The printing press opened reading and artwork to the masses, and the innovation of lithography in 1798 made it easier for artists to use this technology. A printing press works by applying ink to a relief image and then transferring the upraised ink to a medium. This required artists to think backward about their art and carve it into a surface instead of drawing onto one. Lithography, literally drawing on stone, changed that.
Stone lithography is the process of an artist drawing with a greasy substance on a stone and then wetting it, allowing water to soak into the parts of the stone not protected by the grease. Oil-based paint is then rolled onto the rock, sticking to the grease and avoiding the water. Paper or cloth pressed to the artwork will absorb the color and display the artwork.
Flexography is a similar process that evolved from lithography and used high-speed rollers and engraved rubber plates. This process uses anilox rolls with a metal core and a ceramic surface with indented cells to hold ink. If your shop uses both methods, it is crucial to keep your anilox roll cleaner separate from your stone plate cleaners as the chemicals ideal for one may damage the other.
These days, lithographic plates are usually made of metal and will stamp the image onto a rubber mat which is then used to stamp the product. Industrial printing needs tend to use flexography over lithography. However, larger art producers will still use the metal, and there are many collectors of lithographic plates from famous or favorite artists.
You can still find artists using limestone, which is ideal for limited-run prints because the stones can be ground down for reuse. While having an artist paint with a particular medium on limestone can be more natural for creating unique artwork, it has limitations. Lettering is reversed in the painting, you need a separate stone for each color, and big mistakes mean grinding the stone clean and starting over. Once the artwork is finished, it is etched into the stone with a chemical reaction to make the design more accepting of ink and the surrounding rock more accepting of water.
Lithography today is used in making fine art prints, art installations and teaching situations. Other developments built on this printing technique, such as flexography, are more common in industrial printing, such as packaging labels.