glass master

The process of manufacturing a CD where discs are created through injection molding polycarbonate plastic.  These 'green discs' are then aluminum plated and another 'top coat' of plastic is applied for the label.  Generally, a batch of one thousand discs is the smallest quantity that a replication plant can cost-effectively offer.  This process yields a very high-quality, professional product, and is not to be confused with duplication which is of lesser quality.

A glass master is made at the replication plant in a specialized clean room, not at the mastering studio.  A glass disc, 240mm in diameter and 6mm thick,  is used as a substrate to 'etch' the image of the digital data as pits and lands that will ultimately be the ones and zeroes that the CD player will read as audio information.  Some audiophiles insist on real-time (1x) creation of a glass master for highest audio quality.