# How many coats of emulsion?



## DeuceDime (Apr 1, 2008)

What are the benefits to emulsion-coating my screens more than once on each side?

Is this necessary in some instances?

How do multiple-coated screens effect exposure times?


Just curious.


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## IDINDUSTRIES (Sep 28, 2007)

I usually coat my screens 1/1 and we have printed hundred thousands of shirts...


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## DeuceDime (Apr 1, 2008)

Yeah, I've printed a lot of shirts also using 1/1, but I've seen videos and heard talk about how double or triple coating is helpful in certain instances. I'm skeptical as to whether it's necessary, but I thought I'd gather the general consensus on the matter.

Thanks for the feedback.


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## James R (May 3, 2008)

I'm going to chime in here my first post, even though I don't print Tees. The benefit of more coats is mesh over emulsion the Rz value, rougher your stencil the more llikely hood of bleed. The emulsion shrinks back into the knuckles of the mesh when dry causing this, but it too many coats can give you problems also too smooth causing static and sticking to the substrate. I've been printing 4 color process on flat stock for 12 years and we coated 2 over 2 wet on wet with fantastic results on 380/34 mesh.
But it all boils down to this is what you are doing working? Any problems? Like everyones granfather said "if ain't broke don't fix it" But if you want experiment have at it. You can get multiple coatings on one screen coat once rotate coat half way up rotate and repeat just coat once or twice full on the squeege side.

Jim


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## ftembroidery (Nov 25, 2006)

Obviously the more coats of emulsion, the longer it will take to expose. I was at the ISS show in Long Beach in January and the guys from Murakami (I use their TXR emulsion) were showing me a screen they did with 1 coat on the squeegie side and 4 coats on the shirt side. Once it was properly exposed (read: do a step wedge test to determine exposure time) they blew out the stencil with a pressure washer. Now admittedly, it was a spot color design with no half-tones, but it was sharp and clean. It looked like it had been knife-cut. The thickness of the stencil on the shirt side creates a "mold" effect containing a single, "tall" or thick layer of ink on the shirt that sits up quite proudly on the shirt. The multiple layers of emulsion were also glass smooth against the shirt which makes for a good "gasket" effect to contain and constrain the ink as it's sheared off by the squeegie. I can see that making for good "white ink on black shirts in only one pass" type of printing.


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## fdsales (Jul 1, 2007)

Yes, agree w/ ftembroidery. Usually we coat 1/1 for 98% of jobs, but if we have a job where it's going to be white or gold on dark shirts w/ text or very simple design, and we want a heavy deposit of ink, then we'll coat 2 or 3 times on the shirt side. As the previous poster explained, this allows more ink to lay down onto the shirt, giving a very heavy "hand", but sometimes that what the customer wants. Also, your exposure time increases, but if there's no halftones involved, then a bit over exposed is usually better.


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## rammstine911 (Mar 12, 2011)

Do you coat the screen while wet if your doing a double coat or coat it again when dry?


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## ManiacWrk (Mar 13, 2011)

rammstine911 said:


> Do you coat the screen while wet if your doing a double coat or coat it again when dry?


Coat again after screen is dry


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## alan802 (Mar 24, 2008)

rammstine911 said:


> Do you coat the screen while wet if your doing a double coat or coat it again when dry?


No, face coating or coating a screen after it's dry is not that beneficial and is unnecessary for 99% of the jobs you'll do on tees. To build a sufficient stencil, or emulsion over mesh ratio, coat the screen wet on wet. For example, a 156 mesh screen with a photopolymer emulsion with 44% solids content would need 2 coats on the shirt side, then 2 more coats on the squeegee side with the round edge of the scoop coater, all wet on wet. That will give you a sufficient emulsion over mesh ratio to print just about anything on a tee shirt. Most shops don't put enough emulsion on the screen and print with stencils that are too thin, which I don't have a problem with, but it does affect the quality of the ink deposit, thickness of course and edge definition to be specific.

I've tried face coating (coating an already coated dry screen) and found it to be a collosal waste of time, and not to mention very messy and difficult. Face coating won't really make your stencil thicker (only slightly), it will only smooth out any peaks and valleys you created with your original coat job.


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## nikicampbell (Nov 6, 2009)

alan802 said:


> No, face coating or coating a screen after it's dry is not that beneficial and is unnecessary for 99% of the jobs you'll do on tees. To build a sufficient stencil, or emulsion over mesh ratio, coat the screen wet on wet. For example, a 156 mesh screen with a photopolymer emulsion with 44% solids content would need 2 coats on the shirt side, then 2 more coats on the squeegee side with the round edge of the scoop coater, all wet on wet. That will give you a sufficient emulsion over mesh ratio to print just about anything on a tee shirt. Most shops don't put enough emulsion on the screen and print with stencils that are too thin, which I don't have a problem with, but it does affect the quality of the ink deposit, thickness of course and edge definition to be specific.
> 
> I've tried face coating (coating an already coated dry screen) and found it to be a collosal waste of time, and not to mention very messy and difficult. Face coating won't really make your stencil thicker (only slightly), it will only smooth out any peaks and valleys you created with your original coat job.


