The replication process for DVD is essentially the same as that for CD, except with much closer tolerances and some extra steps. There are also some differences in replication depending on the type of DVD disc being made: DVD-5, DVD-9, DVD-10 or DVD-18.
All DVD discs are made of two parts, each half the thickness of a CD; that is, each part is 0.6 mm thick. The two parts are bonded together, producing a disc as thick as a CD (1.2mm). Thus, two pressings are needed to make one complete disc. DVD-5 and DVD-9 discs, which have data on only one side, consist of one part with data and one blank part.
As in CD replication, DVD replication begins with a flat glass disk covered with photo-resist material. As the disc spins, a laser beam modulated according to the information on the DLT tape "writes" the data onto the disc by creating chemically-etched pits. Family names are often used to describe the next steps in the process. By electroplating, a metal negative to the glass disc is produced; the metal disc is called the "Father." Again by electroplating, a positive-image "Mother" disc may be made from the Father stamper, and negative-image "Sons" are plated from each Mother.
The Father and the Sons are then placed in molding presses. Melted plastic is poured over the Father and Sons and allowed to cool. (As compared with a CD, DVD discs need a shorter plastic-injection time and a higher molding temperature.) The disc is then finished by applying a reflective layer, protective lacquer, and labeling.
DVD-9 and DVD-18 discs contain data in two layers; one of the layers is semi-reflective, allowing the playback laser to read the data on both layers in sequence. Both layers are read by a laser from the same side.