The contemporary artist Brian McSweeney began his career as a traditional 2-D cel painter. What is a cel?

A cel, short for celluloid, is a transparent sheet used in traditional animation to paint characters and objects, which are then layered over a static background. This technique allows animators to create the illusion of movement by replacing only the painted cels while keeping the background unchanged. Cels were commonly used in classic animation before the advent of digital techniques, facilitating the production of animated films and television shows.