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Subject: Risk to magnetic media

Risk to magnetic media

From: Jim Lindner <vidipax>
Date: Tuesday, July 2, 1996
Tom Brown <tomb [at] hawaii__edu> writes

>Recently some library staff members have been concerned about any
>possible dangers when using a vacuum cleaner in close proximity to
>audio and video tapes.  Does anyone know of any dangers to the
>magnetic material or if there are any guide lines for this, and if
>so, what they might be?

Generally speaking most modern magnetic media has a high
"coercivity" factor which means that a strong magnetic field is
necessary to change the direction of the magnetic field and
potentially damage the recording.  In practical terms, this means
that a very strong magnetic field must be in close proximity to the
media for a short period of time to do any damage, or a weaker field
must be in very close proximity for a long period of time.  Early
magnetic media (audio tapes for example) had a much lower coercivity
than most modern media and therefore are more sensitive to strong
magnetic fields.  Most vacuum cleaners operate for very short
periods of time and normally are not in close direct proximity to
media, and as such the risk is probably minimal (or nonexistent).  I
would not, however, place a large motor that operated for long
periods of time on a shelf in direct proximity to media, nor would I
have an audio speaker (they contain magnets) directly next to media
for an extended (years) period of time.

Jim Lindner
The Magnetic Media Restoration Company

                  Conservation DistList Instance 10:6
                  Distributed: Saturday, July 6, 1996
                        Message Id: cdl-10-6-001
Received on Tuesday, 2 July, 1996

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