Master disc  --  Lacquer-coated aluminium disc 14 inches in diameter for a 12 inch record and 10 inches for a 7 inch. When completed, the lacquer disc is coated with silver to make it conductive for electroplating with nickel. This is done in two stages: a slow, precise coating to plate the grooves with 1 mil of nickel, followed by a faster build-up of 20- 30 mils. The nickel is then parted from the lacquer to form a negative metal master disc having ridges in place of grooves. Although this could be used to stamp out the final pressings, it is much too fragile. The next phase is to produce the mothers.