Scratchboard art or Scratch Art is a form of direct engraving. The panel starts out solid black and then the artist scratches to expose a layer of white clay under black ink. The working surface is a three layer medium made up of a 1/8" masonite panel as a support (for ampersand scratchbord, which is what Luis V. Zimmerman works on; the support may be different in other brands).
The support is covered with smooth white clay followed by a thin layer of black India ink, leaving a solid black panel to start with. The artist then uses various tools to scratch through the black ink and reveal the white clay below.
Every line, dot and dimple is created by hand all with lines and dots and variation in tone and value are based on how many lines are scratched in a particular area or how much of the white clay that your eye sees. Colored inks can be added to the exposed white areas of the work if desired or the board can be left black and white. Large and complex pieces can take hundreds of hours to be completed due to the many layers of tiny scratches that cover the board.