Various types of printing processes

There are nine main types of printing processes used by most printing companies in the world:

* offset lithography - what we are exploring in this article
* engraving - think fine stationery
* thermography - raised printing, used in stationery
* reprographics - copying and duplicating
* digital printing - limited now, but the technology is exploding
* letterpress - the original Guttenberg process (hardly done anymore)
* screen - used for T-shirts and billboards
* flexography - usually used on packaging, such as can labels
* gravure - used for huge runs of magazines and direct-mail catalogs

Any well known printing company will tell you that offset lithography is the workhorse of printing. Almost every commercial printer does it. But the quality of the final product is often due to the guidance, expertise and equipment provided by the printer.

Offset lithography works on a very simple principle: ink and water don't mix. Images (words and art) are put on plates (see the next section for more on this), which are dampened first by water, then ink. The ink adheres to the image area, the water to the non-image area. Then the image is transferred to a rubber blanket, and from the rubber blanket to paper. That's why the process is called "offset" -- the image does not go directly to the paper from the plates, as it does in gravure printing.

What exactly is photo offset

The most common kind of offset printing is derived from the photo offset process, which involves using light-sensitive chemicals and photographic techniques to transfer images and type from original materials to printing plates.

In current use, original materials may be an actual photographic print and typeset text. However, it is more common — with the prevalence of computers and digital images — that the source material exists only as data in a digital publishing system.

Offset litho printing on to a web (reel) of paper is commonly used for printing of newspapers and magazines for high speed production.

History of Offset printing company

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 letterpress machine. A cylinder (see figure below) 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 1950s. 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.