When you played billiards during the early days of plastic, you took your life into your hands. Under the right circumstances, your bank shot could cause a ball to explode. 

Billiards played an important role in driving the development of synthetic plastic. In the Victorian era, billiard balls were made of ivory, a material created from carved tusks. But some feared (perhaps erroneously) that ivory’s popularity was going to lead to a shortage of the material, as elephants would be hunted to near extinction. They were onto something—but it wouldn't happen for decades

Phelan and Collender, a major billiard table manufacturer, offered a $10,000 reward to any person who could make a non-ivory billiard ball. In 1869, an inventor named John Wesley Hyatt came up with a solution. He mixed nitrocellulose with alcohol and a waxy resin called camphor, and molded it into a ball that looked and felt a lot like ivory. This material, patented as Celluloid and later used for artificial dental plates, was the first mass-market synthetic plastic, launching what became known as the Age of Plastics

Unfortunately, nitrocellulose is also called guncotton, and it’s combustible. It explodes so rapidly that it doesn’t typically set anything on fire, but it can burst into flame and make a loud bang. And in boozy 19th-century pool halls, that was not such a great idea. As Hyatt wrote in 1914:

In order to secure strength and beauty, only coloring pigments were added, and in the least quantity, consequently a lighted cigar applied would at once result in a serious flame, and occasionally the violent contact of the balls would produce a mild explosion like a percussion guncap. We had a letter from a billiard saloon proprietor in Colorado, mentioning this fact and saying he did not care so much about it, but that instantly every man in the room pulled his gun.

The clack of billiard balls rolling together can be a satisfying sound during a game well played. A small flash-bang going off in a dark, smoky billiard hall is another thing entirely. Just hope there was no hustling going on when the guns came out. 

[h/t: io9]