A snooker ball is a colored ball used to play the cue game of snooker. In the past, they were carved of wood, which did not stand up well during multiple games. Today, the balls are cast from man-made resins, then further smoothed and polished by machine
The two most common types of resin used for game balls are phenolic and polyester. Phenolic resin is used in higher-quality balls because it is chip- and scratch-resistant and easily keeps a polish. The balls are created by casting the resin into the desired shape.
Castings are made by heating the liquid resin and pouring it into flexible latex molds. Other times, the liquid latex will be forcibly injected into the mold, which guarantees that no air bubbles will form and that the item will be fully cast. The shape of the molds then determines the steps taken to finish the snooker ball. Some molds are made to cast one ball at a time and peel off like the shell of a hard-boiled egg, while others will cast a "chain" of balls. The balls are then broken apart and further smoothed by machine lathes.
Many resin items are painted and varnished after they have come out of the mold. However, snooker balls often take a beating from being knocked against cues, the table, and each other during the course of a game. For this reason, the liquid resin is often pre-colored so that minor abrasions to the balls won't show up after their creation.
Even though resin is a very precise method of casting, snooker balls will vary slightly in weight. When they are finished, the balls will be weighed and matched into sets of the most similar weights. Saluc, a Belgian company that has produced snooker balls since the 1960s, still has every ball checked by hand before it leaves the factory.
The material used to make snooker balls has had a long evolution. Originally, snooker balls were carved out of wood, which did not always stand up to the wear and tear of play. At roughly the same time, manufacturers were searching for an alternative material with which to produce billiard balls, which were then hand-lathed from cured elephant tusks. A prize was offered to the scientist who could come up with an alternative material, and celluloid was born.
Following the success of celluloid, Bakelite and other plastics were developed, ending with the resins that are still used to create many of the products we use today. Some historians claim that the search for an alternative material for snooker balls was the beginning of the invention of modern plastics.