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"Baking" old open-reel tapes

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Hi. I've posted about the fact that I'm going through all the dozens of cartons of old tapes that I have in storage, and transferring them to digital so that I can (as the case may be) donate the originals or, for the most part, discard them. Many of the tapes are open-reel recordings that I made in the 1970s and early 80s on Ampex 406 and 407 tape. Those types of tape are at the epicenter of the "sticky shed syndrome"--the tapes are permanently ruined if you try to play them, unless they're gently baked in a convection oven at a controlled, low temperature first. See attached photo for some tragic results from this afternoon--remnants of the oxide layer of part of a tape; it separated from the backing when I pressed "stop" while winding the tape.

Since I have so many of these tapes, I decided to get my own oven, rather than to bring tapes by the dozens to a transfer engineer who does this baking as a side service. I'll only need it for maybe six months, but it takes me over an hour each way to get to and from his shop, so it makes relative sense for me. I plan to practice on a tape that's already badly damaged; then once I get the hang of it, I'll bake all Ampex tapes pre-emptively before trying to transfer them. My current understanding is that the temperature should be around 130 degrees Fahrenheit and the baking time should be maybe 4 to 6 or 8 hours. I sure hope this works ...

--best regards

DSatz, you missed my overview of tape baking at the August AES Tea Time Topics! PM me for the outline notes.

There is a wealth of info on the web, but some of it is old, some wrong, etc. and there is a lot to sift through. I suggest starting with the Ampex patent for tape baking, which suggests 52-54C (122-129F). Then the short answer to time of baking is that it depends. Many people recommend longer times now, it seems, such as 24 hours, where you used to hear 6-12 hours. This may be that the decomposition is now worse, or some people have 2 inch tape vs. 1/4 inch, or something else. Extra time does not seem to be harmful.

If I remembered any of the tricks of the engineers I worked with years ago I'd spew them out, but I'm familiar with oxide flying off a 2" tape like Pigpen just walked through the room. If the Ampex technique isn't working for some reason I'll ping a couple of those guys for you. Good luck.

Yes, I've experienced one example of the oxide separating from the backing out of thousands of baked reels, so it does happen. I haven't seen any tips on preventing or predicting this.

I've also heard using a food dehydrator can in some cases provide good results as the temperature can in some cases be more consistent and precisely controlled. 


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