February 1996
CD's can get scratched to a point where the optics are affected by the surface of the CD. Actually, the plastic is a "protective" coating for the aluminum inside. Usually minor scratches on CDs can be removed if you are very careful. One way is to use a soft cotton ball and clean the CD. If that doesn't work, you can get an acrylic polish (Prist Acrylic, Plastic and Glass Cleaner (spray) PPG L555-A1-387A, Prist Plastic Polish (liquid), Fed Spec PP-560B) PPG -555B-1A-1187A or Micro-mesh Scratch Removal and Restoration Kit KR-70). Work from the center of the CD to the outside in straight lines. Don't work in circles!! The Prist and Micro-mesh products are intended for acrylic airplane canopies and you can get them through most private airplane distributors service department or independents. My dad was a fighter pilot and I used to get this at the airport supply stores.
Practice on an "expendable" CD first. Getting used to using polishes can be a bit tricky and you need to acquire the "touch" before you attempt this on a valuable part of your music collection.
BUNDEE International also markets a CD/Laser Disc Repair and Protection System which I've used on my Laser Discs with no problem but I haven't needed to try the stuff on CDs. Whatever you do, DON'T use any abrasive cleaners or cleaners with petroleum solvents, ammonia or other harsh cleaning agents on a CD. If you do, you will probably damage it to the point it can't be repaired.
Don't use any of the CD cleaning machines as they clean in circular patterns and can actually do more harm than good - especially if there's dirt or debris on the CD.
Use the acrylic liquid cleaner (e.g. Prist) and follow the instructions remembering to only clean from the center to the outside of the CD in single pass wiping motion. Don't spend any amount of time in one spot as the small amount of heat this can generate can distort the thin data metallization of the aluminum film inside. Then you may rinse the CD and dry it by using a dry soft towel. Don't wipe the CD!! Just pad it dry. Then, put it into the CD player so that it will spin and let it run that way for at least 20 minutes so that any moisture in the disc sandwich gets spun out. There won't be enough moisture to do damage to your player.
Try the above treatment for minor scratches first. If that doesn't work and your CD is not playable, you already have nothing to lose so you may then proceed with this step. Be extremely careful if you attempt this process!!!!! Practice on an expendable CD first as this method is not easy.
Use the Micro-mesh kit. Follow its instructions which tell you to vary the direction of rubbing and polishing. With each grit, always begin rubbing with the circular direction but end rubbing radially (center to outside). Make sure you always end each step working to the outside from the center!!! Only work on the area which is damaged. After each grit, go to a finer polish and slightly overlap the preceding area. Keep doing this until you have finished using the finest polish. Don't ever apply a lot of force or push down hard on the CD. Don't work for a long time in one area. The polishing process generates heat which can destroy the disc permanently. When you are through, the disc should look as smooth as glass when held so as to see clear reflections. You may, if required, follow up with the steps above. It helps if you have a hard and very flat surface to work on. Put an unfolded towel down so the CD won't slide around as you work.
Warped CDs can be flattened again by placing them between two pieces of plate glass and pressing them for a long time. Since CDs are made out of plastic, they can warp if they get too hot. First warm the disc to about 100 degrees F. Make sure the disk is clean of any and all debris! Again, use a soft material and clean the disc radially (center -> outside). When the disc is at a warm temperature, place it between the two sheets of plate glass and then weight the glass-disc-glass sandwich with about 10 pounds of books. Make sure that the weight is centered directly above the hole in the CD. Leave it that way for at least 2 or 3 days.
If the disc suffers from "laser rot", you should demand from the manufacturer a replacement disk. "laser rot" is rare on CDs but is common on older Laser Discs. Laser rot is the result of "out gassing" from the vinyl to the aluminum which results in excessive oxidation of the aluminum media material. It is visible and is definitely a manufacturer defect due to a flaw in their processing.
If a disc is cracked, it may be playable - at least the first tracks as CDs play from the inside to the outside. The problem is that they spin at a very high rate of speed and pieces may fly off and permanently damage your CD player. If you have a cracked CD, I recommend that you throw it away and acquire a new one.