Did you ever wonder how your daily newspaper is printed?
Without going extremely deep into all of the highly technical details, and there are many, here is the basic process:
Once the stories are written, pages are blocked, and type is set using computers, the page is engraved into plates that are installed in the press. Printing plates are very thin pieces of plastic or metal, depending on the printing application, upon which the image of the text and photos to be printed are electronically engraved.
The plates are installed on a round carrier in the press, where high spots that form the type and photos are lightly covered with ink by an ink-covered roller.
The paper to be printed passes over the plate, and a roller above the paper presses the paper to the plate insure that it comes in solid contact with the inked plate. This transfers the image from the plate to the paper.
Four inks are used to print a full color photo -- cyan, magenta, yellow, and key (black). In order to reproduce color text and pictures, four carefully-aligned plates must be prepared, one for each color.
Thousands of colors can be made by combining cyan, magenta, and yellow in addition to black in various combinations. Different colors are obtained by overlaying tiny dots of cyan, magenta, and yellow overlapping them at different degrees to obtain the desired color when combined with the white background.
Each color of ink subtracts brightness from the white paper used as a background by absorbing particular light wavelengths. Depending on how the ink is applied, they may absorb some or all of certain colors. Additional colors are obtained by spacing the dots at different widths.
Halftoning (also called screening) permits less than full saturation of the primary colors, so the tiny dots of each primary color are printed in a pattern small enough that the human eye perceives the combination as a single color. Magenta printed with a 20% halftone, for example, produces pink, because the eye perceives the tiny magenta dots and the white paper between them as lighter and less saturated than pure magenta ink. A full, continuous color range can be produced by halftoning.
The distance between the dots depends on the kind of paper being printed. Newspapers, which use cheap newsprint, use screens with a "frequency" of 60 to 120 lines per inch (lpi) to reproduce color photographs. The coarser screen produces a lower quality printed image, but is necessary because newsprint is highly absorbent. Coated paper used in magazines and books allows 133 to 200 lpi and higher screens to be used, resulting in more photograph-like pictures.
The color black results from a full combination of all colored inks, but the resulting black is not a deep, high-quality black. Therefore, and also for economic reasons, black ink is used with the cyan, magenta, and yellow to produce sharp type and detailed photographs. It is also cheaper to use a black ink than to use the required amounts of the other colors.
On a sheet fed press, like those used to print letterhead, brochures, photographs, and other single page flat stock, the paper must be run through the press four separate times, cleaning the press and inking it with a different color before each run. However, newspapers are printed on what is called a web press, which uses large rolls of paper that are continuously fed through the press instead of flat sheets.
Rather than printing only one color like a sheet press, the web press contains four printing stations, one for each ink color. After all printing is finished, the press folds and cuts the paper into the proper length of your daily newspaper.
