By: Brad Kartel
Submitted: 2011-08-31 08:59:11 | Word Count: 594
Looking back, lithography took a great turn with the invention of the offset printer. These machines provide cleaner and sharper reproductions of images as compared to the letterpress of the past. They are also cheaper to operate because they work really fast.
But nowadays, we also have sheet fed printers. These machines only print on small sheets of paper, from A4, to short size, and then the biggest would be around 12" x 18". Sheet fed printing is for those small jobs that are not viable to be printed on the big machines.
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As we remember the history of printing, it was the German Alois Senefelder who first showed lithography when he printed on a flat, smooth-faced rock sometime in the 1700s. He knew that water and oil do not mix so he sketched an image on the stone using a greasy substance that was easily absorbed by the rock. When his design was set, he put water over it, but naturally, the water just slid across the image and did not harm it. He then pressed the stone on a piece of paper and the image was transferred cleanly. That was the first recorded stint at lithography.
Half a century later, the French developed the earliest steam lithographic offset printing machine. But when the 1950s came, offset printing was the most widely accepted system of printing because it can print big volumes of materials at high speed. Newspapers and books were finished very fast and we saw the emergence of many books and other printed materials.
Our modern printing process combines the elements of photography with Senefelder's principle of using oil to repel water. That is why offset printers come with printing plates that are made of thin paper, metal, or plastic. But these are all photo sensitive. The plates are then sensitized by coating them with diazo compound that make printer-ready after exposure to light. Other kinds of printers use pre-sensitized sheets of aluminum with granular finish.
The pre-press part of the printing process starts with the camera-ready copy. This copy was already corrected and should resemble how the actual printed material will look like. The client approves the camera-ready copy for printing. The copy is then made into a negative and then transferred onto a plate to be readied for the offset machine.
While there are so many developments on the printing machine to make it work faster and more efficient, the basic principles are still there. However, more modern machines no longer need a lot of people to operate. Sometimes it only needs one person to operate the color separating machine, the plating, and then the actual printing. He may just need assistance when loading the roll of paper onto the machine. But for bigger machines, the loading is also done mechanically.
Meanwhile, there is the branch of printing called the desktop publishing. Most printing shops carry this service for those small orders because there are still a lot of people who need some small print jobs. Some of these projects are birthday party invitations, the specialized wedding invitations, calling cards and stationeries or memo pads. These are too small and too expensive to run in web presses, so instead, they are processed using sheet fed printers. Sheet fed printing does not require photography and plating but is run mostly by a computer.
Author Resource:-
Brad Kartel is a marketing executive whose passion is helping business owners build their campaign through sheet fed printing of marketing materials. Learn more about these sheet fed printers.
