Off Contact Printing
If I walk into another shop and hear the “ripping and popping” of screen lifting off the garments or tacky platens on press, I’m going to scream. We have all seen the slow motion picture of a drop of milk spreading little droplets in all directions; well ink does the same thing. It spatters when torn off the garment at high speeds. If your screen does not gently pull away from your print after the squeegee has passed over an area leaving the screen and the garment separated by the end of the print stroke then you do not have enough off contact. If you need more than a slight amount then you need tighter screens.
The tighter your screen tension is, the cleaner and brighter your prints will be. Use tight screens.
When inkjet films are sticking to the emulsion and their peeling off. How can you prevent this? First identify why it is happening and then you can make the moves to correct it.
Inkjet printers are “non photographic” processes, unlike the old days of stat cameras, imagesetters and even thermal devices. Inkjets produce films by spraying ink to a surface layer and adhering to that surface. The process is far less durable and requires a little extra handling and understanding and it will result in a film that offer repeatable use.
As with anything there is a right and wrong way to handle a situation. When we used stat cameras and imagesetters, we had to develop, then fix the films and finally dry them before use. When printing t-shirts you know the difference between dried ink and cured ink. Cured is durable, dried is not. Well, inkjet inks are the same except they are air-dried and not force dried (cured). Just like pudding, inks first get a top skin layer that seems dry to the touch, but below the surface it is still unstable. Only when the water in the ink has evaporated and only the dye residue is left behind, can it be considered “cured”. This is why it’s so important to test your prints, making sure you are not over applying ink onto your film and that the film you are using is correct for the style ink you are using (dye vs. pigment). This match is critical to your success. On that note, not all films are created equal, and some release their emulsion layer to the screens emulsion taking the ink with it. If you feel this is the case, then test another brand.
When the proper amount of ink is applied to the proper film it dries rapidly. Films should come out of a printer dry to the touch and after an hour or two they should be “fully cured”. If you can get on top of your work schedule and print films a day in advance they will not only be more durable but denser as well. That is right, they will be darker. Density rises as the water in your dye based ink evaporates leaving behind only the dye.
Here’s the why:
Water and moisture reactivate water-based components. Add some heat and pressure and you have the making for a mini disaster. Your emulsion has water in it and so does your ink. Lets say you print a film and rush it to expose a screen (never happens I know, but humor me here), lets also assume you coated your screens about an hour ago on a humid day or in the same room you wash out your screens in (again, that never happens, right?).
The emulsion on the screen is still damp, the film is not fully cured, and you press them together in the vacuum table and flip on some HOT lamps. Bam! You will expose the screen, but there is a very small chance the film will survive this process.