I'm trying to get a thicker stencil (doing sweatshirts - so I really want to lay the ink down on the first pass to eliminate the fuzz raising off the garment when I lift the screen) - when you are speaking 2/2 - are you doing this: 

print side, coat > rotate 180 > coat 
ink side, coat > rotate 180 > coat

are you using the round edge for all those passes?

thanks!


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## gerryppg (Jan 29, 2010)

nikicampbell said:


> I'm trying to get a thicker stencil (doing sweatshirts - so I really want to lay the ink down on the first pass to eliminate the fuzz raising off the garment when I lift the screen) - when you are speaking 2/2 - are you doing this:
> 
> print side, coat > rotate 180 > coat
> ink side, coat > rotate 180 > coat
> ...


 You could do it this way:

I have found on a 156 mesh mesh 3 coats wet on wet on the shirt side, the emulsion should have a nice wet gloss to it on the squeegee side and then do 1 coat on the squeegee side and that will give you a nice stencil to print just about anything.


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## ScreenFoo (Aug 9, 2011)

+1 Gerry, although depending on your mesh count vs. thread diameter vs. tension, the numbers may change.

A popular way to do this is to coat the print side enough times to get the gloss he's talking about, and then put one or two strokes on the squeegee side.

And yes, use the round edge to build up base coats. (I know the fresner book says the sharp side, I'd love to find out why)


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## nikicampbell (Nov 6, 2009)

ScreenFoo said:


> +1 Gerry, although depending on your mesh count vs. thread diameter vs. tension, the numbers may change.
> 
> A popular way to do this is to coat the print side enough times to get the gloss he's talking about, and then put one or two strokes on the squeegee side.
> 
> And yes, use the round edge to build up base coats. (I know the fresner book says the sharp side, I'd love to find out why)


okay - thanks! But I'm supposing that it will vastly increase my exposure time - do you think 2x what I do for 1/1 (I used the sharp side for the 1/1) - I have the exposure calculator but wondering generally what would be a good starting point.

Thank you - thank you - thank you


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## thutch15 (Sep 8, 2008)

nikicampbell said:


> print side, coat > rotate 180 > coat
> ink side, coat > rotate 180 > coat


Niki this is the process I follow... I use the sharp side of the squeegee.


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## nikicampbell (Nov 6, 2009)

thutch15 said:


> Niki this is the process I follow... I use the sharp side of the squeegee.


so in your opinion - do you think I should start by doubling my 1/1 exposure time? is that a good starting point?


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## thutch15 (Sep 8, 2008)

nikicampbell said:


> so in your opinion - do you think I should start by doubling my 1/1 exposure time? is that a good starting point?


Not on wet coat... If you were letting if dry then putting a second coat on you would be looking a around double time. I do two coats wet on wet.


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## nikicampbell (Nov 6, 2009)

thutch15 said:


> Not on wet coat... If you were letting if dry then putting a second coat on you would be looking a around double time. I do two coats wet on wet.


should Increase time a bit?


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## ScreenFoo (Aug 9, 2011)

An exposure calculator is far more efficient and accurate than conjecture for finding the ideal exposure time for your application. If you don't have one, I'd start around 25-50% higher exposure time. If you have blocky spot color screens to do, they're the easiest to overburn and still use, if you have good positives.

Thutch: According to people with more cool toys than me, a face coat with the sharp side will add literally like a micron to the overall thickness of the stencil.... It seems to me to be easier to build up a very thick stencil initially wet on wet. (If that's what you're going for) Do you have a non-standard technique that adds a large amount of emulsion to a once-coated stencil evenly that you'd like to share? Sounds interesting.


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## thutch15 (Sep 8, 2008)

ScreenFoo said:


> Thutch: According to people with more cool toys than me, a face coat with the sharp side will add literally like a micron to the overall thickness of the stencil.... It seems to me to be easier to build up a very thick stencil initially wet on wet. (If that's what you're going for) Do you have a non-standard technique that adds a large amount of emulsion to a once-coated stencil evenly that you'd like to share? Sounds interesting.


If I want to make a screen with a thick coat I just use the round side... same method two passes on the shirt side followed by two passes on the ink side. I just upgraded scoop coaters and the new one put down a lot more emulsion, so I have not dialed in my time on this method. 

