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Old 11-20-2013, 06:58 PM
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Bob Womack Bob Womack is offline
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Default The best kind of recording project

I spent the day today restoring and archiving an old recording. This was a professional 1/4" reel-to-reel audio recording of an interview in November of 1979. The original show was properly mixed through a Neve console for excellent quality. However, little-known by most people is the fact that the vast library of audio recordings over the last forty-five years is dying, much like films have been dying. The glues used to bind the oxide, where the sound is recorded, to the polyester backing, have absorbed atmospheric humidity, become liquid again, and failed. The result is flaking off of the oxide and deposition of the glue goo on the playback head and tape guides. With a typical failed tape you can put it up on the machine and play it for a few seconds and it will shed so much oxide and glue that it can literally be brought to a standstill by the drag of the debris deposits on the heads and guides. The tapes are obviously impossible to play but without immediate action they also immediately self-destruct.

As an engineer who worked extensively with audio tape for years before we went digital, I've developed an interest in restoration and archiving of tapes. Because I'm also the last engineer in the house who understands analog tape the projects naturally come to me. What has to be done is that the tape must be baked. That's right, literally baked. The preferred method is to bake the tape at 120 degrees in a forced-air drying unit like a vegetable dryer for an hour or two per 1/4" of thickness. You can also do it in a home oven. This removes the humidity from the glue and it holds the oxide to the backing again. When the tapes contain high-value program you can pay $100 and send them to a laboratory who will both dry them and chemically treat them to fix the glue. The lab sends them back to you in a hermetically-sealed bag with "use by" date. In a dry environment you get about thirty days of temporary life out of the tape by this method then it must be repeated if the tape is to be used any further.

It works like magic! I prescribed the method to a local guy who has the oven and he did the baking for me. Then I mounted the tape on my tape deck and aligned my machine to it. With a short trial play, I got the system ready and then I transferred the hour and a half of tape into a permanent digital recording. With a tiny bit of EQ and editing I was able to freshen the recording to modern standards and master it to CD. It would seem to be a routine thing but every time I resurrect one of these it is amazing to me for a wonderful old recording to be brought to life again. This particular show contained an interview between a host and a colonel in the U.S. Air Force. It might have been routine, but this colonel was the father of a wonderful man with whom I work. His father, the colonel, has since passed away. This interview might have faded away to obscurity and died with the tape but another person who is a media archivist in a tiny cubical happened to notice my friend's name on an old show description, discovered that the subject was his father, and asked me if it was possible to rescue the tape. We secured authorization for the project and this media archivist will now be surprising my friend with a CD containing a thirty-minute, in-depth interview with his father the colonel at the height of his career, in marvelous, high fidelity sound, literally like the day it was recorded.

Now that's a nice day's work.

Bob
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Old 11-20-2013, 07:18 PM
JLed79 JLed79 is offline
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Default The best kind of recording project

Very cool stuff Bob! What a great thing to do for your friend!
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Old 11-20-2013, 07:25 PM
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Interesting, Bob...
I have a lots of old 1/4 tapes. Do you just take the reel and put in the oven at 120 degrees ? What do you rest it on ? Would this also work with cassette tapes ?
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Old 11-21-2013, 06:23 AM
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The best way to do it is to get a food dehydrating oven that works by circulating warm air. It actually extracts more humidity from the tape than a regular oven. Failing that, place the reel on something that will support it. It is usually done with metal reels to prevent melting but the tape has to have been stored on a metal reel because simply spooling it over to a reel can destroy it. In this case my archivist friend took the plastic industrial 10" reel home and did it at home. He got an oven thermometer and stabilized the oven at 120' and then placed the reel in there for ninety minutes on a cookie sheet. It was good enough for one play and a rewind. Normally I suggest two hours but I wasn't sure what that would do to the reel.

I'm not sure how it would work for cassettes. There's a sheet of lubricant in between the tape reels and the cassette body that might melt. Perhaps you could disassemble the cassette, bake the tape only, and reassemble.

Bob
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