Wednesday, February 23, 2005

How to care for and clean a CD

CDs are a sensitive media. Finger prints and scratches can make music CDs skip or data CDs unreadable. Most people don't realize that the screen printed side of the CD is actually more important than the shiny side. How many times have you laid a CD down "upside down" to keep from scratching the bottom?

How does a CD work? [an over simplified example that should have pictures] A laser (focused LED actually) is directed at the CD and bounces back to a sensor that reads the light. If the laser does not return it is read as a 0. If the sensor picks up the light it reads as a 1. Everything on the computer is handled by zeros and ones. When a CDs is professionally created the data is literally pressed into hot plastic just like an old record was made. The technology is virtually the same. Tiny indentions in the plastic cause light to be reflected back toward the sensor or, if the indention is not present, away from the sensor. These indentions are how music and data are stored on professionally made CDs. Your home CD burner accomplishes the same thing chemically by causing some areas of the CD to be darker than others.

The labeled side is the reflective surface that the laser uses to bounce back to the sensor. If the label is scratched the laser light can pass through the label and never be reflected back to the sensor giving a 0 where a 1 might be expected. This is a read error. The focus of the laser is actually designed to go beyond the surface of the "bottom" of the CD so that minor scratches don't interfere. In truth, scratches on the bottom of a CD are far less serious than scratches on the label.

To clean a CD a soft cloth or non scratch lense cleaner should be used. The cloth should be sweep from the center of the CD to the edge and never in a circular pattern.

To best take care of your CDs, hold the CDs only by the edges and take them from a case directly to the CD reader and back avoiding the temptation to plot the CD down on a book or your desk. Direct sunlight can also damage and reduce the life of your CD media.


Posted by: djuggler | 11:37 AM |