Types Of Offset Presses
Offset presses are primarily of two types:
- Sheet-fed Offset Printing Press: In this kind of offset press the printing is carried out on single sheets of paper as they are fed to the press one at a time.
- Web-fed Offset Printing Press: In this kind of offset press the printing is carried out on a single, continuous sheet of paper fed from a large roll. The sheet is then cut into individual sheets of desired sizes.
There are many more differences between the various types of offset presses.
The Offset Printing Process
The offset printing process requires a fairly large investment in equipment and set up. However, once the infrastructure is in place, offset printing itself is relatively inexpensive. There are many things to know about the offset printing process from creating the artwork to operating the press and binding.
Offset printing history
Using an offset printing press to print on paper was probably done first by Ira Washington Rubel, an American, in 1903. The inspiration was an accident. While operating his lithographic press he noticed that if he failed to insert paper the stone plate would transfer its image onto the rubber impression cylinder. When he then placed paper into the machine it would have the image on two sides, one from the stone plate and one from the rubber impression cylinder. To Rubel’s amazement, the image from the rubber impression cylinder was much clearer; the soft rubber was able to give a sharper look than the hard stone litho plate. Soon he created a machine that repeated this original “error”. This process was also noted by two brothers, Charles and Albert Harris, at about the same time. They produced an offset press for the Harris Automatic Press Company not long after Rubel created his press.
The machine created by the Harris Automatic Press Company was based on a rotary letter press machine. A cylinder was wrapped with a metal plate that was pressed against ink and water rollers. Just below the metal plate cylinder was a blanket cylinder. Below that was an impression cylinder which fed the paper against the blanket cylinder so that the image could be transferred. While the basic process in offset printing has remained the same, some modern innovations include two sided printing and using large rolls of paper fed into the machines.
Offset printing became the most dominant form of commercial printing in the 1950’s. This was in part due to industry improvements in paper, inks, and plates. These improvements allowed for greater speed and plate durability. The majority of modern day printing is still done using the offset printing process. Even the high volume newspaper industry uses offset printing.
Although offset printing does the lion’s share of today’s business printing, some very limited editions of fine quality books are still produced using the letterpress, often in combination with offset methods. Some people still prefer the slightly embossed look that is only achieved with the direct contact of the plates with the printing medium. These specialty books are sometimes printed using individually set type pieces.
Your source for all information pertaining to the production aspect of the printing industry.