While they're usually harmless enough, some ghosts can cause problems with your prints! Learn how to remove and prevent them.
Most of the time, reclaiming your screen printing screens is a pretty straightforward task. But occasionally you'll run into an issue that can affect your print quality if not dealt with quickly: ghosting.
Sometimes when you remove a stencil, a faint outline of the image will remain in the screen. This is called a "ghost" image (or alternately "haze"), and it can happen for a couple of different reasons. Ghosts can occur when leftover ink from a previous print run gets trapped in the nooks and crannies of your screen mesh, or when underexposed emulsion reacts with your screen cleaning chemicals. Usually ghost images are relatively harmless, aside from possibly complicating your registration a bit on your next job. However, a more serious ghost image can actually block openings in the mesh and keep ink from passing through during the print stroke, creating pinholes.
So you've noticed some troublesome ghosts plaguing your screens - what to do about them? Before you start questioning whether this screen printing job is worth eleven-five a year, let's talk about a process called "dehazing": the removal (i.e., busting) of ghost images.
Fighting Ghost Images: The Right Tools
There's a wide variety of chemicals, called haze removers,, you can use during screen reclamation to eliminate ghosting in your mesh. Haze removers can be caustic, so be careful to closely follow the instructions provided and take all recommended safety precautions to avoid harming your screens - and yourself! It's always a good idea to use chemicals in your screen printing shop that are as environmentally friendly as possible without sacrificing effectiveness, so be on the lookout for greener options.
How to Remove Ghost Images from Your Screens
Dehazing is a simple process. Just wet down your screen and apply your haze remover according to its instructions, then scrub away the stain taking care not to damage the mesh. Let the screen sit for awhile to give the haze remover a chance to work, but not too long - some haze removers can eat away at the glue holding the mesh to the screen or even the mesh itself, potentially damaging your screen beyond repair. Once the haze remover has had a few minutes to do its thing, rinse the screen. You may have to repeat the process for particularly pesky stains.
Stopping Ghost Images Before They Start
Keep in mind you don't always have to go out of your way to remove ghost images; they're really only a problem if they're negatively affecting your print quality or making your registration unnecessarily difficult. Even better than removing ghosts after they materialize, there are steps you can take to prevent them from showing up in the first place:
- Expose your emulsion properly. Underexposed emulsion is more difficult to remove from your screens and is a major cause of ghosting.
- Make sure your screens are kept at proper tension. A screen with low tension stretches more when the squeegee makes contact with it, creating more places for ink to get stuck after the print stroke.
- Don't let your ink sit too long in the screens; ink that has been sitting for long periods of time can create stains that are harder to remove.
- Take care of your mesh. Screens with worn, abraded mesh are more susceptible to trapping ink and creating a ghost image. Know when it's time to replace heavily used screens before they start to reduce your print quality.
With a little bit of effort and the right supplies, you can exorcise your ghosts easily and keep your screens in perfect shape for every print run.
Looking for some more tips on how to clean and expose your screens properly to avoid screen printing issues? Check out these blog posts:screen printing methods, screen printing pre-press, screen printing screens, screen printing supplies