Carborundum mezzotint is a printmaking technique in which the image is created by adding light passages to a dark field. It is a relatively new process invented in the US during the 1930s by Hugh Mesibov, Michael J. Gallagher, and Dox Thrash, an artist working in Philadelphia with the WPA). "Carborundum Collagraph" collagraph is a different printmaking technique, invented in 1952 by Henri Goetz, an American abstract artist living in Paris. The carborundum mezzotint uses the grits to create pits below the surface of the metal that then hold ink, like traditional mezzotint. The carborundum collagraph creates the image above the surface of the matrix, which does not have to be metal. In one method, the grits are mixed into a paste using an acrylic base that is painted onto the matrix, creatin