We are asked to think of how tone can create or change the atmosphere of a drawing, looking in particular at the work of Odilon Redon. What I find interesting about his work is the progression I can see from his earlier works in charcoal to the later ones in pastel.
His charcoal paintings are very atmospheric, sometimes dark, surreal or mystical; he worked the charcoal, manipulated it to express his intention. He applied the charcoal over the entire page, also ground and applied with a brush, which he could then move about, or erase with a putty rubber to expose the white paper underneath. He used fixative to create layers which he could then also work into. The fixative, over time created a golden hue. He was aware of this but continued with the practice. That was the only colour that appeared on his charcoal drawings however.
Gradually he started to add pastel colours to his drawings. Initially he would complete a charcoal drawing as a first layer and then cover it in pastel. Also using fixative to progress between the layers and continuing with the same manipulation of the material he was using. Eventually he was able to work directly in pastel. He had learned, through practice on charcoal, to make tone do his bidding, and was able to progress to do the same with colour.
Ref: The American Institute for Conservation, A Technical Investigation of Odilon Redon’s Pastels and Noirs by Harriet K Stratis (1995)