Over time, magnetic recording tape becomes unplayable because the
binder used to adhere the magnetc material to the backing or a chemical
added to the binder becomes unstable. Tapes in this condition will
leave a gooey residue on the tape transport. This residue is comprised
mostly of the magnetic material, and playing a tape in this condition
will destroy the recording without accurately playing the recorded
There are many individual recipes for baking tapes. For the most part,
they are all similar in their process in that they are used to dry the
tape at low heat. Once a tape has been baked, it should be dubbed
within 24 hours. In most cases it is possible to re-bake a tape as
necessary to retrieve the audio, but this should not be a substitute
for copying the material, preferably to a digital format that will
preserve the audio in its highest possible quality.
Stored tape should always have a smooth wrap. Tapes stored tails out
after being played will naturally have this. Tapes that have been
rewound at high speed typically do not have a smooth wrap. If the tape
to be baked does not have a smooth wrap, try to rewrap the tape by
transferring it from one reel to another without running it through the
tape guides. This is not easy to do on most tape machines. You may have
to do your best with what you have and rewrap the tape after baking
Several methods are listed here for your reference. BE Radio makes no
claim as to the suitability of any of these methods, nor is BE Radio
responsible for any loss resulting from the use of these methods.
Place the tape in a convection oven for three to eight hours at very
135 degrees F to 150 degrees F. Remove the flanges from the reels to
prevent melting the tape.
baking, remove tapes from the oven and allow them to cool to the
control room environment for 24 hours prior to working with the tapes.
This allows the tapes to cool, relieves pack stresses, gives the
binders time to re-adhere to the base film, and allows residual
lubricants deep in the layers of the tape to exude to the surface to
make the tapes playable.
Time: 2 - 8 hours, depending on tape thickness.
Temperature: 130 degrees F, +/- 5 degrees, 10% humidity +/- 5%
After heating cycle, let stand overnight to cool and stabilize. Should
be good for a month or more.
Time: 4 hours for 1/4", 7 -12 hours for greater than 1/4"
Temperature: 130 degrees F. +/- 5 degrees.
According to 3M, there is no need to worry about electric fields
generated by an electric oven.
After completion of the heating cycle, allow the oven and tape to
return to room temperature naturally.
Rewind the tape at normal playback tension both directions. Leave the
tape tail out if it is not to be copied immediately. Otherwise, copy
the tape to another medium immediately, or at least within two days.
The copy playback should be done on a machine as perfectly aligned as
NOTE: There is no chart that specifies a certain time/temperature for a
given tape thickness or condition. Bake it for a few hours and give it
a try. If there are still problems, repeat the process. You aren't
trying to restore a tape -- just make it playable for a couple of
passes so you can transfer the audio to a more stable medium.Be sure to
use a good thermometer. Let the oven stabilize before you bake. Check
the temperature every hour or so.
Food dehydrators, such as the Snackmaster Pro model FD-50 from
American Harvest, can be used. This particular model has four trays,
which will easily hold a reel of 1/2" tape. Thicker tapes can be baked
by cutting a tray to make a sleeve.
Food dehydrators have an adjustable thermostat and a fan to circulate