Compact Disc-Recordable (CD-R) (1992 – ) | Museum of Obsolete Media (original) (raw)

Compact Disc-Recordable (CD-R) is an optical disc format designed by Philips and Sony, and based on the Compact Disc. CD recorders became available in 1992 but were extremely expensive and it wasn’t until 1995 that they fell below $1000 (around £650).

CD-R discs can be used for audio or data recording, but only CD-R Audio discs can be used in standalone consumer audio recorders.

CD-Rs are a Write Once Read Many (WORM) medium, although the whole disk does not have to entirely written in the same session. Their specification is taken from the Orange Book standards. Properly written CD-Rs are fully compatible with audio (CD-DA) and data (CD-ROM) Compact Disc standards.

Standard CD-Rs are 120mm in diameter (although 8cm mini CD-Rs are also available) and most can store between 74 and 80 minutes of audio or 650 MB to 700 MB of data. Some CD-Rs have an even higher capacity, such as 90 or 99 minutes of audio or an 80o MB to 870 MB data capacity, but anything over 700 MB means they are not fully compatible with CD standards and they may need compatible hardware or software.

A CD recorder writes data to a CD-R disc by pulsing its laser to heat areas of the organic dye layer. The writing process does not produce indentations (pits) – instead, the heat permanently changes the optical properties of the dye, changing the reflectivity of those areas. Various dyes have been used over the years, with cyanine being the earliest and less stable and phthalocyanine being the most stable).

In general CD-Rs are expected to have an average life expectancy of 10 years. As well as degradation of the dye, failure of a CD-R can be due to the reflective surface. While silver is more widely used, it is more prone to oxidation (laser rot). Gold CD-Rs do not suffer from this problem, but are more expensive.

Figures

Dimensions: 120 mm × 1.2 mm

Sources / Resources

• r o x i o | The History of CD-R [archived]
• Fast Guide to CD/DVD – Reference from WhatIs.com
• CD-R – Wikipedia

Preservation / Migration

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