Web offset is a form of offset printing in which a continuous roll of paper is fed through the printing press. Pages are separated and cut to size after they have been printed. Web offset printing is used for high-volume publications such as mass-market books, magazines, newspapers, catalogs and brochures.
There are two methods of web offset printing, known as heatset and coldset (or non-heatset). In the heatset process, the ink is dried rapidly by forced-air heating. In the non-heatset or coldset process, the ink dries more slowly by ordinary evaporation and absorption.
Some web offset presses transfer text and images to only one side of the print medium at a time. Others can print on both sides simultaneously. The paper width is usually between 11 and 56 inches (approximately 28 and 142 centimeters). The paper is fed through the system at speeds ranging from 5 to 50 feet per second (approximately 1.5 to 15 meters per second).
Web offset printing differs from sheet-fed offset printing, in which individual pages of paper are fed into the machine. Sheet-fed offset printing is popular for small and medium-sized fixed jobs such as limited-edition books.
Printing is a means of graphic communications. It is the reproduction of quantities of images, which can be seen or perceived visually. Regardless of the great number and variety of printed products they all have one thing in common; each has the same visible image produced in quantity.
Today’s printer owes much to the Age of Science, particularly to electronics, computers, chemistry, optics and mechanics. Modern printing has become highly sophisticated. While the mechanics of printing has not changed greatly, the surrounding other technologies have. As new pre-press systems, plate, electronic controls, and paper have been developed along with other products of modern science and research, printing has gradually been transformed from an art to a science.
