Some cassettes will stand up to erasure and reuse. Follow these steps with a handheld eraser to do a thorough job.
Completely rewind tapes before starting procedure.
The cassette is now demagnetized, or erased, and ready for reuse.This entire procedure can be done in less than five seconds per cassette.
Stationary tabletop cassette erasers have an on/off cycle time which will vary. These times range from one minute on to between 3 and 15 minutes off, depending on the unit's output power.
Be careful not to perform these erasing techniques too close to your store of recorded tapes the magnetic field of these machine can damage the audio content of nearby tapes.