Trois Crayons refers to a drawing technique using three colors of chalk: red (sanguine), black, and white. The paper used may be a mid-tone such as grey, blue, or tan. Among numerous others, the French painter Antoine Watteau drew studies of figures and drapery using trois crayons. - Wikipedia
The technique may be used to organize the light relative to form, to create emphasis, rhythmic dialog, and balance.
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