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Chris Easton - Press Room Management
{Basic principles of offset printing}

 By Chris Easton - Press Room Management

 

Basic principles of offset printing

Offset printing is a fairly complex process that is the most common form of printing used today. It is a process that uses mechanical and chemical aspects in order to reproduce images in large or small quantities. When this process was invented, it revolutionized the printing business making it possible to print large quantities of product much faster than ever before. It basically made Gutenberg’s movable type press obsolete. Today’s printing presses would certainly be mind boggling to Gutenberg.

In a nutshell, the offset process works like this: A thin metal plate with a light sensitive coating is exposed, by our plate making dept. personnel using a laser that “burns” the wanted image on the plate. The plate is then sent through a processor that removes all of the emulsion that was not imaged by the laser, washing it away. The remaining image is what will be printed on the press. The plate will be mounted to a cylinder in the press. The press has several rollers in it, which first applies a light film of water and then a film of ink to the plate. The water has several additives in it for control purposes, which we will not get into now. It is known as “fountain solution”.

Basically, water and ink don’t mix which is why this process works. The water is applied to the plate and the image, which was burned onto the plate, repels the moisture and the ink sticks to the image. On the flip side of this, the non-image area of the plate will pick up and hold the moisture, repelling the ink. The image is then transferred to a rubber blanket mounted to another cylinder. The image is backward at this point in the transfer process. Finally, the paper is run through the press between the blanket cylinder and a third cylinder called the impression cylinder. This is where the ink is transferred to the paper. The process can be repeated in the same press many times by having more printing units with the three cylinders and rollers described above. This is done for each color that the job requires.

Presses these days can come in many configurations that make it possible to do a number of things including the printing, perfing, scoring, folding, gluing, and many other processes, in one pass through the press.

Here at Beechmont Press, we employ only the best technicians in our field with the goal of the highest quality products and services for our customers and their complete satisfaction.

Article Written By: Chris Easton - Press Room Management


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