Acetate discs (also known as lacquers or instantaneous discs) are a type of phonograph record created using a recording lathe to cut a groove in real-time, rather than mass-produced from moulds.
Unlike standard vinyl phonograph discs, acetates consist of a core material (usually aluminium, but glass and cardboard have also been used) coated with black nitrocellulose lacquer (prior to 1934, cellulose acetate was used as the coating, hence the common but incorrect name of acetate). They have ranged in size from 7-inches to 16-inches. Due to the metal core, acetates are heavier than standard records. Cheaper acetates may have a second hole near the centre, to prevent the disc slipping on lathes that don’t have a vacuum turntable. They are often one-sided, with no grooves on the reverse, and labels may be typed or handwritten rather than printed.
Acetates are used in record manufacturing; a master disc is created by dubbing from another medium (such as a master tape) and electroforming is then used to make negative metal moulds from. They were also used to evaluate the quality of the tape-to-disc transfer, to compare different takes or mixes of a recording, to get approval from band members, or to get preview copies to radio stations before the mass-produced copies were available.
Prior to the availability of magnetic tape, acetate discs were used for direct-to-disc recording. Home recording machines of the 1940s and 1950s used acetates.
Acetates wear much quicker than standard vinyl records due to the softer material used, and a chipped stylus can damage an acetate in one play.