As the playing of gramophone records causes gradual degradation of the recording, they are best preserved by transferring them onto other media and playing the records as rarely as possible. They need to be stored on edge, and do best under environmental conditions that most humans would find comfortable. The medium needs to be kept clean, but alcohol should only be used on PVC or optical media, not on 78s.[citation needed] The equipment for playback of certain formats (e.g., 16 and 78 rpm) is manufactured only in small quantities, leading to increased difficulty in finding equipment to play the recordings.