Planographic printing were called those printing procedures,
in which the image is printed from a flat surface.
This is chemically prepared in order to hold on to printing ink
in places from which they will after it transfered on the paper,
while rejecting it in these areas, which will keep blank on the paper.
The process utilizes the property that water will not mix with oil.
The classical planographic printing technique for artists is lithography, printing from a flat stone.
This technique is developed in 1789 by the German printmaker Alois Senefelder.
A special planographic printing procedure is silkscreen printing. Here were piece of porous, finely woven fabric (originally silk, but typically made of polyester since the 1940s) stretched
over a frame. This is called the screen. Areas of the screen are blocked off with a non-permeable material to form a stencil, which is a positive of the image to be printed; that is, the open spaces are where the ink will appear.
In the printing procedure a rubber blade (squeegee) press the ink through the open areas of the screen and transfer it on the substrate.
Substrate can be any material, which is flat or flexible.
Later (in 20th. century) other planographic printing procedures are developed, in which metallic material take the place of stone.