Swindon U.K.

Stamper Production

The cleaned Glass Master is sprayed with silver nitrate and a reducing solution to create a thin coat of silver. It is then electro-plated with high grade nickel in a two stage process. This gives the metal form rigidity, and it can then be removed from the Glass Master. This is the Metal Master, a negative image.

After careful cleaning the Metal Master is used to ‘grow’ positive masters, or Mothers. This is another electro-forming process. A number of mothers can be made from one Metal Master.

Again after careful cleaning the positive Mother is used to create the Stampers – the final negative image from which the videodiscs are pressed.

Disc Pressing

A pair of Stampers (Side 1 and Side 2) are placed in the press. The electro-conductive plastic compound from which the disc is made is extruded in a semi-liquid state into a carefully regulated form, known as a Patty. This is transferred to the space between the stampers, and as the press closes. steam is injected.

When the Patty has spread out cold water replaces the steam — the compound solidifies, and a videodisc emerges.

The disc is edge-trimmed, proceeds through quality assurance, and is then placed into its protective plastic disc case.

The VHD Videodisc is housed in a plastic case. The VHD player removes the disc when the case is inserted and replaces it after use.

Author: Thorn EMI Videodisc

Thorn EMI was formed in 1979 from the merger of Thorn Electrical Industries, manufacturers of lightbulbs, radios and televisions, and Electric and Musical Industries, with interests in film distribution, television and music. The two demerged in 1996.

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