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How to make better films using an inkjet.
Your RIP software has a lot less to do with the density than many users realize. Yes, it's where we control the settings for the printer such as resolution and ink flow, but it's the physical link between the film and ink that does the most to achieve proper screen exposure density. In AccuRIP Black Pearl you will access the FILE MENU>Edit Configuration to make setting changes (resolution, droplet weight, line screen, etc.).
There are many styles and brands of film even from one company. Each has different properties and different abilities. You get what you pay for. It cost more money to make a better film and the result is cleaner and sharper prints with less dot gain. Always choose the best film possible, the film is what makes a screen, we are "screen-printers". If your screens are second rate then so are your prints. There is just no other way to put it.
The emulsion layer on the film certainly helps speed the drying process and edge quality greatly reducing dot gain as well. Avoid using a film with a thin, almost "clear" appearance and never use a "non waterproof" film. Your dye ink is water based so use a proper film. The name alone "non waterproof" should tip you off that its not the best product for your needs. The slightly cloudy emulsion of the proper film does not effect the exposure process.
There are two styles: Dye and Pigment. Both make films and both need to be matched to a proper film supply (there is that focus on film again). Pigment and Dye are radically different inks so don't choose the wrong film. Some claim there are films that work "great" for both, wrong, a film works "great" for the ink it was designed for and maybe it works "ok" with the other. Buy the proper film for your inks and "test" them before you buy bulk.You want/need great results - not just good.
The industry standard is Dye ink (dye is water-based):
Dye ink is available by many suppliers and works with lower cost films, which does not mean lesser quality films. Dye ink requires a thinner emulsion layer than pigment ink.
Air dry technology:
Using dye ink means that you are dealing with an "air dry" technology. One of the reasons we like inkjets is that there is no "heat" involved in the process like with a laser printer so registration is more consistent. The films are not shrinking due to intense heat. However that also means the ink is not "fusing" as fast. It takes time for the ink to fully "cure" not just dry.
Using screen print terms, you know what happens if you print a shirt and just "dry" the ink rather then properly "cure" the ink. Well, it's the exact same thing with inkjet films.
Giving the film more time to cure before use means more water will evaporate leaving behind only the dye and UV agent. When the water is fully evaporated we call that "cured". A cured film is not only greater in density, but it's much more durable, scratch resistant and archival.
Dry ink is like pudding, it may be dry to the touch (on top), but below the surface it's unstable and easily reactivated by moisture. Press a "dry" film up against a damp emulsion screen (not fully cured) then turning on a hot exposure lamp creates a greenhouse effect. Your film will likely fall apart after its first use.
Films measured for density soon after printing will always have a lower density reading that those allowed to fully cure. A few hours is good, over night is best.
Yes, it is possible to run a screen print shop and make your films a day in advance. Yes, it involves getting other parts of the prepress process more efficient but it certainly can be done and by doing so you will always have the best films you can make. Better films make better screens and prints improving your business quality. Strive to be the best you can be. Do things right as often as possible.
Now that you know the facts you can better deal with results good and bad. At least you'll know how and why it happens.
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