Mickey:
The original AMPEX process called for 50C for "baking" tapes with hydrolysis. Later testing shows that slightly higher temperatures work better for some tapes. Other tests show that lower temperatures don't work as effectively. DA88 is PEN based as opposed to PET, as was used in earlier tapes, such as 1/4" audio. Research (a long time ago) indicated that PEN is more subject to heat than PET. It was long enough ago that we did the research that I don't remember the temperature parameters. I simply use 50C on DA88s since I have done so before without problems.
As for using lower temperatures, you can actually treat tape binder hydrolysis at room temperature (or even lower), if you have the time and proper equipment. Treatment of hydrolysis at room temperature takes months, instead of days, and requires the tapes be isolated in a vacuum chamber or a chamber with extremely low humidity (preferably below 10% RH but under 20%RH works). Most people don't want to wait months to treat hydrolyzed tapes nor do they have vacuum or low humidity isolation chambers.
FYI: low temperature (refrigerated at very low humidity) treatment of tape can be useful as a process (of last resort) to treat binder-base adhesion failure. There are, however, some potential issues. First, it often increases the presence of "white powder" residue on the tape surface. This can be cleaned off before playback. It can, however, with severely hydrolyzed tape, also cause forced cross-linking of oligomer residue into polymers on the tape surface that result in areas of increased head-to-tape separation. Unfortunately, this effect cannot be fixed or cleaned off either physically or chemically.
Peter Brothers
SPECS BROS., LLC
973-777-5055
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Audio and video restoration and re-mastering since 1983
-----Original Message-----
From: Association for Recorded Sound Discussion List [mailto:[log in to unmask]] On Behalf Of Mickey Clark
Sent: Wednesday, May 26, 2021 1:53 PM
To: [log in to unmask]
Subject: Re: [ARSCLIST] DA88 eight-track tapes with binder issues.
Stewart - I see the recommendation was a maximum of 50 degrees. Would a setting of 45 degrees be a safer margin? - Mickey
-----Original Message-----
From: ARSC
Sent: Wednesday, May 26, 2021 10:14 AM
To: [log in to unmask]
Subject: Re: [ARSCLIST] DA88 eight-track tapes with binder issues.
Hello,
I appears to be sticking throughout. I have a incubator so i can get the adjust the temperature to 50C. How long would you bake them fore?
Thank you.
Stewart Adam
Creative Audio Works LLC
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www.creativeaudioworks.com
On May 26, 2021 at 1:01:28 PM, lists ([log in to unmask]) wrote:
Is the tape sticking throughout or just in spots? If it is sticking throughout, it could be hydrolyzed and we have had some success with incubating (baking) DA88 tapes. If you do try to bake these tapes, however, you should use great care and make sure your baking unit is stable and does not go above 50C. DA88 has a base of PEN, rather than PET, and, I seem to remember that, PEN is more heat-sensitive than PET.
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