Pillbox

Lessons in lithography

Dating back to the 18th century, lithography is a method of printmaking unique for its chemical properties. Essentially, it is the process of printing on stone (lithos is the Greek word for stone), though no design is ever engraved onto the stone.

“In lithography, there is no physical change in the parts involved in printing,” said Heather White, an associate printer at the North Side studio and gallery Artists Image Resource (AIR). “Lithography is based on chemical change.” AIR’s lithography workshop features resources for a variety of projects, including printing on paper screens and on the surfaces of rocks. Traditionally, artists engraved their images on limestone; most modern lithography uses aluminum plates. “This way, we don’t have to grind off the top of the limestone to make it smooth,” White said.

Making a lithoprint

  1. First make a design on the surface of the stone or plate using an oil-based medium. A variety of oil-based media can be used — the more oily the substance, the more it will repel water, and the better the final print will be.
  2. The design has to be a negative of the image that will be produced on the final print, so everything has to be drawn opposite of what is intended.
  3. Coat the surface with an emulsion of acid and gum arabic. This creates a layer of salt around the image.
  4. Wash the oil off using turpentine.
  5. Remember to keep the surface wet with water throughout the process. Water is attracted to the salt layer around the image but doesn’t creep into the image.
  6. Apply an oil-based ink to the surface. Since the ink has oil and the original image had oil, the ink is attracted to the image and is repelled by the water around it.
  7. Use just the right amount of ink. “Too much and [the ink] would collect outside the plate and you would lose edge definition,” said William Rodgers, who heads the operations and workforce of AIR. “Too little and it won’t be a rich enough color.”
  8. Place the plate in the printing machine.
  9. Put the paper on the plate and start the machine.The machine applies pressure on the paper, transferring the image from the plate onto the paper.

Things get more difficult when there is more than one color in the picture. Each color must be printed individually, so multiple colors require multiple runs on the machine. The hard part here is to precisely align the paper and plate — artists usually fasten them together using pins. This way, the paper is in the same position each time the machine runs, and the lithoprint is not distorted.

History

Lithography was invented by Alois Senefelder in Bohemia in 1796. “Senefelder came up with lithography as a better way to print sheet music,” White said, “but the applications have since expanded.” Lithography is now used for making things ranging from posters to maps, in addition to artwork. Numerous French and American artists, including Pablo Picasso, used lithography for printmaking around the turn of the 20th century, and lithography continues to be popular among artists.

AIR artists create a variety of lithoprints, ranging from prints made on plain paper to prints made on stone. Many of the pieces involve a combination of lithography and other printing techniques.