Exploring

Inherent Vice: Early Sound Recordings

Discs

Disc recordings made from a variety of materials were produced and used throughout the late 19th and early 20th centuries. Acetate discs were primarily used for making recordings, while other types were used for pre-made commercial recordings.

The following information is summarized from Gilles St. Laurent's The Care and Handling of Recorded Sound Materials, which should be consulted for additional information.

Acetate Discs

Acetate discs are very unstable due to their coating of nitrocellulose lacquer plasticized with castor oil. The plasticizer gradually evaporates off, causing the lacquer coating to become brittle and shrink. This coating is bonded to a base (usually aluminum) that cannot shrink, so the coating cracks and peels off the base. Acetate discs are also subject to chemical reactions that result in the formation of acids, which further accelerate deterioration. As with other materials, these chemical reactions are made worse by high temperature and humidity.

Vulcanite Discs

These were made from vulcanized rubber (vulcanization made the rubber stronger and more elastic) and were first marketed by Berliner in the 1890s. Vulcanite discs are quite stable when stored in the dark, but very unstable when exposed to light and/or heat and humidity. Light facilitates the oxidation of the rubber, forming sulphur oxides and sulphuric acid in the presence of humidity. This acidity eventually causes the plastic to decompose.

Vulcanite discs also have characteristic problems such as warping, blisters, and particles that are a result of the production process.

Shellac Discs

Shellac discs were first introduced in the early 1900s. Early discs were made with an organic shellac binder (produced from insect secretions) that covered a core. Later shellac discs were made from a plastic resin that was slightly more stable. Cores were made from many types of fillers with a wide range of quality (e.g., powdered limestone or slate, carbon black, lubricants, oils, resins). Therefore, making generalizations about the causes of deterioration is difficult.

Shellac discs are relatively stable, but are prone to slow embrittlement of the shellac coating. The curing process during the manufacture of shellac discs causes chemical reactions that eliminate water or ammonia molecules, causing embrittlement. This process continues, although more slowly, throughout the lifetime of the disc, and it is accelerated by high temperature and humidity.

Edison Diamond Discs

In 1911, the Edison Company began marketing a new disc made from a synthetic plastic called phenol. This plastic material formed the core of the disc, which was then coated with thin layers of varnish. These discs were quite stable and not prone to warping like others. However, prolonged contact with moisture or high humidity may damage them. These discs were designed to be played on Edison phonographs only and they were incompatible with other players., While they enjoyed significant popularity for some time, they were eventually supplanted by other types of discs. By 1929, they were no longer being produced.

Vinyl Discs

Vinyl discs were first introduced in 1930, but did not become popular until the late 1940s, when both 331/3 rpm long play vinyl records and the 45 rpm format were introduced. Vinyl discs are quite stable, even though they are made from polyvinyl chloride (PVC), which deteriorates upon exposure to light or heat. The deterioration process produces hydrochloric acid, which further accelerates the corrosion. To control this, a stabilizing chemical that consumes the hydrochloric acid is added during the manufacturing process. This generally provides enough protection for several decades.