Use Rich Black to Stop Colors Seeping Through
I am having trouble with colours printing in an incorrect way. If I draw a yellow box, for example, and then place a black box over it the yellow behind the black box seeps through when I print. How do I stop this?
Yes, you have to be careful with that! I remember seeing a full page ad in a glossy magazine of a shirtless runner, with a giant black stripe over his, um, privates. The whole point of the advert was that he was supposed to be naked (you know, with a message something like "don't get caught without protection"). But the designer had used solid 100% black ink. The result was that you could see right through the black stripe and see that he really was wearing running shorts. The whole point of the (obviously expensive-to-run) ad was ruined due to 100% black ink.
The problem is that black ink isn't truly solid black -- it's more like charcoal gray. And worse, the [Black] color in the Swatches panel will, by default, always overprint anything under it. You can get a sense for that if you turn on View > Overprint Preview and open the Preferences dialog box, click the Appearance of Black pane, and set the On Screen pop-up menu to Display All Blacks Accurately.
There are several options for making your black box look more solid and stop the yellow from bleeding through:
- You could turn off the Overprint [Black] Swatch at 100% checkbox in that same preference pane. I do not recommend this, because you probably want some black stuff (like normal black text) to overprint.
- You could set the black frame to a tint of 99%. That would force the black to knock out instead of overprint the yellow frame. But I don't recommend that either.
- You could make a new color swatch of 100% black and apply that instead. You can even call it Black. That will knock out, even if it's 100% black, because it's not the built-in [Black] (with brackets) color.
- But the best thing to do, if you are printing in color, is to create a "rich black" -- a CMYK color swatch which is a combination of colors, such as 30% cyan, 20% magenta, 20% yellow, and 100% black. (Different people have different recipes for a good rich black.) This will give you a true "black" color on the page, full of vigor and vim, ready to overpower anything you put under it.
So... moral of the story: Don't get caught exposed and without protection! Use Rich Black!