Am late to this discussions but thought I might add a few comments.

Yes, you can incubate (bake) audio cassettes and it works quite well, in some circumstances.

If you try the desiccant only method, it does take a few months. Also, you should seal the tape(s) with the desiccants inside an airtight container such as a double closure freezer bag.  Just putting them in a box (depending on the box material) can allow too much exposure to exterior humidity conditions.  Moisture can move fairly freely through cardboard box walls.  If you seal the tapes in an airtight container, there shouldn't be any reason to replace/reactivate the silica gel.  Even when the gel color coding goes clear, if the container is airtight, you have created a low humidity micro-environment in the sealed container.  Silica gel will only reduce the RH in the sealed container to a certain degree and repeated replacement of the silica gel will have minimum extra effect.  The chemical reaction that reduces the effects of SSS in a "low humidity only" treatment protocol is long-term and is based on the extended exposure of the tape material to the low humidity.  The reaction will continue in the low humidity micro-environment even when it appears that the silica gel is expended.

We also have built an audio cassette cleaning machine with which we have very good success.  Of course, we do disaster recovery on magnetic tapes so developing additional cleaning protocols/equipment  was necessary.  We have found, however, that having the machinery- cleaning other audio cassettes that have not been in a disaster has been beneficial.

Peter Brothers
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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 Eero Aro
Sent: Sunday, April 8, 2018 4:17 AM
To: [log in to unmask]
Subject: Re: [ARSCLIST] Sticky tape BASF LH Super Red Cassettes


Thanks for the comments.

For the moment, I have thought about these things:

It could be useful to change the silica gel bags in the box after maybe a couple of days. Then put the removed bags in a warm place so that they would release some humidity from them. Then swap the bags again.
And try a longer desiccation time, as Corey suggests.

I also thought that I could remove only one half of the cassette shell and pile the silica bags on top of the visible reels. Sometimes the tape reels are quite loose, although it isn't too difficult to move them as they are so small.
To make handling easier you can spool the tape somewhere in the middle.

I have had about 15-20 small silica bags in the box with the tape. The bags are about 3 x 4 cm in size. I also have some a little bit larger bags.

I have kept the box closed, it isn't necessary that humidity from the room gets into the box.