Isopropyl alcohol
One problem occurs when iron oxide (or similar) particles from the tape itself become lodged in the playback head. As a result, the tape heads will require occasional cleaning to remove such particles. The metal capstan and the rubber pinch roller can become coated with these particles, leading them to pull the tape less precisely over the head; this in turn leads to misalignment of the tape over the head azimuth, producing noticeably unclear high tones, just as if the head itself were out of alignment. Isopropyl alcohol and denatured alcohol are both suitable head-cleaning fluids.