What immediate application drove the commercial success of Hyatt's Celluloid material?

As a replacement for ivory, most famously used in billiard balls.

John Wesley Hyatt's contribution was transforming the semi-synthetic Parkesine into Celluloid, the first plastic to achieve significant commercial success. The primary market demand that Celluloid successfully met stemmed from the scarcity and high cost of natural ivory. Ivory was traditionally used for high-value goods, including the production of high-quality billiard balls. By creating a stable, reliable, and manufacturable compound based on modified cellulose, Hyatt successfully substituted this expensive natural commodity. This application demonstrated plastic's potential to move beyond laboratory curiosities into tangible industrial commodity production, thereby proving its economic viability.