Cleaning dirty CDs and DVDs

I see a lot of dirty DVDs after video rental stores. Well, here is the procedure that I learned from searching from the net. Cleaning CDs and DVDs should be done with a cleaning kit but can also be done with a normal clean cotton cloth or shirt. When doing this with a clean cotton cloth or shirt, wipe against the tracks, starting from the middle of the CD or DVD and wiping towards the outer side as shown in the below picture. Never wipe with the tracks--- by doing it may put more scratches on the disc. It is recommended to use water when cleaning a CD and if the substance on a CD cannot be removed using water, use pure alcohol to clean.