What Is Trapping in Printing & Why It Matters for Packaging

When preparing artwork for print, ensuring that colors and elements align perfectly is crucial to maintaining a professional and high-quality result. One of the most important techniques used in printing, especially in offset and rotogravure processes, is trapping. Trapping compensates for slight misalignments that may occur during printing, preventing visible gaps or unwanted white spaces between colors. In this article, we’ll explore what trapping is, why it’s necessary, and how to apply it effectively.

Why Is Trapping Important?

In printing, artwork is separated into different color layers (Cyan, Magenta, Yellow, and Black for CMYK printing). When these layers are printed onto a substrate, even slight shifts in registration (alignment) can result in unsightly gaps between colors. Trapping is the process of slightly overlapping adjacent colors to ensure seamless transitions, even if minor misalignment occurs. Trapping is particularly important in offset and rotogravure printing, where high-speed presses and material variations can cause tiny shifts. Unlike digital printing, where registration accuracy is much higher, traditional printing methods require trapping to maintain design integrity.

How Does Trapping Work?

Trapping involves slightly enlarging one color area so that it overlaps another, reducing visible gaps. The amount of overlap (known as the trap width) is usually small, typically ranging from 0.02 mm to 0.1 mm, depending on factors like substrate material and printing method.

Key Trapping Methods:

1. Spread: The lighter color expands into the darker color. This method is used when one color is significantly lighter than the other, preventing the darker color from overpowering the lighter one.
2. Choke: The darker color stays the same, while the lighter color is reduced to create the trap. This method is useful for fine details and intricate designs.
3. Neutral Density Trapping: This technique takes into account the perceived darkness of colors and adjusts trapping accordingly, ensuring that neither color dominates the other.

Best Practices for Trapping in Artwork

To ensure effective trapping in your designs, consider these best practices:

• Choose the right trap width: Too much trapping can cause noticeable thickening of lines, while too little may not effectively prevent gaps.
• Use proper color order: Darker colors generally remain unchanged while lighter colors spread into them.
• Avoid unnecessary trapping: In some cases, trapping may not be needed, such as when printing on materials that don’t shrink or expand.
• Use software tools: Professional design programs like Adobe Illustrator, CorelDRAW, and InDesign have built-in trapping tools that automate the process.

Trapping in Different Printing Methods

• Offset Printing: Offset presses require precise trapping due to the high-speed transfer of ink onto paper. Even the smallest misregistration can be noticeable.
• Rotogravure Printing: Since rotogravure uses engraved cylinders, slight shifts can occur, especially in high-volume runs. Trapping ensures sharp, well-aligned designs.
• Flexographic Printing: This method often uses softer plates, which can cause ink to spread slightly. Proper trapping helps control color shifts.

For a detailed guide on trapping techniques and industry standards, check out this Adobe guide on trapping.

Final Thoughts

Trapping is a vital part of print-ready artwork preparation, ensuring colors blend smoothly and preventing unwanted gaps due to misregistration. By understanding the different types of trapping and implementing best practices, designers and print professionals can achieve precise, high-quality prints across various printing methods. Are you preparing artwork for high-quality printing? Get a free quote today and let us help you ensure your designs print flawlessly!