Natural black chalk in traditional old master drawings

The history, geology, sources, production, and physical characteristics of natural black chalk as a traditional drawing medium were examined. Using field emission scanning electron microscope imaging, specimens of natural black chalk from Normandy, France, were studied in both unprocessed block form and as marks and lines drawn on paper. The physical characteristics of insolubility in water and variation in hardness with differing storage conditions were evaluated; chemical composition was determined using field emission scanning electron microscopy with energy dispersive x-ray spectroscopy microanalysis. Results were compared with the physical characteristics and chemical composition of traditional natural black chalk as documented in the historical record.