During the screen-printing process, the screens themselves are the workhorse of the entire event; ink, squeegee, and garment type are merely secondary. If something goes wrong during the emulsion, burning, or printing process and the screen is compromised, your printing project may fail. Here are 5 screen problems often made by beginners, and how to avoid them.
Emulsion Will Not Apply Well
The emulsion on the screen creates the ink-resistant border for your image, so it needs to be applied thoroughly and in a smooth layer. The quality of your final artwork image depends on how well the emulsion is applied. Sometimes new silk screeners find that the emulsion will not apply well to the screen and does not go on very evenly or smoothly.
If this is happening to you, first make sure the mesh isn't too loose or that the tension is uneven. You may need to tighten it up and try again. If you are using wood for your frame, this can happen as they age. Next, check the shelf life of your emulsion. If it's past its prime, throw it out. Keep your emulsion containers refrigerated to extend their life, and keep the containers clean to prevent dried bits from falling in.
Emulsion Washes Out Of The Screen
Nothing is more frustrating than rinsing the emulsion off the screen and watching parts of your design image disappear as well. If your emulsion is washing out, there could be several reasons. Emulsion that is applied too thickly or unevenly will wash out because exposure time cannot compensate. You may have applied it properly, but did not expose it long enough. Also, make sure you let the emulsion dry thoroughly and cure in the screen before rinsing. Sometimes lights in the exposure unit get old and lose their effectiveness. Finally, you may have your water set at too high of a pressure and are simply blasting it away. Try lowering the pressure, and make sure the water is cold or lukewarm at best.
Fine Details Lost While Burning Screens
Novices often find that as they burn screens, many fine details or features on a piece of intricate artwork are lost. Frequently the light source you use to expose the screen is at the wrong angle. Your light needs to be perfectly straight, at a 90 degree angle to the screen. If you are using too weak of a light source and a long exposure, any ambient light will contaminate the exposure. Check to make sure the light is at the proper strength. Over-exposure will make those fine details wash out.
If you do not use a vacuum exposure unit, it could be that the transparency is not making good contact with the screen. As you place the transparency on the screen, make sure you weight it down or press hard to make sure a firm contact is made. Or, simply invest in a vacuum exposure unit.
Emulsion Breaks Down During Printing
When it's time to print, sometimes the ink passes completely through the wrong parts of the screen altogether. Usually this occurs because the emulsion on the screen has broken down. This happens if the emulsion is not exposed long enough, or has not been cured correctly. If this is the case, let the screen dry for at least 24 hours first.
Emulsion also breaks down during printing if you use the wrong type of ink for that emulsion. Before you coat a screen, make sure the emulsion is suited for the ink you plan to use. Your best bet is to just use a dual cure emulsion because it is suited for both plastisol and water-based inks.
Finally, if you are screening too many prints or pressing too hard on the squeegee, the emulsion will wear down and let ink pass through. Make sure you coat the screen one extra time where the squeegee meets the screen to give it a little more strength if you plan to make a large volume of prints.