Noun
scratchboard (uncountable)
(art) A technique in which drawings are created using sharp knives and tools for etching into a thin layer of white china clay that is coated with black India ink.
Scott created these drawings in scratchboard - an engraving medium which evokes the look of popular art from the period of these stories. Source: Internet
My favorite medium is scratchboard, which was a technique that my mother showed me when she was teaching. Source: Internet