The basic principle of Lithography was discovered by Alois Senefelder of Munich in 1798.
Senefelder was working with a highly porous stone and sketched his design using a greasy substance. He then wetted the entire surface with a mixture of Arabic gum and water.
Only the stone areas absorbed the solution, the design area repelled it. Senefelder then rolled on an ink made of soap, wax, oil and lampblack – this greasy substance coated the design but did not spread over the moist blank area. A clean impression of the design was made when a sheet of paper was pressed against the surface of the stone.
Lithography received its biggest boost in the 1900’s when new recognition and popularity encouraged printers to find more practical and faster methods of printing illustrations.
By the 1950’s, lithographic printing was the most popular production method as plates, inks and papers all improved. Even today, it continues at the heart of the modern printing industry, delivering sharp, clean images.
In lithography printing, the plates are made from exposure to a light source with an overlaid film, or using a machine that exposes the plate using lasers direct from a computer. This plate is then fitted around a cylinder which has ink rollers in contact with it (ink is the oil) and is also in contact with cylinders that sit in a fountain solution (containing Water).
When the plate is turned through the rollers, the water sticks to the un-etched coating and the ink is then picked up by the etched surface. As the oil and water don’t mix, it means only the etched image picks up ink and applies it to the next cylinder. This cylinder in turn then applies the ink to the paper by way of compressing it between an impression cylinder and a blanket cylinder, which has a rubber surface to apply the ink to the paper. This process is repeated across four plates on the same printing press, one for each colour (CMYK) to produce the final printed image.
As a guide, lithographic printing is mostly used for full colour print orders, with quantities over 500 sheets. This is due to the setup costs required to create the four printing plates and prepare the press, but once running it offers significant savings against digital production methods.
The main benefits of lithographic printing are the unrivalled print quality, the cost-effectiveness in high volume jobs, speed and that it is the most flexible process when choosing options for printing stocks and finishes.
Lithography is used for medium and long print runs of products such as magazines, posters, packaging, brochures and stationery and can print up to A1 size.
Author: Gavin Ellis, Print & Studio Manager Far’n’Beyond
