As CD-ROM discs are read by a laser, there is no contact or "wear" while the discs are played. Discs can be damaged during use, but some common sense procedures can guard against this possiblity. The first thing to remember is to always handle discs by their edges. This makes sure that finger prints do not get on the read surface of the disc and cause errors by blocking some of the laser light. Another suggestion is to keep the discs in their package or caddy when not in use. This is done to prevent any scratching that may occur should the discs just be left on a desk or in a "pile" of discs. You may be wondering why scratches would be a problem given the hard plastic construction of the CD-ROM. As we described above, some of the layers that make up the disc are very thin.

A point that many people don't realize is that the side with the label is the most sensitive to scratches! This is where the layers are the thinnest and a scratch can do the most damage. A single scratch of a pencil lead can go through the label, seal coat, metal and actually damage the pit layer below. Of course, scratches on the read side aren't good either, but they are so far out of focus (see laser focus diagram) that they don't usually cause a problem unless they are quite large.

Laser Focus Diagram

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