A lithograph is a printing method which dates back more that 200 years. It began with “stone lithography,” a process by which an artist’s work was rendered onto a stone and with the use of various solutions that either attract or repel ink, the stone essentially became a stamp which could be pressed or rolled onto paper to transfer the image.
The modern version of this technique is a process called “offset lithography”. Before a lithograph can be produced, the image is separated into four colors: Cyan (Blue), Magenta (Red), Yellow and Black (i.e. CMYK). Since most colors in the spectrum originate from these colors, when they are combined to varying degrees, they can reproduce most color that may be found in the original work. For this reason, this process is also commonly referred to as “Four Color Process” printing.
Offset lithography operates on a very simple principle: ink (which is oil based) and water don’t mix. First, each of the four separated colors are transferred to their own individual aluminum plate. During the printing process, each plate is dampened first by water, then ink. The ink adheres to the image area, the water to the non-image area. The image on the aluminum plate is then transferred like a stamp onto a rubber blanket creating a negative image, then the rubber blanket is rolled across the paper to create the final positive impression of that color onto the lithograph. When all four colors are layered onto the same paper sheet (and in proper registration) they combine to create the final image.