screens images are jagged

[mikesorr]

We have been having trouble with some of the edges of the designs being jagged looking and not clean edges. Not sure if we are not washing out the screen long enough or it may be the emulsion or what. The artwork is clean . We are semi novice about a year in to screen printing so any help would be greatly appreciated. Thank you

[drew]

What mesh and ink are you using? If its a low mesh (under 110) and a thicker ink, you may want to up the mesh count and reduce the ink a little. I would also make sure you have very good positive contact while exposing. It could be the emulsion but I haven't had that issue with emulsion. I would also rinse the screen out with regular garden hose pressure.

[mikesorr]

What mesh and ink are you using? If its a low mesh (under 110) and a thicker ink, you may want to up the mesh count and reduce the ink a little. I would also make sure you have very good positive contact while exposing. It could be the emulsion but I haven't had that issue with emulsion. I would also rinse the screen out with regular garden hose pressure.

Thanks for responding. It is just a couple of one color jobs on 110 mesh with International Coatings Inks. It is not so much the ink as the screens when washed out the design looks jagged as if it were not washed out enough but with a garden hose and decent pressure it doesn't seem to be that. I am using a Xenon Plastolfast Direct Emulsion so not really sure what could be happening.

[drew]

I'm not familiar with that emulsion. One thing I forgot to ask is what type of exposure unit your using. If there is plenty of pressure(weight) on the screen while you're exposing the screen, it may be over or under exposing. And when your rinsing the screen out, how long does it take? If its more than 2-3 minutes, the water could be damaging the edges also. Just a few ideas. Lol.

[Catspit Productions]

Okay I’ll try to help out a bit here as this could be a technical issue. First let me start by saying that many spot color designs may look a bit jagged in the stencil on a 110 mesh but when you actually print it the edges will smooth out naturally. The knit of the garment and the bleed of the stencil will most likely print the edge crisp and it will look fine. However if you are not happy with the print then we can look at a couple of things.

What you are experiencing is known as “saw tooth” or “saw toothing.” I once considered naming Catspit Productions “Saw Tooth Screen Printing”... LOL. Any way this most often could be solved by addressing 2 things. First is the emulsion. You want to use an emulsion with good “bridging” characteristics.

Okay what does that mean? Direct emulsions are difficult to apply consistently. And because they are more than 50% water, direct emulsions can dry unevenly as the moisture evaporates. As the water evaporates out of the emulsion, it contracts and shrinks slightly. As it does, it conforms easily to the surface of the mesh and imitates its surface characteristics. Bridging characteristics describes the emulsion's ability to span or “bridge” the open spaces between mesh openings smoothly. Stencils that tend to take a longer zigzagging route around the mesh opening will create a saw-toothed edge. This means poor stencil resolution and definition. An emulsion with higher solids content will perform better in this respect. Higher solids content emulsions will also experience less contracting and shrinking during drying.

Therefore a high quality emulsion with high solid contents will have great bridging characteristics and thus excellent print resolution. Perhaps a different emulsion will work better:

http://catspitscreenprintsupply.com/emulsion/

The other thing you can look at and examine is time in the washout booth. Once again we return to this subject and we must point out that the longer you spend in the water rinsing out the stencil the more likely you may lose detail and create the saw tooth effect. By over rinsing or washing out the stencil you may inadvertently push out the emulsion where it is attempting to bridge the mesh openings. In this case we want to washout the screen quickly. Do not spend more time in the water than you need to washout the stencil cleanly. Then stop and immediately begin the drying process for the screen to go to press.

Maybe that will help you but you may want to test print the screen before you go through nay trouble to see how it prints.