An acetate disc, also known as a test acetate, dubplate (a term from Jamaican reggae culture, now also applied to individually recorded discs of solid plastic), lacquer (a technically correct term preferred by engineers in the recording industry), transcription disc (a special recording intended for, or made from, a radio broadcast) or instantaneous disc (because it can be played immediately after recording without any further processing), is a type of gramophone record, a mechanical sound storage medium, widely used from the 1930s to the late 1950s for recording and broadcast purposes and still in limited use today.
Unlike ordinary vinyl records, which are quickly formed from lumps of plastic by a mass-production molding process, a so-called acetate disc is created by using a recording lathe to cut a sound-modulated groove into the surface of a special lacquer-coated blank disc, a real-time operation requiring expensive, delicate equipment and expert skill for good results. They are made for special purposes, almost never for sale to the general public. They can be played on any normal phonograph but will be degraded by wear much more quickly than vinyl. Some acetates are highly prized for their rarity, especially when they contain unpublished material.
Acetates are typically produced by dubbing from a master tape recording. By electroplating the acetate master, stampers (special moulds) can be created, which in turn are used to press large quantities of regular vinyl records. Acetates are also used for testing the quality of the tape-to-disc transfer. Historically, they were also a favored medium for use in comparing different takes or mixes, and for getting preview copies of impending new releases into the hands of important disc jockeys.
 Physical characteristics
Although once produced in a wide range of sizes (from less than 7 to more than 16 inches in diameter) and sometimes with glass core discs, the examples most commonly encountered today are 10 or 12 inches in diameter and consist of an aluminum core disc coated with black nitrocellulose lacquer. Blank discs were traditionally produced in several different grades, with the best and costliest grade featuring the sturdiest core, the thickest coating and the most perfectly flawless mirror-like surfaces. These top-quality blanks were intended for cutting the master discs that would be electroplated to create stampers (negative metal molds) for pressing ordinary records. Second-quality blanks were considered adequate for non-critical uses such as tests and demo discs. Lower-grade blanks were formerly made for home use by amateurs and may be very thin and flexible, may have a cardboard rather than a metal or glass base, and may have noticeably dull or slightly orange-peel-textured surfaces. Regardless of grade, there is almost always at least one extra "pilot hole" in the label area, meant to be engaged by a special pin which prevents the disc from slipping on the turntable during the recording process. Pilot holes are often hidden by labels applied after the recording was made, but can usually be detected by careful inspection of the label or by holding the disc up to a light bright enough to penetrate the labels.
Acetates have not always been used solely as a means of checking the quality of a disc recording. They were widely used before magnetic tape was invented and in the modern era they are used by dance music DJs (acetates were also used extensively in Jamaica by sound system operators in the late 1940s - 50s.). Because of their limited useful lifetime, acetates were often used as "demos" of new recordings by artists and record labels.
From the 1930s to the late 1940s, before the introduction of magnetic tape, recordings were normally made directly to acetate discs (see direct to disc recording). Acetates were also used as a storage medium for radio commercials; since commercials only run for a limited time, it didn't matter if the disc wore out relatively quickly. During the early tape era (1950s, primarily), acetate discs and portable disc recorders competed with magnetic tape as a location-recording medium, both for broadcast and semi-pro use. Acetate discs inherently are less durable than magnetic tape, and have the disadvantage of not being physically editable—unlike tape, they can't be cut and spliced.
 Gramophone disc mastering
In preparation for a record pressing, acetates are used for quality control prior to the production of the stampers, from which retail copies of the record will be pressed. The purpose of the test acetate(s) in the mastering process is to allow the artist, producer, engineer, and other interested parties to check the quality of the tape-to-disc recording process and make any necessary changes to ensure that the audio fidelity of the master disc will be as close as possible to that of the original master tape. The actual stampers can be made either from normal acetates, or from a DMM disc (see Direct Metal Mastering).
 Dance music
In the dance music world, DJs cut new or otherwise special tracks on acetates, in order to test crowd response and find potential hits. This practice started as early as in the 1960s in Jamaica, between so-called sound systems, as a way of competing and drawing bigger crowds. These discs are known as dubplates. But the word dubplate can interchangeably mean an actual disc or just the music/recording, which can be on any other medium (e.g. CD). Dubplates were used by reggae soundsystems worldwide, and later adopted by producers of various dance music genres, most notably drum and bass and dubstep. Trading dubplates between different DJs is an important part of DJ culture. Actual acetate dubplates are declining in popularity, and being increasingly replaced by CDs and vinyl emulation software because of weight, durability and overall cost.
 Material and packaging
Despite their name, most acetate discs do not contain any acetate. Instead, most are an aluminum disc with a coating of nitrocellulose lacquer. (Glass was also used for the substrate during World War II, when aluminum was in short supply.) This production process results in a disc that is different in many ways from the vinyl records sold to customers at retail. Whereas vinyl records are light and semi-flexible, acetates are rigid and somewhat heavier. More significantly, the thin coating of lacquer on an acetate is much more susceptible to wear; the playback head of a stylus quickly damages the grooves of the record such that after only a relatively few number of plays the audio quality is noticeably degraded. This is not necessarily a problem, however, since acetates are meant primarily for test recordings. Collectors, of course, may find themselves wishing for greater durability.
Acetates typically come in two sizes: 10" discs for singles and 12" discs for albums. The record's sleeve is typically nothing more than a generic cover from the manufacturing company and the disc's label is similarly plain, containing only basic information about the content (title, artist, playing time, etc.), which is usually typed but is often just hand-written.
Due to their rarity, some acetates can command high prices at auction. Brian Epstein's collection of Beatles acetates fetched between $1,000 and $10,000 per disc. An acetate from The Velvet Underground, containing music that would later appear on their first album, The Velvet Underground & Nico, sold on eBay in 2006 for $25,200. An acetate of Elvis Presleys' That All Right recently sold for $82,393.60.
 See also
- Fonopost A service offering recordings by mail using acetate discs.
- "Preserving Sound Recordings". 2005-04-28. Archived from the original on 16 April 2008. Retrieved 2008-04-16.
- "What is an "Acetate"??". 2005-09-15. Archived from the original on 17 April 2008. Retrieved 2008-04-16.
- Documenting Early Radio: A Review of Existing Pre-1932 Radio Recordings, Elizabeth McLeod, 1988-9
- "She's Leaving Home acetate". 2000-02-12. Archived from the original on 11 April 2008. Retrieved 2008-04-16.
- "Beatles recording fetches $10,000". BBC News. 2001-11-18. Retrieved 2008-04-16.
- eBay - VELVET UNDERGROUND & NICO 1966 Acetate LP ANDY WARHOL, Second auction, ended December 16, 2006 (auction details).