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|CED in the History of Media Technology|
RCA began research in 1971 into fully conductive VideoDiscs in parallel with their research on metallized discs. In 1977, researcher Leonard Fox perfected the method of manufacturing conductive discs by impregnating polyvinyl chloride (PVC) with minute particles of Ketjenblack EC, a form of conductive carbon. This was a simpler, more reliable, and more durable manufacturing method than multilayer discs, and was soon adopted as the manufacturing method for production discs. The carbon black composition of the discs was about 15% by weight, which made the PVC somewhat stiff. Because of this compression molding was adopted in lieu of injection molding for disc manufacture.