Development of materials for pressing gramophone records until 1983
The earliest gramophone discs were pressed by Emil Berliner in the USA from ebonite or vulcanised rubber. In 1896, the first record was made from a compound of shellac (a bonding agent) and ground shale (a filler). The expensive and scarce shellac was ultimately replaced by Novolac, a phenol-formaldehyde resin, which was produced for the Czechoslovak gramophone record industry by the Stalinovy závody (Stalin Works) in Litvínov, and used for pressing records in the factory in Loděnice between 1952 and 1954. Gramophone discs were manufactured in Loděnice until 1964. In 1952, a new pressing matter, based on vinyl chloride, started to be developed. In 1957, the composition of the components stabilised, which led to records possessing better acoustic properties – vinyl discs. The subsequent period, until 1983, saw the optimisation of the pressing material, with the resulting copolymer, KV 172, almost reaching the quality of top foreign copolymers. The greatest progress was attained in the homogeneity of batches and the preservation of even parameters between the batches.