What materials were 45 rpm records made of?
Unwilling to accept and license Columbia's system, in February 1949 RCA Victor, in cooperation of its parent, the Radio Corporation of America, released the first 45 rpm single, 7 inches in diameter with a large center hole. The 45 rpm player included a changing mechanism that allowed multiple disks to be stacked, much as a conventional changer handled 78s. The short playing time of a single 45 rpm side meant that long works, such as symphonies, had to be released on multiple 45s instead of a single LP, but RCA claimed that the new high-speed changer rendered side breaks so brief as to be inaudible or inconsequential. Early 45 rpm records were made from either vinyl or polystyrene. They had a playing time of eight minutes.