As for coating after it had dried, I just coat with the round side on only the shirt side. Sorry I don't have any thickness data to share, but with round side wet and round side after it has dried... it equals a thick shirt side emulsion layer.


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## ScreenFoo (Aug 9, 2011)

I gotcha-- I played around with face coating with the round edge, (seemed like it would be much more convenient,) but in my experience the center ends up unacceptably thicker than the sides, as well as being extremely dependent on the speed that you coat, and the tension of the screen.


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## nikicampbell (Nov 6, 2009)

okay - this is a big- BIG thanks to both @ScreenFoo and @thutch15 for moving me towards victory! I have finally gotten my required thicker stencil. Method (for future references):

print side: coat w/sharp edge >> rotate 180 >> coat w/rounded edge >> rotate 180 >> coat w/rounded edge (got the glisten)

ink side: 1 coat w/rounded edge >> into the cabinet

exposure: 1.5x regular 1/1 exposure
21 step result: #8 basically (not 100%) washed out

....now I wait until it is dry and then tackle the project at hand. Thank you so much!


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## Alan Buffington (Oct 27, 2010)

OK, we need some more information to help out here.

What works for one person may not work for another, from 1:1 coating to 3:3 coating a lot depends on your equipment, emulsion, art, film, and coating technique. Here are the things to think about when coating the emulsion.

1. Your exposure unit's strength needs to be evaluated. If you are using fluo tubes, weak shop lamps, 1 to 1.25k units, then you need less emulsion to shoot a decent screen. Quite often these systems have a hard time penetrating an optimum coating, or a good RZ value. Also you are better off with a less viscous emulsion that doesn't build up too thick a stencil since the light has little amplitude to expose all the way to the inside of the screen. Long exposure times needed on lower wattage systems undercut art details. The longer the exposure the easier it is to undercut halftones. If you use vellum or weak black ink jet positives this is also true. Coat 1:1 on coarse mesh below 200 using the dull side, if you still have problems getting the emulsion to expose completely go to a 1:2 sharp edge of coater. Use a lower viscosity emulsion, 4000 CPS is maximum viscosity. On mesh above 200 use 1:2 sharp where the first is on the print side, the next two are on the squeegee side, rotate 180 degrees on the inside coat to prevent pinholes. (Some can get their systems to work with more coats, longer exposures etc, it can be done, this is just a ball park to get your system to expose emulsion consistently.)

2. If you have 1.5kw to 5 kw systems move up to a higher viscosity emulsion in the 8000 centipode range. Here too you can go with 1:1 dull edge below 200 and 1:2 sharp above 200 mesh. Exposure times will be much shorter with 5-7kw lights. SBQ pure photopolymer will shoot in 45-60 seconds or less whereas this could be a 12-18 minute exposure on fluo tube systems regardless of what the manufacturer claims, trust me I do this all day long. 

3. EOM (emulsion over mesh) is art dependent. UV printers of graphics use 3-4% for fine halftones, Simulated process is around 4-7%, WB and Discharge 7-12%, and high density can be 400-600% EOM. One size fits all coating techniques work typically for high wattage 5kw systems which has excellent light strength, short exposure times, and can image any detail typically. Thick high density screens can be almost impossible without strong light. You have to bake it with the right light to get good results.

The product Photocure TXR was described above to make thick high density stencils, the correct product is Aquasol HS from Murakami that can be coated 2:4 wet onto wet to make a 300-400 micron(or thicker) thick film screen.

The glass reflection technique described above is valid, you should see the bottom of the screen reflect like glass when coated well, however it can also be too much for weak systems as described above. 

A step test is your only way of knowing your coating and exposure time for your system. I would start with details. If you can't get details to wash out, reduce the number of coats or switch to the sharp side. Once you get details in the 10% tonal range or sharp 8 point copyright type washing out note the coating technique. Not all mesh uses the same technique. Typically mesh below 200 uses one technique, mesh above 200 another. 

So start with coating 1:1 dull edge below 200, 1:2 sharp above 200, run a step test, (you can find out how to do one at murakami screen dot com on their home page.). Then realize you need to do a step test for most screen counts you use. You should be using a scoop coater, one with end caps that should be used to keep the coater angle constant. Squeegees _should not_ be used for coating if you want consistent screens with good details and minimal breakdown, only use if you have no choice.

You can email with specific questions on coating and exposing if you wish.

Alan Buffington
[email protected]


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## ScreenFoo (Aug 9, 2011)

Interesting info on the viscosity vs. exposure light source...

So if I want my emulsion thicker I can just throw it in the fridge, right?


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