Complex sentence: The traditional and most common support (material to which the paint is applied) for watercolor paintings is paper; other supports include papyrus, bark papers, plastics, vellum or leather, fabric, wood, and canvas.
Split into simpler sentences: The traditional and most common "support --" material to which the paint is applied--for watercolor paintings is paper. Other supports include papyrus, bark papers, plastics, vellum or leather, fabric, wood, and canvas.