Lithographic Presses

Lithography, invented in 1796 by the Bavarian Alois Senefelder, was a method of printing that demanded an entirely new kind of printing press. Prints were made from blocks of stone, and because the stone was both flat and rigid it required perfectly even pressure across its surface—something that could not be achieved with a platen press. But the stone was also brittle, and easily broke, under too much pressure, such as the narrow line of extreme pressure under a turning cylinder. One solution was to use a leather-covered scraper bar about two inches wide, which was drawn across the stone to give a moving band of pressure. Later the stone was replaced with a metal plate that could be printed on a conventional cylinder press.

At first Senefelder experimented with platen and cylinder presses. Then he tried rubbing the stone with a piece of polished wood—the precursor of the scraper press, which was to dominate the next fifty years. The earlier scraper presses—the pole presses—were large devices in which the scraper was on the end of a long pole, pivoted from the top. The scraper was pulled through an arc across the stone. By 1820 scraper presses were much smaller, and there were even portable models.

The lithographic hand press of the nineteenth century survived into the twentieth century, but in a new role. As commercial lithographic businesses converted to faster machines, they built libraries of images stored on stone. When an image was needed for production, a proof would be taken at a hand press and then offset, or transferred, to another stone or plate for printing. Hand presses became known as transfer presses. This was a modification of the transfer method of printing on tin that had been practiced since the 1860s: a series of color impressions was taken (in reverse order) onto a sheet of varnished paper, then the paper laid face down on tin plate and pressed. In transfer printing, the intermediate surface—paper—is destroyed during the process.

Offset printing in the modern sense—printing on paper—was developed around 1903 by Ira Rubel. At the time, commercial lithographers used flatbed cylinder machines, the cylinder being covered by an elastic tympan sheet. According to legend, printers often observed that an impression taken accidentally on the tympan sheet and transferred to the back of the next sheet of paper was clearer than a print taken direct to paper. Rubel built a machine on the observation. An almost identical process using an intermediate rubber-covered cylinder had been used by European tin printers since 1877, but there was apparently no connection between that and Rubel’s invention.