Compact Disc RECORDABLE (CD-R) Picture courtesy of Maxell Inc CD-R's are recordable compact discs.  The main advantages to CD-R's are their high storage capacity for video, audio and data, and the ability of the CD-R to be read by both and audio CD-player and a CD-ROM drive.  The disadvantage to CD-R's is that once data is recorded, it cannot be erased or rewritten.

Compact Disc REWRITABLE (CD-RW) Picture Courtesy of Maxell Inc CD-RW's  are re-writable compact discs.  The major advantage of these discs is their ability to be erased and re-recorded.  The number of times the disc can be rewritten depends upon the quality of the disc.  The disadvantage is that not all CD-ROM drives can read CD-RW's.

How they work...
CD-R 
These are very similar to CD-ROM, but there are some key  differences:

• Use the same wavelength laser but at higher strength
• Use a spiral groove that is molded into the surface to guide the laser
• Not pressed like a CD-ROM
• Laser is focused on the disc and heats an organic dye (instead of photo resist)
• Heated organic dye is where the term "burned" comes from
• "Burned"/ "not burned" areas become land and pits

TIPS FOR CD-RECORDING:Picture from PCTechguide

•  Do not touch the recording surface
•  Keep the surface clean, but DO NOT clean with a cloth, unless it is a CD cleaner cloth
•  If cleaned with CD cleaner cloth always wipe radially, NEVER wipe circularly around disk
•  Sudden temperature/ humidity changes may cause disk to warp
•  Only write on CD with felt- tipped pen- DO NOT attempt to erase
•  Do not use stickers or labels on CD

• Similar to CD-Rs: polycarbonate layer with spiral groove to guide laser
• Recording layer is sandwiched between dielectric layers
• Instead of dye based recording, RW discs use crystalline compound (mixture of Silver, Indium, Antimony, and Tellurium)
• When the mixture is heated then cooled, it forms a crystalline, but if heated to a higher temperature and cooled, it forms an amorphous(non-crystalline)
• The crystalline layers reflect the laser and the non-crystalline layers absorb the laser and shrink to form the pit

• 3 Different Laser Powers:

           2. Erase Power: medium power, melts recording layer all back to crystalline

           3. Read Power: lowest power, does not alter the mix- reads CD

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Last edited on May 14, 2000