Planographic printing is the forerunner of offset printing, which was initially referred to as lithography. This technique was invented by Alois Senefelder around 1796 in Munich. The principle on which lithography is based is extremely simple: the drawing or engraving made on stone with greasy colours can be transported in the desired number of copies by chemical or mechanical action on paper, metal or other carriers.
Lithography is based on the following principles: Some stones (the so-called lithographic stones) absorb water very well; greasy and resinous bodies have the property of adhering strongly to the lithographic stone, from which they can be removed only by the action of a very strong acid or by strong rubbing with moist sand; greasy and resinous bodies have the property of repelling against water. When printing with a press, the sheet of paper receives only the ink that is deposited on the drawn parts and not on the other.
The surface to be used must be granulated until all markings or traces have been removed. The surface of the stone must be polished, it is drawn with a lithographic pencil or with lithographic ink made of fatty substances, the lithographic ink is known to be very oily. Calcium carbonate (the matrix) easily retains the fatty substances and on the stone the images have to be drawn in reverse.
The surface to be used must be granulated until all markings or traces have been removed. The surface of the stone must be polished, it is drawn with a lithographic pencil or with lithographic ink made of fatty substances, the lithographic ink is known to be very oily. Calcium carbonate (the matrix) easily retains the fatty substances and on the stone the images have to be drawn in reverse.
After completion of the drawing, the stone is brushed with a liquid based on nitric acid, acidified gum arabic and water. Printing takes place 24 hours after preparation with the lithographic press, the drawn matrix is wetted and then dyed with a rubber roller.
Lithographic printing is therefore based on the incompatibility of certain inks with water.
Over the years, planographic printing has undergone some improvements, such as the introduction of aluminium instead of stone in a very short space of time. After a century the first flat spindle machines were built and towards the end of the eighteenth century lithographic printing was associated with advertising, making it possible to print a considerable number of copies or advertising graphics. The result is a new industry, a new sector: print advertising.
Today, planographic printing is no longer used for large-scale distribution, but has developed into what we now call offset printing. The old lithography, which used stone as a matrix, is still used today by lovers of engraving and graphics.