They are made mainly of polyvinyl chloride. No systematic stability problems on a great scale have arisen so far, but their stability in the long term, thinking in centuries, is unknown. Humidity , as with all other data carriers, is a most dangerous factor. While shellac and vinyl discs are less prone to hydrolytic instability, most kinds of instantaneous discs are extremely endangered by hydrolysis. Otherwise, as with other carriers, the temperature determines the speed of chemical reactions like hydrolysis and should, therefore, be kept reasonably low and, most importantly, stable to avoid unnecessary dimensional changes.
Mechanical integrity is of the greatest importance for mechanical carriers.
It is imperative that scratches and other deformation caused by careless operation of replay equipment are avoided. The groove that carries the recorded information must be kept in an undistorted condition. Only specialist personnel should, therefore, be allowed to handle and replay mechanical carriers. While shellac discs are very fragile, instantaneous and vinyl discs are more likely to be bent by improper storage. Generally, all mechanical discs should be shelved vertically.