# Easy, foolproof method of coating screens



## MaximRecoil (May 18, 2010)

This might help some people who are new to screen printing. I'm fairly new to screen printing myself (I've been doing it for about a year now, and only as a hobby), and the hardest part for me during my first several attempts was coating the screen. On my very first try, the emulsion was on there so thick that it dripped onto the floor as it was drying. I managed to do better on subsequent tries, but it still wasn't good, i.e., it was still too thick, and that thickness was inconsistent (thicker on one end of the screen than the other). This made it hard to rinse out the stencil after exposure; the thinner parts of the emulsion would rinse out okay, but the thicker parts wouldn't, and I had quite a few stencils that were unusable, forcing me to reclaim the screen and start over.

The foolproof method I discovered is: coat the screen as usual using the thin edge side of the scoop coater, i.e., the back then the front, not worrying about technique, air bubbles, stuttering, thickness, or anything else. Then repeat the process on both sides, except, this time, angle the back of the scoop coater downward so that no new emulsion gets applied. What this does is scrape off all of the excess emulsion, leaving a perfectly thin, uniform, bubble-free coating. It will dry quickly, expose consistently, and the stencil will rinse out easily, every time. This method has never failed me.

Some people may say that this method results in too thin of a coating, and maybe that's true for some applications, but for run-of-the-mill screen printing, i.e., spot colors with a 110 mesh screen, I get good print results (I use Ulano QTX emulsion, a 500 watt halogen work light 18" above the screen, 1/4" thick glass over the Epson Stylus Photo 1400-printed film positive, and a 7-minute exposure time). Here's an example (which also happens to be my first multi-color print, which I did, painfully, on a 1-color press):


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## jeron (Jul 16, 2012)

While this might help in the short term, i would still learn to coat a screen in one pass and have it be correct. 

Typically to much emulsion when coating is the result of not enough pressure being applied while coating


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## MaximRecoil (May 18, 2010)

jeron said:


> While this might help in the short term, i would still learn to coat a screen in one pass and have it be correct.


I'll wait until I have a printing problem that can be traced to my method of coating the screen. 



> Typically to much emulsion when coating is the result of not enough pressure being applied while coating


In all cases except for my first try, I used plenty of pressure. The scoop coater was perpendicular to the screen, and the screen was perpendicular to the table. When using a given amount of pressure, you can alter the amount of emulsion that gets applied by adjusting the screen-to-table angle and/or the scoop coater-to-screen angle, but those angles aren't particularly repeatable unless you're a robot; only perpendicular (90 degrees) is repeatable due to the plastic end cap guides on the scoop coater and the flat bottom of the screen frame, and that didn't give me good results even when pressing the scoop coater as hard as I could against the screen.

The method I described above inherently gives uniform, consistent, repeatable results every time, and I've yet to encounter a downside to it.


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## jeron (Jul 16, 2012)

MaximRecoil said:


> I'll wait until I have a printing problem that can be traced to my method of coating the screen.


Ok. Keep in mind it's sometimes harder to break bad habits once it's ingrained in how you do something. 

If it were me i would continue to try and get that perfect coat every time i coated until i got it figured out. And when it doesn't work follow up with your scraping method you described, so you can still use the screen. 

But that's just my 2 cents. Good luck man.


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## MaximRecoil (May 18, 2010)

jeron said:


> If it were me i would continue to try and get that perfect coat every time i coated until i got it figured out. And when it doesn't work follow up with your scraping method you described, so you can still use the screen.


Well, the thing is, with the type of screen printing I do, I don't see anything to be gained from a thicker coat of emulsion, but I do see downsides to it, such as longer drying and exposure times. 

I did make some successful screens before discovering the scraping method (it was very hit or miss for me, due to the lack of repeatability of the angles that I mentioned before), and the prints I made with them were no better or worse than the prints from the screens I make now with the scraping method. However, they took longer to dry and 10 minutes (instead of 7) to expose.

Here's one of the screens I made (using the scraping method) for the print I posted a picture of in the OP:










The coating is perfectly uniform, as it always is with the scraping method. The only thing that anyone could say is wrong with it is that it is too thin, though I don't see how that negatively affects my prints or anything else. Why is "too thin" of a stencil supposed to be a problem anyway? I've heard/read that it's a bad thing, but I've yet to see for myself why that's true.


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## Printor (Apr 16, 2015)

You'll find that when printing opaque colors on dark shirts, thicker emulsion on the shirt side will help leave a thicker more opaque layer of ink on the shirt. You will also find that a thicker layer of emulsion on the squeegee side will let you print more shirts before your stencil falls apart due to the friction of your blade basically sanding down your emulsion thinner and thinner with every print. saving a couple minutes in the dark room can cost you much more time in flashing and printing darks, and reburning worn out screens during big runs.


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## MaximRecoil (May 18, 2010)

Printor said:


> You'll find that when printing opaque colors on dark shirts, thicker emulsion on the shirt side will help leave a thicker more opaque layer of ink on the shirt.


I've never had a problem with opacity/coverage. With dark ink on light shirts, one stroke is enough, even with a 156 mesh screen. Of course, when printing white on black I have to print, flash, print, but I believe that pretty much everyone else does too. PFP gives me perfectly opaque white on black prints:










And the same print a year later after about 50 times through the washer and dryer (not my shirt; I printed it for a friend of mine by request):












> You will also find that a thicker layer of emulsion on the squeegee side will let you print more shirts before your stencil falls apart due to the friction of your blade basically sanding down your emulsion thinner and thinner with every print.


That makes sense, but it doesn't apply to me, because, like I said in my OP, screen printing is just a hobby. I mostly print one-offs for myself, friends, and family. I've never printed more than a few shirts from any single stencil. Without actual testing I have no way of knowing for how many prints one of my stencils would last.

By the way, another advantage of my method is that it uses a lot less emulsion, and emulsion is far from free or cheap.


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## NoXid (Apr 4, 2011)

Yup! I still have emulsion drips in the bottom of my dry box from one of my first screens 

I think it comes down to how often one coats screens. In a shop doing custom orders, one is going to do it constantly, so one develops and maintains good technique and feel. But I design and print my own line, so may go a while without making _any_ new screens, so I get rusty. Scraping off excess/uneven emulsion when one does a less than perfect first attempt is a perfectly reasonable approach and a big time saver for those who don't coat screens every day, because we simply don't do it enough to get, and stay, perfect.


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## Joe.Moser (Apr 8, 2021)

I just started doing this scraping method. I feel I was doing fine before but here and there would get an air bubble or some ripples. So I have been doing a pass without tilting the scoop coater and expensing emulsion. My concern is that when I do this- it really looks like its taking off a lot of the emulsion. I actually prefer depositing less ink so that part I am cool with. My concern is that I might run into some issues when washing out the stencil.


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