The process of producing the stampers required for pressing vinyl records involves several steps via either the newer DMM or older lacquer processing technologies. The final result of the two technologies is the stamper, which is formed and prepared for pressing.
DMM plates processing
In 1985, GZ implemented the DMM (Direct Metal Mastering) technology founded by the German company Teldec. This technology involves the production of steel plates which are coated by a layer of copper through a special galvanic process. The advantage of manufacturing our own copper plates is the possibility to control their quality and adapt the number of plates produced according to the pressing requirements. After cutting the audio grooves into the copper layer (see page Mastering) and engraving them with information necessary for identification, the plates are then immersed as a cathode in an electroforming bath. An electric current flowing throughout the bath from the nickel anode to the cathode creates a deposit of nickel atoms onto the copper layer. We then get a mirrored image (negative) of the plate after separating the accrued nickel layer, therefore yielding an unformed stamper. DMM technology allows for several sonically accurate stampers to be directly produced from 1 DMM plate.
The traditional technology of pressing records from lacquers typically requires a triple electroforming process - which is complicated and expensive. The lacquers are silvered and act as a cathode immersed in an electroforming bath. An electric current flowing throughout the bath from the nickel anode to the cathode creates a separable layer of metallic nickel called the father, which is a mirror image of the lacquer. Another electroforming process is needed using the father to create a second nickel layer – which is called the mother. The mother is the positive and can reproduce the sound in the grooves. It is therefore possible to play the mother on a turntable to check the quality after the electroforming process. In the third process, the mother is used to produce a nickel stamper. The father and mother may be used for making new stampers again, but the original lacquer can only be processed once.
Preparation of stampers
An unformed stamper is the result of the electroforming process after either of the technologies (DMM or lacquer) implemented. After the stamper is produced, it is necessary to prepare it for the pressing machines. This process is carried out in several steps. The back side of the stamper is grinded and smoothed. Afterwards, it needs to be precisely centred (according to the sound grooves) before the central hole is cut. The edges of the stamper are trimmed and the area around central hole is resurfaced. Afterwards, the edges of the stamper are formed and adapted for mounting on to the pressing moulds.