The disc on which the source data (from either PCM-1630 tape, Exabyte tape or CD-R) is imprinted as the first step in CD replication (mastering). The glass master is a glass plate, about 10” in diameter, coated with a light-sensitive material (photoresist). During mastering, the source signals are converted to the EFM coding format for the CD and fed to the special laser beam recorder (LBR) which etches very tiny pits on the material. The glass master is very delicate, and cannot be played. Succeeding steps in the process, called the “ father”, “ mother” and stamper, result in the metal forms which are capable of hot molding thousands of compact discs on the presses.