The invention of the cel
Before cels, animators redrew the entire image — characters and background alike — for every frame. The cel changed that. By painting moving characters on transparent acetate and photographing them over a single painted background, studios could animate only what moved. The transparent-sheet technique was patented in the United States in the 1910s and quickly became the foundation of the industry.
The studio system
Through the mid-twentieth century, cel animation matured into an assembly line of specialized roles: storyboard, layout, key animation, in-betweening, tracing and inking, painting, background art, and camera. Each department handed work to the next, and the cel sat at the center — the physical object every other stage served.
Anime and the rise of limited animation
Post-war Japanese studios adapted cel animation to television budgets and schedules, developing an economical, expressive style sometimes called limited animation. Techniques like holding cels across frames, reusing backgrounds, and separating moving parts onto their own layers stretched every drawing further. The result was a distinctive visual language and an enormous body of production artwork.
From xerography to the digital transition
Hand inking gave way to xerography in the 1970s, speeding the transfer of pencil lines onto cels. The truly seismic change came in the late 1990s and 2000s, when studios moved to digital ink and paint: drawings were scanned and colored on computers, and physical cels stopped being made. Productions from the digital era onward have genga and douga on paper but no painted cels at all.
Why the artifacts survive
Because cel animation was a physical process, it left behind millions of drawings, cels, and paintings. Much was discarded or recycled at the time, which is exactly why surviving production materials — especially original cels with matching backgrounds — are prized today as both art and history.