Humidity and Magnetic Media Was: Re: floppy media failure

Al Kossow aek at bitsavers.org
Tue Apr 10 18:27:50 CDT 2007


 > I am in the process of reading a couple of papers[1] on the effects of
 > humidity on magnetic recording tape

There is a patent Ampex got on tape baking. Don't have my copy handy.

Dig around in the classiccmp archives, this has been discussed about
a year ago. The failure mode is reversable by removing the H2O in the
binder with heat/humidity reduction. For tape, I have been using a
heated dehydration chamber (modified 'dry box') 50degr C, <10% humidity
for about 24 hours.

The trick with tape is to have a LOT of air moving to get into the reels.

On 1/2" tape this is normally enough to prevent enough binder shed from
clogging the heads for a single pass over the tape w/o retries. You DO NOT
want the tape to stop! If it does, the built up binder will deposit itself
on the surface of the tape in a vertical stripe. If you are lucky and that
happens, it will occur in an inter-block gap, if not, you've just created
a permanent failure (you can't clean it from the surface of the tape).

There are some other tricks, like using magnetorestrictive transducers and
low tape pressures, but that requires extensive modifications to the tape
transport.






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