I just read an mind-popping article by Julie L. Belcove about Jasper Johns and monotype (WSJ Magazine, Feb. 9, 2016). Here is a paragraph from it:

"Monotypes are a peculiarly immediate and intimate form of printmaking. Unlike, say, an etching, which once created allows a printer to apply ink at a later time and repeatedly produce multiples, for a monotype the artist in one sitting paints directly on a smooth surface, or matrix, such as a sheet of Plexiglass. Then, before the ink has a chance to dry, the matrix is run through a press, transferring the image to a piece of paper. "'They're uncategorizable. They are prints, but you could just as easily argue they are drawings or paintings,'" says [Jennifer L.] Roberts [a professor of art history at Harvard, who is co-writing a catalogue raisonne of Jasper John's monotypes].

"'It's a space for rapid, intense experimentation. The matrix is essentially destroyed in the process of creation. It's like life. There's no fantasy you can keep creating this image. There's something haunting.'"