30% eom. No issues with dot/edge resolution or dot gain/edge detail when printing.
Those are all 1x2 coat. There is only a sharp side to the coater.
110 and lower I do 2x2 at least.
The PHU is kinda like Honey, difficult to find a good coat technique since it reacts differently that most emulsions.
Saati Graphic HU:
225S Approx 25% eom We max out at 60LPI, holds dots and prints like a champ.
225/270/330 - 20% or so
1x1 coat slow.
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For low mesh (125 and under) we have found 2/2 sharp, last swipe on squeegee side is ample.
Round will of course deposit more, but enough emulsion "wicks" out of trough with sharp side,
preventing possible drips, etc. Believe it or not a 25 year old AWT coater. Protect them there edges. :)
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or you could be like us and for whatever reason we are achieving 20% EOM on the shirt side with 1 round-edge coat on the shirt side, nothing on the squeegee side.
took us forever to figure that one out.
I've seen one shop do that. It was a mega shop So, it's true that one method doesn't fit all, but it all depends on what you are trying to achieve and why.
I was being tongue in cheek.. having such a high build of emulsion was causing us difficulties in other areas.. and no matter what we did we couldn't figure out how to get it lower... 1x1 sharp was around 6%, and then would build almost immediately into the 35-40% range with a 1x2...
Actually tho, interesting to see that Colin is getting the same results as I am with the same emulsion... if I do a 1x1 round, I get around 50% EOM.
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we just bought a used Saati Gauge.
Can someone run down the basics of how to measure the EOM?
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Saati PHU:
150S Mesh is close to 50% eom - I know its high, but I get amazing white bases.
The PHU is kinda like Honey, difficult to find a good coat technique since it reacts differently that most emulsions.
Hey Colin, What exposure unit are you using?
We have a 850w MH unit and been using PHU also, but we seem to have a tougher time on our S-mesh getting it to crosslink completely through when we coat them thicker. I don't have an EOM gauge yet, but just going on our trials and experience.
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Hey Colin, What exposure unit are you using?
We have a 850w MH unit and been using PHU also, but we seem to have a tougher time on our S-mesh getting it to crosslink completely through when we coat them thicker. I don't have an EOM gauge yet, but just going on our trials and experience.
are you sure it's a crosslinking issue? What's your symptoms?
if it's edge breakdown/squeegee wear, it's could be an adhesion issue...
once we started using a mesh abrader (Saati DirectPrep-1) before putting the screen into production the first time (yes I know this flys against all current advice)... all of our edge breakdown issues went away.
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same with us.
One thing i Did just find out about though, is that there is a possibility with HSA inks that the PHU and the PHU2 might be absorbing moisture of the ink, causing it to dry out faster.
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mostly S mesh with SP-1400 here, with some 280 and 110 standard mesh, and a handful of lower meshes. Monster max coater.
On everything but the 280 I use 1:1 with a relatively slow stroke. 110 and all of the S mesh has a perfect glisten with just the one stroke. Cleanup stroke on squeegee side mostly for insurance with possible air bubbles/streaks, and to build the eom a bit. Don't have a gauge, but I think it is likely higher than many shops. I can feel the edge of the stencil a bit on every screen after washout. 280 takes 2:1 for glisten etc.
every once in a while I will do a 2:1 on the 110/135S if I am going for a thick ink deposit on a transfer, or weird fabric or one hit whites on a back that is mostly all small text etc. On the lower specialty meshes I use a different emulsion and those I basically go as thick as possible without drips and irregularities. I don't have those dialed in at all because of how rare they are used.
Just an aside, what is the logic behind multiple coats on the squeegee side? I have never seen any benefit to this unless you are compensating for the emulsion not penetrating the mesh to get the glisten you want, or maybe its needed for a really high eom with a super thick emulsion?
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same with us.
One thing i Did just find out about though, is that there is a possibility with HSA inks that the PHU and the PHU2 might be absorbing moisture of the ink, causing it to dry out faster.
We were experiencing this when we weren't post exposing long enough.
I sent a quart of our hsa to saati and they said no problems found.
But I do agree we had something going on.
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Hey Colin, What exposure unit are you using?
We have a 850w MH unit and been using PHU also, but we seem to have a tougher time on our S-mesh getting it to crosslink completely through when we coat them thicker. I don't have an EOM gauge yet, but just going on our trials and experience.
are you sure it's a crosslinking issue? What's your symptoms?
if it's edge breakdown/squeegee wear, it's could be an adhesion issue...
once we started using a mesh abrader (Saati DirectPrep-1) before putting the screen into production the first time (yes I know this flys against all current advice)... all of our edge breakdown issues went away.
This will totally derail this thread... I'm going to start a new thread on this... I've been meaning to anyways.
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With a full coater, when coating 81 SDE through 110S, first one coat on the substrate side, then one on squeegee side, I controlled pressure and speed to get the result I wanted. As the coater drained down, I might add a second coat on the squeegee side, but that was my hint to refill the coater. I've always preferred the sharp edge...
Steve
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Interestingly enough EOM recommendations do not take ink rheology and foundation into account. HSA, Acrylic, and waterbase products may have different requirements for instance
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Or detail requirements, for that matter.
We're lucky though--the substrate is rather forgiving in most textile printing... :)
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I use an AWT with the sharp edge, 2 over 2 (wet on wet) for 305 all the way down to 110, S-Mesh or T-Mesh. For 83, 60, 40 (Mostly all T-mesh in this range) I do one over one. I always start on the shirt side and end up on the squeegee side.
I coat pretty quickly, and don't get along very well with letting anything touch the mesh except the edge. Touching the shoulders as many do doesn't work for me.
I'm NO EXPERT. But that's what I'm currently doing at this point.
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Maff:
Start your new thread about exposures etc and I will chime in there.
When exposing S mesh I have definitely seen emulsion behave differently and the details should be put into that thread.