How to Erase Magnetic Tape
Magnetic tape can be reused over and over, but if the tape is not thoroughly erased before reuse, undesirable artifacts, or traces of the old recording, can remain on the tape and interfere with the new recording. This is particularly noticeable on reel-to-reel tape that is being reused on a different type of machine; sometimes the new eraser heads are not big enough to completely erase the old recording. To ensure maximum quality when reusing a tape, it's a good idea to erase it first with a bulk eraser.
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Instructions
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Procedure
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Set your bulk eraser up, away from any magnetic media. A bulk eraser, also called a "degausser," is a powerful electromagnet that undoes the magnetic encoding on the tape. There are many types, ranging from small handheld devices to large automated factory systems.
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2
Turn your bulk eraser on, and slowly move it along the tape you want to erase. Magnetic media such as tapes and disks store information by using tiny magnets to set the polarity of tiny magnetic particles on the tape. Later, the read head can discern which way the particles are pointing, and reconstruct the original signal. Move the eraser near the tape and then slowly along the length of the tape to reset the particles to a neutral state. If your tape is coiled on a reel, move the eraser in circles around the reel. A cassette tape might be erased in 10-15 seconds. A reel to reel tape might take a little longer.
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Slowly move the eraser away from the tape while it's still on. This helps prevent the tape from acquiring undesirable degaussing artifacts, such as a hissing sound.
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Test your tape by playing it. If any artifacts of the original recording remain, repeat the degaussing process, moving the eraser slower and close to the tape.
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Tips & Warnings
Don't turn your bulk eraser on near any tape or other magnetic media such as computer disks that contains information you want to keep. It will indiscriminately erase any magnetic media in its vicinity.
Some newer magnetic media, such as computer hard drives and some tapes designed for holding digital information (such as some tape used for computer backup), cannot be reused after it has been degaussed. Magnetically encoded head positioning information is recorded on these media at the factory to make them more reliable, but it can't be recreated without very expensive equipment.
Bulk erasing a tape might not completely destroy information on the tape. It is sometimes possible to recover information with sophisticated equipment, even if the tape seems to be blank, but the process is expensive and time-consuming.
