Martin was one of the first artists to apply the mezzotint technique to steel. A rocker, a tool with a curved serrated blade, is used to roughen the entire surface of a copper plate, creating burrs, or tiny hooks of metal, that hold ink for printing. Flattening out the burrs with a burnisher, a small spoon-like tool, creates smooth areas that print white. This process lends itself perfectly to the subject: the sun, moon, stars, lightning, billowing clouds, and figure of God are made visible by eliminating black.