Scratches on a CD

Here's something I discovered some time ago and promptly chucked aside till today:

When a CD is scratched on the data side(side without label), chances are, it can be saved. However, scratch it on the label side and you probably end up with a new coaster (CD can't be saved).

For most of us, that somehow doesn't seem too right.

When I put my CDs down, I nearly always tend to put it label facing down but alas, that's not the correct way! Instead, if you want to protect ur CD, it's always better to put the CD such that the data side faces down.

Here's an explanation:

In CDs, the reflective and data layers are just below the label and a thin sheet of polycarbonate substrate. A much thicker layer of the substrate supports and protects the bottom of the disc.

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While not all scratches on the data side can be salvaged, small scratches do little to affect data reading as the laser reads the data layer of the CD through the substrate. Big scratches might affect data reading though often, error detection and correction can minimise such problems from occuring.

However, one must note that when the scratches on the data side is so deep that it cuts into the data layer itself, the CD will be a goner.

Because of this same reason, since the data layer of the CD on the label side is protected only by a thin sheet of substrate compared to the data side, the former is a lot more sensitive to scratches. As such, even a small scratch on the label side could result in the data layer being destroyed and hence making the CD un-readable!

For those who needs more proof, try taking two unwanted CDs and test out this idea. Scratch one CD on the data side and the other on the label side. Most likely the one with a scratch on the data side would still be able to play while the one scratched on the label side would not.

For more info, click here, here, and here.