A term describing a printing process in which the image area and the non-image area co-exist on the same plane, in contrast to letterpress (printing from raised type) or gravure (printing from etched or engraved cells). Lithographic printing is based on the principle that oil and water do not mix readily (although a minute amount of mixing is necessary for lithography to work); the image area of a lithographic printing plate will attract a greasy, oil-based ink, while the non-image areas will attract water, mutual chemical repulsion keeping the two regions separate. The term lithography (which comes from the Greek words lithos meaning "stone" and graphia meaning "writing") originally referred to the use of special stones (a variety of calcium carbonate) on which lithographic printing was first performed (see below). In modern parlance, lithography refers to the use of aluminum plates which have replaced lithographic stones (also called, more accurately but less popularly, planography). Offset lithography refers to lithographic printing in which the inked plate first transfers the image to a rubber blanket, and the blanket then transfers the image to the paper or other surface. Lithography encompasses such processes as sheetfed offset lithography, web offset printing, direct lithography (also called Di-Litho), and waterless printing.

The inventor of lithography, Alois Senefelder (1771:1834) was the son of a German actor, and had attended the University of Ingolstadt in Bavaria, hoping to pursue a career in law. In 1792, his father died, and he could no longer afford to pursue his studies. He turned to writing plays, and, trying to find a way to inexpensively print them, spent a good deal of time researching various types of printing. He began with copperplate engraving, and since a certain type of Bavarian limestone was less expensive than copper, he tried using the principle of copperplate engraving on the stone. It is said that by accident he stumbled acoss the idea of lithography, but actually he had been carefully researching the idea for some time.

Using a slab of limestone (in particular, that from Kelheim in Bavaria), Senefelder was able to transfer a grease-based design or text to the surface of the stone, which was porous enough to accept a greasy ink. The non-image areas of the stone would, with the application of water, repel ink. Thus, lithography does not use a raised printing surface with which to make the impression. Senefelder was given by the Prince-Elector of Bavaria, Max Joseph, an exclusive 15-year license to develop the process of lithographic printing. In 1809, the King of Bavaria appointed him the Royal Inspector of Lithography, and he spent the rest of his life—profiting quite nicely from the invention—further developing and refining the process. In 1817, he created a working model of a lithographic printing press, and at the same time developed paper printing plates, with which he wanted to replace the bulky and unwieldy lithographic stones. He travelled throughout Europe extolling the virtues of the process and, in 1834, died. Unlike many of the inventors in the history of printing and the graphic arts, Senefelder was monetarily successful, won many prizes and medals for his invention, published books on the process, and was roundly praised and appreciated by his contemporaries.

Initially, lithography was used primarily for artistic expression and illustration, but advances in photography, press design, and platemaking made it a viable and popular commercial printing medium. The advantages of the lithographic printing process included the ability to print on rougher substrates than was possible with traditional letterpress methods. At the beginning of the twentieth century, however, lithography was falling behind letterpress, as new photomechanically-produced image carriers were better suited to letterpress process than stone printing. The stones themselves were taken out of the process and replaced with zinc and aluminum plates, a substitution that Senefelder himself had suggested some time before they actually went into widespread use.

Between 1881 and 1906, the process known as offset lithography was developed by accident, which added to the lithographic system the press blanket. Thus, in offset lithography, the plate does not come in contact with the substrate; the inked plate transfers the image to the rubber blanket, which then transfers it to the paper. The advantages of this process include the ability to print with a softness and richness of tone hitherto unknown; the conformability and flexibility of the blanket also created the ability to print on a wider variety of surfaces than was previously possible. Although offset lithography had inauspicious beginnings, during and after World War II lithographic platemaking and ink formulating vastly improved the quality and efficiency of the process. Offset lithography is the most common printing process today, and has spawned several varieties, including sheetfed offset (which, as its name implies, prints onto individual sheets of paper or other material), web offset lithography (which prints onto a continuous paper web or roll), direct lithography (or the printing of lithographic plates directly onto the substrate without an intermediate, offsetting blanket), and letterset (in which specially formulated silicon-based plates are designed to be used without the need for water). (See Offset Lithography.)

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