Lithographic printing systems

The invention of lithography and then offset printing marked a revolution in the graphic arts and publishing industry

Offset printing is the offspring of lithography, a process discovered by the German playwright Aloys Senefelder at the end of the 18th century when he experimented with greasy ink on the smooth surface of limestone. In fact, the word lithography derives from the Greek lithos, stone, and graphe, drawing.

This printing technique works on the principle that water and greasy substances are not miscible, so that a drawing or text is traced with oily ink on the stone (currently mainly metal plates are used), while the rest of the surface is treated with a substance that makes it more water-repellent, then it is moistened, greasy ink is applied, which adheres only to the original outline, and finally the sheet of paper on which the image is to be transferred is stamped. In the beginning, Senefelder used lithography to print his musical scores cost-effectively, but the discovery soon opened up a wide range of publishing, artistic and advertising possibilities.

The advantages of lithography

Lithography is a direct printing method in which an image engraved on a metal plate or flat stone is transferred to the substrate through direct contact. Only the inked parts become printed on the paper. By contrast, offset printing is an indirect printing method in which, based on the same principle, the image is transferred from the plate to a rubber roller or blanket, and from there to the substrate. In this way, the paper remains dry and the operation can be repeated at high speed.

In the 1930s, the French printer Godefroy Engelman developed chromolithography, i.e. lithographic colour reproduction. In the early days, it was required to prepare a different stone with the original image for each colour, always obeying the same principle of incompatibility between the greasy ink and the surface moistened with water. Thus, the printing substrate had to be stamped as many times as the number of colours that were to be transferred.

This technique marked the birth of an artistic discipline of great creative wealth, which over the course of a century was explored in depth by artists such as Goya, Toulouse-Lautrec, Ramon Casas, Picasso and Andy Warhol, all of whom left their mark on an era.

The birth of offset print

In 1853, the English scientist John Strather patented offset lithography or offset printing, although it was not until two decades later, thanks to the incorporation of rubber cylinders, when it began to be used on flatbed presses to print on metal. Along with the invention of phototransfer, the new method revolutionized the graphic arts and publishing industry.

Lithographic printing on modern rotary and semi-rotary offset presses, such as those manufactured by ROTATEK, provides high quality prints at a high speed. It reproduces any phototransferible material onto the printing plates and can be used on a wide array of substrates. Due to these advantages, more than 40% of all jobs in labels, packaging, editorial printing and advertising materials are produced by offset.