For DVD scratches, DVD scratch repair techniques may be required in order to make problem discs playable.
There are several types of DVD scratch removal and these include the use of fillers, polishes, or sanding of the disc. Fillers are substances that are applied to the scratch in order to fill the gouge and essentially make the scratch disappear. In general, this type of scratch repair is not very effective. Another DVD scratch repair method involves using mildly abrasive substances to polish out the scratch. As is the case with fillers, these polishes are usually not very effective.
Very large scratches can be reduced and some playability may be restored to the DVD, but generally additional smaller scratches are produced which can result in additional problems. The third DVD scratch removal method involves sanding the disc. The disc is sanded with fine sand paper down to the level of the scratch and then the disc is polished so that the base is transparent once again. This technique requires specialized equipment and has the greatest chance of success when compared to the other methods. Used DVD or CD stores usually possess this equipment and offer a scratch repair service for a fee.
Although moderate success is possible when using the sanding technique to repair scratched CDs, with DVDs the procedure is riskier. A DVD is two discs, half the thickness of a CD, glued together. For single layer discs, the information layer and metal layer are at the top of the disc, but another “dummy” disc is glued on top. The information and metal layers are therefore protected by 0.6 mm of plastic on either side and the base of the disc is essentially only approximately 0.6 mm thick as compared to about 1.1 mm for CDs. Because of the base thickness differences between a CD and DVD, there is much less plastic to sand away in order to remove a scratch for a DVD disc. Also, small changes in the thickness of the DVD base will affect how the laser light interacts with the disc. Uneven sanding will cause warping and balance issues. For these reasons, the chance of successful DVD scratch repair using this DVD scratch removal method is lower compared to CDs.
The above techniques are for scratch repair of DVD scratches on the base or reading side of the disc. Because the sensitive metal and information layers are in the middle of the DVD disc structure as discussed above, scratches to the top layer will not damage the metal layer. This is different than the CD situation, where these layers are near the top of the disc and top side or label side scratches will irreversibly damage the metal layer. Therefore, for DVDs, scratches to the label side are not a concern.
A final point is that DVDs have seven times more information stored on a disc compared to a CD. Therefore, the same size scratch can potentially damage much more information. DVD technology does employ better error correction than CD technology in other to fix problems, but to be safe, it is best to avoid scratching the disc by handling and storing the DVD properly so that DVD scratch repair with a DVD scratch removal technique will not be required.
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