Lithography
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Lithography

 

Lithography is the art of printing from stone.  The process was invented by Alois Senefelder in 1796, and the fundamental principles that he established have remained unchanged.  By writing or drawing with a greasy ink on a specially prepared slab of limestone, the grease is absorbed by the stone and the image thus formed has an affinity for printing ink, while the remaining parts of the stone repel the ink as long as the surface is kept moist with water.

After the invention of photography in the mid-nineteenth century and the production implications led to a dramatic technological innovations taking place.  The use of photographic techniques for reproduction allowed more visual images to be produced.

Lithographic presses are cylinder machines for printing from the lithographic stone or plate.  In early models c1860 the stone was fixed to a bed which moved to and fro beneath a cylinder.  The next major advancement was the introduction of the 'direct rotary' press with two cylinders, which, when printing, revolve continually in contact with each other.  On one cylinder is the plate and the second carries the sheet. Around 1908 the 'offset press' was introduced which enables fine lines and half-tone dots to be printed on either smooth or rough-surfaced paper.  The off-set machine consisted of three continually revolving cylinders.  The first carrying the printing plates with its damping and inking mechanism which makes contact with the rubber blanket moulded on the middle cylinder; the blanket offsets the design to paper, carries by the third cylinder.