Technology In-Depth


What Is CD-Recordable Media?

CD-Recordable discs come in many different colors. They consist of a layer of polycarbonate substrate, a layer of dye (which gives the disc its color), and a reflective metal layer of gold, silver, or other alloy. A protective lacquer overcoat helps protect against scratches. The drive or burner writes to a CD-R disc by focusing a high-powered laser on the dye layer, which heats and alters the surface to create a low reflection (Pit) or high reflection (Land).

CD-RW media is constructed a bit differently. Instead of a dye, the recording layer is an alloy, which changes from a transparent crystalline structure (when new or after erasing) to a light-blocking amorphous state. The reflective/non-reflective lands and pits are read in the same manner as the CD-R media.

Unlike standard CD-R media (write once, read many times), CD-RW media can be erased and reused up to 1,000 times. Drives labeled with the logo "MultiRead", support the reading of erasable media.

Refer to your optical drive manufacturer's Media Compatibility List for each the media that is compatible with your optical drive. Verify the write speed (e.g. 1X-24X.) and disc length (e.g. 74-minute or 80-minute media). The specified media is certified for your recorder at the listed write speed. This is especially important for CD-RW discs, which are rated for specific record speeds: "Low Speed" (1X-2X), "Normal Speed" (2X-4X), and "High Speed" (4X-12X) or higher. CD-RW discs cannot be written faster than the disc is rated for, regardless of the top speed of the drive. Each drive that supports "High Speed" media carries the "High Speed" logo on the front of the drive bezel. Note that a Normal Speed 4X CD-RW drive is not compatible with High Speed Media, so it is a good idea to write down what your driver supports and keep it for media purchases. For example, a Plextor PX-W12432Ti/e SCSI and the PX-W8432Ti ATAPI were developed prior to the introduction of High Speed media, and only support "Low Speed" (1X-2X) and "Normal Speed" (1X-4X) media.

Some manufacturer's firmware upgrades include added support for new write strategies for newer media or new media manufacturers. For a current information about recommended media, or firmware upgrades for your drive, consult your optical drive's manufacturer's website.

Some things to be aware of

Some CD readers (Home/Auto/older CD-ROMS) may not read one brand/type of CD-R or CD-RW media, but will be able to read others successfully. This is typical of CD-ROM drives manufactured before 1998. Advances in drive technology and the introduction of the MultiRead specification from OSTA (Optical Storage Technology Association), ensure disc compatibility with most CD-ROM drives. For CD-ROM drives that display the "MultiRead" logo on the drive bezel, you can be sure that these drives read CD-R and CD-RW media. However, displaying this logo is not mandatory, so many newer CD-ROM drives that don't display this logo probably will work just fine (especially true of combinational CD/DVD burners). For Home/Auto/CD players, be sure that the player indicates that it supports the reading of CD-R media. Some players will only read 'stamped' media, that is, commercially available discs.

Taking care of recordable media

It is important to know that recordable media is more fragile than pre-recorded media.

Exposing discs to excessive heat or direct sunlight can reduce the life of the media or even damage/erase it. Keep them cool, clean and store them in a dark place. Use a soft-tipped pen with water-soluble non-toxic ink (e.g. Sanford Sharpie line), when writing on the media. The top protective lacquer layer is delicate and may scratch if a ballpoint pen is used, or degrade if an alcohol-solvent marking pen is used. Either problem can result in the loss of your data.
If you need to clean fingerprints or dust from the media, wipe softly with a clean cloth in a radial direction (from center to outside), not in a circular direction.

Tags: CD Recordable Media, CD-R, CD-RW, CD Recorder, CD Optical Drive