Offset printing is a widely used commercial printing technique that produces consistent and high-quality printed materials. It’s often used for large production runs, typically 1,000 copies or more. This method is also popular for gang or combo runs, where similar jobs from multiple customers are printed together to reduce costs.
How Offset Printing Works
Offset printing uses a series of rollers, also called cylinders or drums, to apply ink to the paper. The first roller is the Plate cylinder, which has a thin metal or plastic printing plate with the images that will be printed. The Plate cylinder is treated so that certain areas attract ink while others repel it.
As the Plate cylinder spins, it contacts rollers that distribute a water solution and ink onto the plate. The ink sticks to the image areas, while the water solution repels it from the non-image areas.
The next roller is the Offset or Blanket cylinder, which has a rubber blanket around it. This cylinder turns in the opposite direction of the Plate cylinder. As the Plate cylinder rolls against the Offset cylinder, the ink on the plate is transferred to the rubber blanket. The Offset cylinder gets a mirror image of the ink design.
The final roller is the Impression cylinder, which turns in the opposite direction of the Offset cylinder. It’s a clean steel cylinder that presses the paper against the rubber blanket to transfer the ink. The image on the paper is now identical to the one on the plate.
Additional Points to Note
Each ink color has its own set of rollers, so an offset press used for four-color printing has four sets of rollers, one for each of the four CMYK colors. Similarly, a two-color offset press will have two roller sets.
Offset printing presses can be either sheet-fed or web-fed. Sheet-fed presses use single sheets of paper, while web-fed presses use a long, continuous roll of paper. Web presses are faster and are used for high-volume printing like newspapers, magazines, books, and catalogs.
Sheet-Fed vs Web-Fed Printing
Sheet-Fed Printing: Sheet-fed printing is a method where individual sheets of paper are fed into the printing press one after the other. This is a common method used for smaller print runs or for items that need to be printed on heavier stock paper. Sheet-fed printing is used for items like brochures, flyers, business cards, and letterheads.
Web-Fed Printing: Web-fed printing, on the other hand, uses a continuous roll of paper that is fed through the press. This method is usually used for larger print runs and is often used for printing newspapers, magazines, and catalogs. Web-fed printing can be more efficient for high-volume printing because it doesn’t require the press to be stopped and restarted for each sheet of paper.
Summary
Offset printing is called “offset” because the ink isn’t applied directly from the plate to the paper. Instead, it’s offset onto a middle roller before being transferred to the paper. The rubber surface of the middle roller reduces wear on the printing plate and extends its usable life.
Both sheet-fed and web-fed printing have their advantages and are used for different types of printing jobs. Sheet-fed printing is often used for smaller, high-quality print runs, while web-fed printing is more efficient for larger print runs and high-volume printing.
If you have any questions about printing, feel free to reach out to us at 718-928-6888 or submit our quote request form. We’re here to assist you in any way we can.
Take care!
Jeff @ New York Printing Center
