TECHNICAL | PRINTING DEFINITIONS
LITHOGRAPHS are planographic prints. That is, they are made from a flat surface. This is a process, invented in the late 19th century, by which the artist draws on a stone or metal plate with an oil based crayon. (I used litho stones in the 1970s and now use solely aluminum plates.) By taking advantage of the fact that oil and water don't mix, the artist then fixes the image with a water-based solution and, naturally, the water does not adhere to the areas drawn on. Then she rolls the plate with an oil based ink (in any color) and the ink adheres to the areas drawn and is repelled by areas that are wet. Therefore, the ink only stays where the artist drew. Then she puts paper on top, pulls it through a press and the ink is again transferred from matrix to paper. The image can be re-inked many times without wear. There is a different stone or plate for every color. Often, the paper goes through the press many times to achieve the combination of colors the artist needs. Since lithography is a planographic process, no plate mark is created when a lithograph is printed. Lithography is the fundamental process of all commercial color printing.
A SILKSCREEN, or serigraph, is stencil type process using a fine mesh fabric stretched on a frame. The artist blocks out all the areas she does not want to have an image with paper, glues, photomechanical processes or other materials. She puts the screen on top of a sheet of paper, then squeegees ink through the mesh. Like any stencil, the ink will only come through where the artist wants it. There is a different matrix or silk-screen for every color. Often, the paper goes through the press many times to achieve the combination of colors the artist needs. My silkscreen colors are water-based, unlike my lithographic inks, which are solvent (grease)-based.
A GUM PRINT is basically the same as a lithograph, with the exception of the matrix. Instead of drawing on a stone or metal plate, the image is on a photocopied piece of paper. The artist then inks up the photocopy on paper as she would a lithograph, using very soft inks instead, so as not to disrupt the surface of the fragile paper. The inked photocopy on paper is then put in contact with the rag paper and put through the press. The image transfers to the rag paper and the used photocopy is thrown out. (If I want multiple impressions of the same image, I make multiple copies and use each one once.)
SOLVENT TRANSFER is another term for photocopy transfer. The artist transfers a photocopy image to paper by soaking the back of the photocopy paper with a solvent, such as acetone or lacquer thinner, and running it through a printing press. The solvent dissolves the toner and transfers it to the paper by the pressure of the press.
A PHOTOCOLLAGRAPH uses silk screen photo emulsion applied to a substrate, usually a thin wood board, such as luan mahagony plywood, masonite or door skin. After exposing a photo positive image onto the surface, the emulsion is then developed and washed away, leaving an image on the surface of the wood. The positive marks are now the exposed wood surface. This image is then processed as a traditional collograph etching, where you ink up the recessed areas of the plate and that and any texture on the plate take ink.