Steatite and Calcite Natural White Chalks in Traditional Old Master Drawings

Abstract

This article examines the history, geology, chemical composition, sources, production, and physical characteristics of natural white chalks when used as traditional old master drawing materials. The nomenclature of white chalks is presented to clarify the relationship of natural white chalks with respect to other types of white chalks, including fabricated and artificial white chalks. Specimens of two types of natural white chalk, steatite natural white chalk and calcite natural white chalk, were obtained and studied using optical microscopy and field emission scanning electron microscopy to observe their appearance and to learn more about their working properties. Their chemical composition was determined using x-ray diffraction analysis and field emission scanning electron microscopy with energy dispersive x-ray spectroscopic microanalysis. These results were compared with the physical characteristics and chemical composition of traditionally used steatite and calcite natural white chalks documented in the historical record.