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When you start combining multiple inks-- and let's face it that's almost all the time--you have to consider how interactions of ink on paper are going to affect your artwork. For example, if you have small white type and a dark multicolor background, there's a potential for all that ink to sort of pile up and encroach on the type and it might deform the edges of it. Now modern presses are much more precise than in the olden days, but misregister could still cause the type to be unreadable. And the opposite is true. If you create especially small text out of multiple inks, misregister can occur and it's going to deform that text, make it look a little bit blurry.
Now your printer maybe able to provide specifications that spell out the minimum size for white text or multicolor text or fine rules and things like that, take that advice seriously. Also, there's a limit to how much ink you can pile up in one spot on a given stock. It depends on the stock. It depends on the press. If you exceed that limit, you use adherence. Ink laid down by the previous unit might get picked up in spots by the subsequent unit. This is called total ink coverage or total area coverage, TIC or TAC.
For newsprint, for example, that falls between 240% to 260%. On a sheet-fed press running coated stock, that total area coverage might be 320% to 340%. And you're thinking, wait, how you can have more than 100%? Well, here in Acrobat using Output Preview I can sort of interrogate my file. As I move my cursor around, watch the numbers that are in the Output Preview and you'll see them changing. As I hover over this area there's a rich black background, 60 cyan, 40 magenta, 40 yellow, and 100 black. See, all those numbers add up to 240% percent.
It's probably not a problem. If I hover over this image on the left, you'll see in that lens, in the darkest shadow, that adds up to 294%. So again, it depends on what press and what stock that combination determines how much ink you can pile up. But there's a great way to find areas that exceed a given specification. At the bottom of Output Preview ,if I choose the Total Area Coverage, there is a little warning color that tells me if I'm over the allowed amount. So if I'm running on a press who's maximum Total Area Coverage is 280%, all of these areas that are highlighted in green are going to present a problem on press.
What if I'm running on a sheet-fed press that can accept much higher piles of ink in the area? Well, then that's not a problem. If you examine your files in Acrobat like this, and they're just little tiny green areas, that's probably not going to be an issue. But when you have large areas showing that you've exceeded the Total Area Coverage for that press and stock combination, what can do you? You have to go back to your original image and re-separate it or modified in some way so that Total Area Coverage is not going to exceed the specifications.
Again, keep in mind your printer can tell you what those values are. One of things that can happen when you're applying ink on paper is you could have misregistration. So what does that mean? Well, that means as the individual colors are laid down, maybe they don't line up from unit to unit. Again, this is very rare. But what happens when it does happen? Well, this is bad register. You've probably seen this on the Sunday funnies in the newspaper. You can see the colors don't quite line up and you get sort of a rainbow effect around.
Now I've highly exaggerated this, and as I mentioned earlier modern presses really don't have the problems with registration that ancient presses did. But it's still something to consider. And how do you consider this when you design? If you want to make sure nothing like this ever happens, you might want to modify your design. In this case, maybe I don't need a black background. Maybe I'll just have my color type and maybe I'll make that word Design and the word At black have it all fall on a white background, then there is much less chance that anything is going to be out of register.
One of the ways you can fix misregister is by adding something called Trapping. Now trapping is not something you ought to have to do. It's something that happens at the printer. We're going to zoom in on this text. This is a spot color orange and it's against a spot color blue. So as each color is laid down, again if there's any misregister between the subsequent units of the press, you can see a little gap between the colors, and you don't want that. What trapping does is create little overlapping areas.
It's sort like a little rim around each color where the colors don't have inks in common and those little areas have a combination of the inks. So this looks really ugly at this magnification, but in real life you're really not going to see those little rims. They're much less unattractive than any white gap between the colors. So trapping is preferable to not trapping. In those little dark borders what you're going to see where the orange type hits the blue type is really a combination of 100% of the spot orange and 100% of that spot blue.
And again, if there is a little bit of leeway on the press you're never going to see that white gap. Keep in mind that you don't have to perform trapping. It's not something you have to worry about. It's something that happens at the printer. They have specialized software as part of their workflow that creates straps. We don't have to make them by hand anymore.
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