If you’ve ever heard a printer talk about “trap” or “trapping,” they’re not talking about catching anything. In the world of prepress, trap is a technique used to make sure your colors line up correctly on press, so you don’t end up with unwanted gaps or bare stock showing through your design.
Here’s a simple breakdown of what trapping is, why it’s important, and how you can catch mistakes before your label goes to print.
Why Do We Need Trap?
As labels move through a printing press, the stock can shift ever so slightly. If two colors are butted right up against each other, even the tiniest movement can cause them to separate, leaving a thin white line where the stock peeks through.
Trapping prevents this problem by making the colors overlap just a little. That way, even if there’s a bit of movement, your design still looks seamless.
How Trapping Works
- Light Colors Next to Each Other
For example, cyan next to yellow. In prepress, we’ll add a thin line of yellow that overlaps into the cyan. It’s nearly invisible, but it gives us a safety net. - Medium Colors
When two medium colors overlap, you may notice the trap a little more; it can appear slightly darker. Still, it’s far better than seeing bare stock. - Dark Colors
Darker combinations are the easiest. With black, traps are basically invisible, and sometimes we’ll even set black objects to overprint entirely, which makes them richer and darker.
Overprint Preview in Illustrator & Acrobat
One of the best ways to catch issues in your design is by using Overprint Preview in Illustrator.
- Go to View > Overprint Preview.
- Unlike regular Preview mode, this simulates how inks will actually interact on press.
- It gives you a more accurate view of your colors and helps spot problems early.
When proofing you can do the same thing viewing your pdfs in Acrobat or Adobe Reader.
- Go to Preferences or Settings > Page Display > Use Overprint Preview: Always.
- If your customer has this setting set they can catch problems too.
For example:
- Black type set to overprint looks great.
- But if you accidentally set white text (0% CMYK) to overprint, it won’t print at all. In Overprint Preview, you’ll see it vanish—giving you the chance to fix it before sending files to your printer. Change your overprint setting in Illustrator in Window > Attributes
The Bottom Line
Trapping may not be glamorous, but it’s essential for high-quality printing. A little overlap between colors prevents white gaps, ensures cleaner results, and saves costly reprints.
And by working in Overprint Preview mode, you can spot potential mistakes early, keeping your design production-ready.
Watch the video below to see trapping in action, with real examples of how colors overlap on press.
At Rose City Label, we sweat the details so your labels look their very best. If you’re not sure about file setup or want us to double-check your artwork, we’re always happy to help.