What role did oil sketches play in Peter Paul Rubens’s painting process?

In the painting process of Peter Paul Rubens, oil sketches—often referred to as a modello—served as a vital preliminary step for large-scale projects.1

These small-scale paintings on panel allowed Rubens to establish the composition and design before the execution of a final work. His process typically involved the following stages:1

• Conceptualization: Rubens would create an oil sketch to map out the composition, which he would then supplement with preparatory drawings of individual figures.1
• Delegation: For major commissions, such as tapestry cycles or large-scale decorative programs, assistants would use these sketches to enlarge the design onto a full-scale canvas.1
• Finalization: While assistants often handled the execution of the full-scale work, Rubens would personally paint key areas and thoroughly retouch the finished piece to ensure it met his standards.1

These sketches were essential for managing his prolific studio, enabling him to oversee vast decorative programs while maintaining his signature style. For instance, he produced more than 60 oil sketches for the Torre de la Parada hunting lodge, and his sketches for the Jesuit church in Antwerp were noted for the "great speed and frenzy of his brush".213