Introduction to the Offset Printing Process

If you're a graphic designer, you're undoubtedly familiar with templates and creating full color designs to run properly on an offset printing press. Once the design is complete and sent to the printer, do you ever wonder how they take your graphic file and put it on paper? Knowing how this is done can help you become a better designer.

For the uninitiated, here's a brief introduction to the printing process:

Prepress

Before your jobs get to the press, there are several things that must be done to make sure it will look its best. Busy printers have to balance a tight schedule, so they want to make sure that each project is properly prepared to avoid problems at the press. If you're having your job printed on an offset printing press, your printer will first take your digital files and make film negatives of them. These negatives will then be used to create metal plates through a process that's similar to camera film development. If you have a four color (CMYK) design, there will be four plates — one each for cyan, magenta, yellow, and black. Once the plates are made, your project is ready to be printed.

Printing

An offset press does a lot of things in a very short amount of time to properly execute high-quality printing. Sheet fed offset presses and offset web presses use similar processes, though web presses use huge rolls of paper for high-volume printing, while sheet fed presses are just that — printed sheet by sheet — and are more suitable for short- or mid-range runs (250 to 50,000).

Regardless of the paper feed type, once it is loaded on the press it passes under a series of rollers, two of which work together to put the printed impression on the paper. Before that happens, ink and water are applied to the printing plate, which itself is mounted on a roller. The ink binds to the part of the plate that contains design elements; the water is applied to the white space portion of the paper. Oil is mixed with the ink to ensure that the ink and water repel each other and there is no smearing or blotchiness on the finished product. The plate cylinder transfers, or offsets, the design onto a rubber blanket roller, which in turn transfers the design onto the paper. In four-color printing, this process is repeated three times (once for each color) before the printing is complete and the job is ready for finishing. Often, the wet paper is run through an oven to dry.

Finishing

Depending on what you are printing, you might require finishing services such as binding and cutting. After your job is off the press, it will be put on another machine such as a stitcher for stapling, gluing and other processes. Finally, it will be cut to size and packaged for shipment.

As you can see, graphic design is just one part of a very complex printing process. Each step of the process has a specifically designed benefit. Even though most offset printing presses work very much alike, the actual quality of your job depends on a number of factors, including your printer's attention to detail and press maintenance, the type of press it's printed on, the quality of the ink and paper and even the quality of your design. If you're unsure about how to find a great printer, try an industry-recognized company such as PsPrint and make sure you ask plenty of questions to make sure your designs look great on paper every time.