Platemaking

Platemaking is the process of creating a printing plate that can transfer an image to a substrate during printing. In modern production, platemaking most often refers to offset lithography plates, but it also covers plates used in other systems such as letterpress and flexography. The plate carries a defined image area and a non-image area; during printing, ink adheres to the image area while the non-image area remains non-printable.

Traditionally, artwork is separated into color channels and output to film positives or negatives. These films are used to expose a light-sensitive coating on a plate in a plate imager or on a lightbox. After exposure, the plate is developed in a chemical bath to remove unexposed areas, rinsed, dried, and finished (for example baked) before being mounted on a press.

In modern workflows, computer-to-plate (CtP) technology images the plate directly from digital files. Platesetters use lasers or other light sources to transfer the image to the plate. Plate chemistries vary: thermal plates use heat to render the image, while violet/blue-light plates use light exposure. Many contemporary plates are designed to be processed with minimal chemical handling or to be chem-free, reducing environmental impact.

After imaging, plates are finished and mounted on the press cylinder or mounting system, then tested with proofs to ensure proper color, density, and trapping. Platemaking remains a key link between design and production, with choices driven by press type, workflow efficiency, print quality, and environmental considerations.