While LaserDisc is by and large a robust medium suitable for archival purposes, improper manufacturing is a serious problem. With something so large in relation to the fine detail which is actually played, it is clear that the chances of something going wrong are nonnegligible. Flaws in the stamper, an insufficiently clean environment, malfunctioning pressing equipment, and other causes can make the disc unplayable as it comes from the manufacturer. More insidiously, discs can break down over time if chemical impurities, construction defects, or extremely poor storage [repetitive strong thermal cycling, high humidity, and the like] permit the aluminum data layer to be attacked by oxidizers, altering its optical properties. Some particular discs, and the products of some entire pressing plants, are particularly prone to this type of time-dependent failure, known colloquially as "Laser Rot". If a disc is listed under this head, purchassing it sealed or sight unseen without an ironclad guarantee is disrecommended.