Basic Screen Room Training

Basic Screen Room Training

When the turnover of employees increase things that went well all of sudden starts to skip a beat and we all know how things go from there. Even for seasoned printers and users, it is always good to go back to the basics to review and rethink any ideas.

Part One – Screen Preparation 

1. Cleaning the screen prior to De-hazing – The first step in screen preparation is to analyze the mesh for ghosts of ink that show up from a previous print run. If the mesh is new you can skip to Step 4. But if your screen has a ghost image read on. Ghosts or fabric stains are caused by ink from the last print run. The ink can get caught in the ‘creases’ of the ‘mesh knuckle’ and is usually seen when dark inks are used. Ghosts can cause pinholes or show up in a solid print area on the next job since they can interfere with the ink transfer and leave a ghost in the print.

Preventing Screen Haze: The easiest way to minimize this issue is to clean the screens immediately after the print run. This includes plastisol as well as water base, discharge, or HSA inks. Cleaning screens while the inks are still wet will prevent ink from drying in the mesh knuckle creases. This is especially true of discharge, water base and HSA inks that can air dry. Once the ink has dried you will need a haze remover to clean mesh.

Murakami’s SC-501, SC-505 and SC-507 are designed to clean the mesh well without chemically flashing the emulsion and making it hard to reclaim. Screen Openers, Acetone, MEK, and other hot solvent chemistries can lock in the emulsion and make reclaiming difficult. Murakami screen cleaners avoid locking in the emulsion which allows the reclaiming process to go easier.

For water base and discharge inks a 5 gallon bucket of warm water works well, for plastisol or other inks the cleaners above work well, with SC-507 designed for graphic and industrial inks as well as textile inks. When companies tell me they have no time to wash the screens after a job has finished on press I point out that screen reclaiming personnel will spend 2 to 3 times as much time cleaning the dried ink compared to a worker cleaning wet screens at the press. Typically all that needs to be done is to card out the inks and wash the image area. This practice makes ghost removal in the reclaiming area an occasional job rather than needing to do it on all screens which wastes chemistry and labor.