Carbon dust is a very beautiful, old medical illustration drawing technique wherein loose dust (filings from carbon pencils) is applied to board or heavy paper with a brush and manipulated with blending stumps and chamois cloths, primarily. Honestly, this piece has also seen the use of paper towel and my own body as tools. Then, erasers of all stripes, white conté/chalk, white gouache/watercolor, or even an exact-o (to scratch the surface back to the surface's tone) are used to create the spectral highlighting and surface textures. This is the largest drawing I've attempted in my artistic life. It's evolution has been very surprising and quite a departure from most of my (much much smaller) work.