what are bowling balls made of

Bowling balls can be made of different materials, including wood, rubber, plastic, polyester, and resin (reactive urethane) . In the past, most bowling balls were made of a very hard wood called Lignum vitae, but by the early 1900s, rubber was incorporated into its build with balls like the Everture and later the Brunswick Corporation’s Mineralite all using a hard rubber. Polyester balls were introduced in 1959, and by the 1970s, plastic dominated over rubber balls, which then became obsolete with the early-1980s development of polyurethane ("urethane") balls. Nowadays, bowling balls are designed with computers and have carefully crafted and balanced cores that influence how the ball travels down the bowling lane. The coverstock materials used in modern-day bowling balls are polyester, urethane, and resin (reactive urethane) . The process of making a bowling ball involves creating the core, which is placed inside a mold that serves as the coverstock before material is poured into the mold to harden around the core.