Plastic was invented in the 19th century and was originally used to replace common materials such as ivory, rubber, and shellac.[4] Plastic bottles were first used commercially in 1947 but remained relatively expensive until the early 1950s when high-density polyethylene was introduced.[5] They quickly became popular with both manufacturers and customers because of their lightweight nature, relatively low production, and transportation costs compared to glass bottles.[6][7][8] However, the biggest advantage plastic bottles have over their glass counterparts is their superior resistance to breakage, in both production and transportation.