Disc rot is a phrase describing the tendency of CD or DVD or other optical discs to become unreadable due to physical or chemical deterioration. The causes of this effect vary from oxidation of the reflective layer, to physical scuffing and abrasion of disc surfaces or edges, including visible scratches, to other kinds of reactions with contaminants, to ultra-violet light damage and de-bonding of the adhesive used to adhere the layers of the disc together.