One of the more popular stops at the National Center is the printing plant. This state-of-the-art facility has two two-color presses and one five-color press. They print an average of 4-5,000 sheets per hour, but can print up to 6,000 per hour.
The printing plant produces about 4,000 different maps annually. The average number of copies per map is 2,500 (a 5-year supply). Thus about 10 million copies of maps are produced per year. More than a dozen different kinds of maps are printed; nonmap printing is done elsewhere. Most maps are shipped to the Denver distribution center in Denver, Colorado, where maps are sold on site and where all orders are centrally handled.
These presses use a process called lithographic offset printing. Map images are separated into basic printing colors and made into negatives, which are used to transfer the images to aluminum plates.
Aluminum plates are mounted on drums in the press. When the press runs, water and then ink are rolled onto the plates. The images on the plates are greasy, which causes them to repel the water but attract the ink. The water-soaked aluminum repels the ink. The images on the plates are then transferred to a "blanket" cylinder, which in turn transfers them to the paper.
Since maps are printed on large sheets of paper, they must be trimmed to size. Our large guillotine-like paper cutter has a 6-foot cutting blade that cuts 1,000 sheets (a 4 1/2 inch stack) at a time. The cutting blade is replaced about every 6 months.
Map paper (E-30) is used for standard maps, coated matte paper for orthophoto and other special maps, dull coated paper for imagery maps, and "polyart" (water resistant) paper for National Park maps.
The printing plant uses about 2 million pounds of paper per year or 7 million sheets, an amount which equals 900 skids. All waste paper is recycled, along with the aluminum plates, soy-based ink, and silver from the film. The presses use about 9,000 pounds of ink annually.
