What is the reason acetate replaced celluloid in animation?

Acetate replaced celluloid in animation primarily because celluloid is unstable. Celluloid, while widely used in the early days of animation, has several drawbacks, one of the most significant being its tendency to become brittle over time and its susceptibility to deterioration. This instability can lead to issues such as discoloration, warping, and even the potential for flammability, which poses safety concerns.

In contrast, acetate film is much more durable and resistant to these issues. It does not degrade as quickly as celluloid, making it a more practical choice for animators who needed reliable materials that would stand the test of time. As a result, the animation industry transitioned to acetate to ensure the longevity and quality of animated works.