Carbon dust

Popularized by Max Brödel, the carbon dust technique became widely used among medical and scientific illustrators in the twentieth century.

The namesake of the technique consists of applying carbon dust, obtained by rubbing carbon pencils against an abrasive surface such as a metal file, to a prepared surface via dry brushes. Highlights may be painted on or scratched out later in the process.

References

Hodges, Elaine R.S. The Guild handbook of scientific illustration. Hoboken, NJ: John Wiley & Sons, Inc. 2003.