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Printing is a process for reproducing text and image, typically with ink on paper using a printing press.

There are nine main types of printing processes:

* 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

Step1:- Pre-print
Before the job can be printed, the document must be converted to film and "plates." In the case of How Stuff Works Express, film negatives are created from digital files. Images from the negatives are transferred to printing plates in much the same way as photographs are developed. A measured amount of light is allowed to pass through the film negatives to expose the printing plate. When the plates are exposed to light, a chemical reaction occurs that allows an ink-receptive coating to be activated. This results in the transfer of the image from the negative to the plate.

There are different materials for plates, including paper (which produces a lower-quality product). The best plate material is aluminum, which is more costly.

Each of the primary colors -- black, cyan (blue), magenta (red), and yellow -- has a separate plate. Even though you see many, many colors in the finished product, only these four colors are used (you'll also hear this called the four-color printing process -- it's a little like the three-color process used in television).

Step 2: The Press Run
The printing process used to print How Stuff Works Express is called web offset lithography. The paper is fed through the press as one continuous stream pulled from rolls of paper. Each roll can weigh as much as 2,000 pounds (1 ton). The paper is cut to size after printing. Offset lithography can also be done with pre-cut paper in sheetfed presses.

Web presses print at very high speeds and use very large sheets of paper. Press speeds can reach up to 50,000 impressions per hour. An impression is equal to one full press sheet (38 inches x 22 and three-fourths inches), which is 12 pages of How Stuff Works Express. Immediately after leaving the oven, the paper is run through a short series of large metal rollers that have refrigerated water flowing through them. These chill rollers cool the paper down instantly and set the ink into the paper. If this were not done, the ink would rub off on your fingers.

Color control is a process that involves the way in which the ink blends together, and is tied closely to the plate registration. The amount of ink that is released into the units depends on how much ink is needed to achieve a desired look. The ink is adjusted via the control panel that is part of the overall control console. Prior to being placed on the press, the plates are scanned and the data is then transferred to a micro cassette. This serves as the "master" that directs the release of ink to pre-set values.

Step Three: Bindery
The bindery is where the printed product is completed. The huge rolls of now-printed paper are cut and put together so that the pages fall in the correct order. Pages are also bound together, by staples or glue, in this step of the process.

In the case of How Stuff Works Express, a machine called a stitcher takes the folded printed paper (called press signatures) and collates them together. Then stitches (staples) are inserted into the signatures, binding them together.

Step Three: Bindery
The bindery is where the printed product is completed. The huge rolls of now-printed paper are cut and put together so that the pages fall in the correct order. Pages are also bound together, by staples or glue, in this step of the process.

In the case of How Stuff Works Express, a machine called a stitcher takes the folded printed paper (called press signatures) and collates them together. Then stitches (staples) are inserted into the signatures, binding them together.