How did Edgar Degas use charcoal and pastel together in his late artworks?

In his later years, Edgar Degas utilized a sophisticated method of combining charcoal and pastel to create series of related compositions. Beginning in the early 1880s, he experimented with producing initial images as charcoal drawings on tracing paper.1

He would retrace these drawings multiple times, allowing him to manipulate subtle nuances of gesture and detail across a "family" of works. By layering pastel over these charcoal foundations, he moved beyond simple subject matter to focus on the fundamentals of picture-making—specifically color, form, and composition. This technical approach enabled him to produce long sequences of closely linked compositions, which became a hallmark of his later, more simplified, and expressive style.12