General Science and Technology | How Are Compact Discs (Cds) Made?
How are compact discs (CDs) made?
The master disc for a compact disk (CD) is a flat glass disc coated with a chemical called a "resist." The resist is impervious to (cannot be removed by) a glass-dissolving substance called an "etchant." The master is placed on a spinning turntable, beneath a laser. A digital signal is sent to the laser, turning the laser off and on. When the laser is on, it burns away a small amount of the resist on the disc. The laser creates a spiral track of elongated "burns" in the resist surface.
After the recording is complete, the glass disc is placed in a tub of chemical etchant. The etchant dissolves the glass only where the resist has been burned away. After the etchant bath, the spiral track on the disc consists of a series of small pits of varying length and constant depth, interspersed with areas untouched by the laser, called "lands."
To play a recorded CD, a laser beam scans the...
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