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what's the point of applying more than 1 coat of emulsion?

1935 Views 5 Replies 5 Participants Last post by  vastex
I' have 2 screen, for white ink and black ink, one has 1 coat of emulsion on the shirt side of the screen and none on the other side, and the other has 1 coat on both side. the result came out the same? did i just get lucky? what's the point of coating more than once?
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The total thickness of the emulsion will determine the thickness of the ink deposit on the screen. We usually coat our 110 screens twice on the shirt side, once on the ink side in order to print a opaque white ink on dark shirts with a print/flash/print. I would suggest to at least coat each side of the screen once to totally encapsulate the mesh in emulsion. You can control the amount of ink going through the screen with a finer mesh if needed or a coarser mesh if you need more ink. Mesh count in addition to emulsion thickness will determine how much ink gets onto the screen.
The emulsion is what holds the detail to a large degree, or I should say the edge of the emulsion. You want a decent amount of emulsion on the shirt side of the screen to help avoid the jagged edge you get with lower mesh counts. That's why capillary film makes such a good print, because almost all of the emulsion is on the bottom, with a smooth face that aids in forming a tight gasket against the shirt. The coat on the ink side encapsulates the mesh, plus pushes the bulk of the emulsion to the shirt side where it's needed. I always coat my screens 2 wet coats over 2 wet coats, finishing on the ink side. Also dry your screens shirt-side down, again to bring the bulk of the emulsion to the shirt side.
You want to start on the shirt side and give it at at 2 or 3 coats to push the emulsion through the screen mesh. If you flip it over, it should look almost like jelly. The number of coats on the ink side is where you get your stencil thickness. You can coat the shirt side 5 times but if you only coat the ink side once, you will still have a thin coat. We recommend coating the ink side twice and you should have a good thickness and it will hold better detail.
Good info--just have to play devils advocate a little bit though--when you're using low meshes, it's quite possible you'll be coating a massive amount of emulsion 2/2 or 2/3 with the round edge of the scoopcoater (which you should be using for your base coat) If you're coating a 230 or a 305, you may have less emulsion than you want with a 2/2 coat--so your mesh and it's tension are a huge variable in the thickness of your stencil (or dried layer of emulsion)

Remember as well, if you have a weak light source and a diazo or dual cure emulsion, you may not be able to properly expose even a 2/2 or 2/3 coated lower mesh screen.
Good call ScreenFoo. There is really no set number of coats because the are a lot of variables. Even using different sides of the scoop coater because on some of them, one side is more rounded than the other to lay down a thicker coat
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