December 1914 (patent filed) · United States
The cel process is patented and licensed
The transparent sheet that made an industry possible
In December 1914 an animator named Earl Hurd filed a patent for drawing moving figures on transparent celluloid sheets laid over a single painted background. It is an unglamorous document about materials and registration. It is also the single most consequential production idea in the history of the medium.
| Date | December 1914 (patent filed) |
|---|---|
| Technique | Cel animation |
| Production type | Technique and tools |
| Artist, studio or institution | Earl Hurd and John Randolph Bray, Bray-Hurd Process Company |
| Country or region | United States |
| Period | The 1910s |
In summary
Drawing moving figures on transparent celluloid sheets laid over a single painted background, held in alignment by registration pegs, eliminated the need to redraw static elements for every frame.
Everything that stays still should be painted once. Everything that moves should be drawn on glass.
The problem it solved
Before the transparent overlay, every frame of an animated film had to contain the entire image. A character crossing a room required the room to be redrawn sixteen times a second, with all the labour and all the instability that implies. Backgrounds shimmered because no two drawings of them were identical, and detail was avoided because detail multiplied the work.
The cel separates what changes from what does not. A background is painted once, in as much detail as the artist can manage, and stays fixed under the camera. Only the moving elements are drawn, and only for the frames in which they move. The saving is enormous and it compounds: elaborate settings become cheaper than plain ones because they are amortised across hundreds of frames.
Registration and the licensing company
The overlay alone is not enough. Sheets must return to exactly the same position under the camera or the image jitters. The complementary innovation, associated with John Randolph Bray, was a system of pegs and matching punched holes that held every sheet in fixed alignment. Bray and Hurd pooled their patents into a licensing company in 1915 and charged studios for the right to work this way.
That licensing regime had consequences beyond technique. Studios that could afford the fees expanded; those that could not either infringed, invented workarounds or closed. The concentration of American animation into a small number of large firms during the 1920s is partly a story about intellectual property.
Eighty years, and then software
The cel determined the look of animation for most of the twentieth century. Layer count was limited because each additional sheet dimmed and yellowed the image beneath it, which is why classical animation tends to work in three or four planes. Ink lines were traced by hand onto the front of the sheet and color applied to the back, creating the crisp outline that reads as traditional animation.
Digital ink and paint retired the physical sheet from feature production around 1990, but not the idea. Every animation and compositing application still organizes work into stacked, independently movable layers held in fixed registration. The 1914 patent describes the interface that artists use today.
Historical context
Hurd filed the celluloid overlay patent in December 1914; Bray held complementary patents, and the two pooled them into a licensing company in 1915.
Importance for the industry
This is the single most consequential production innovation in animation history. It cut labor dramatically, made backgrounds richer, and separated the moving from the static — a division that still structures the work.
Consequences for later productions
The cel defined the look, cost and workflow of animation for roughly eighty years, until digital ink and paint replaced the physical sheet in the 1990s. Licensing fees also concentrated the American industry among firms that could afford them.
Sources consulted
- Origins of American Animation, 1900–1921 Library of Congress
- Animation techniques Encyclopaedia Britannica
Links point to the collections, catalogs and reference works consulted. How sources are chosen and weighted is explained in sources and methodology.