RE: Magnetized tapes

Schmitt, Mike (schmittm@uwgb.edu)
Fri, 29 Dec 2000 13:27:21 -0800 (PST)

It takes a much stronger magnetic field to erase videotapes. In the case of
digital and SVHS video even conventional tape erasers don't have much effect
on the recorded data.

Audiotapes, on the other hand, are more likely to be damaged by stray
magnetism. The wand could be erasing part of the data. Also, audiotapes
are likely to degrade in quality over long periods of time when stored
inproperly like in hot cars. Dirty heads, dirt on the tape itself,
humidity, etc., all play their part.

--Mike Schmitt
A/V Services
UW-Green Bay

-----Original Message-----
From: Paul Duckworth [mailto:pauld@mail.orion.org]
Sent: Friday, December 29, 2000 2:01 PM
To: Multiple recipients of list
Subject: Magnetized tapes

This is a question about audio tapes, not video. Many people on this
list deal with spoken audio as well as video, so I'm hoping someone can
help with this mystery.

My library is finding many audiobooks on cassette being damaged by some
unknown source of magnetism. This results in the sound fading in and
out. I am almost 100% sure that it is happening due to staff error. We
use magnetizing wands to activate the security strips in books and do
this by moving the wand along the spines of carts of books ready to be
re-shelved. I am guessing that occasionally an audiobook gets stuck in
with the books and gets exposed to the magnetism by a staff person who
isn't paying attention. But... I'm not finding any damage to
videocassettes from magnetization.

Questions:
1. Is there another likely source of magnetization that users of
audiobooks could be exposing our tapes to?
2. If a videotape were exposed to magnetization, what would be the
expected damage? just to sound or also to image quality?

Thanks, Paul

Paul Duckworth
Collection Development Coordinator
Springfield-Greene County Library District (Missouri)