How to preserve audio from old tapes: baking tapes to transfer to digital?

Sticky-shed
The great 80s tape debacle - which I'm determined these days should be called ShedShed;) - affected a few tape types from the period. The first to be spotted & which spawned the investigation to find a cure was the Ampex 456, which was the studio mastering tape of the era.

Even if your tape doesn't suffer from it, you still need to take care, ensure paths are clean & that there's no 'simple' age-shedding, which can still happen, even if you don't get sticky-shed.

Sticky-shed is different from regular shedding. Old tape passing over the heads will cast off 'dust' [literally losing particulate of the magnetic surface] from its surface, causing loss of top-end as it starts to crowd the repro head. Cleaning the heads after each tape, or at worst each track, will give you a pass at rescue.

Sticky-shed, however, takes this one large leap further. Not only does the surface shed particulate, but the entire substrate will cling to the heads. It may squeak or judder & in the worst cases will be sticky enough to actually jam solid on a head - causing havoc .

If you get sticky-shed, you have to bake your tapes.

Do not do this in a domestic kitchen oven! The temperature control is nowhere near good enough.

Tape baking is a 'fun' task best done with either a commercial incubator [very expensive] or an American Harvest food dehydrator.
I kid you not.
They are the perfect shape for 10" reels & even have a post in the middle that the NAB centres fit round. You can get 4 ¼" tapes at a time in the regular model - double in the 'deluxe' - or by removing some of the internal shelves 2 ½" or even a 1" or 2".
All you need is the cheapest old one you can find on eBay, so long as it has a variable thermostat. You don't need any of the fancy gubbins they put in the lid of the modern ones.

I did my entire 80's Ampex collection with one, irreplaceable master tapes - took weeks, but I rescued every one. A friend of mine borrowed it a couple of years ago to rescue his, with similar success.

I did find this - Wikipedia - Sticky-Shed Syndrome whilst I was trying to remember the temperature range - 130 °F to 140 °F (54 to 60 °C) for 1 to 8 hours.
Practically, though, you should leave them a good while to warm, then another while to cool & settle before swapping batches. It's probably over-kill, but it's safe. I used to set up a batch in the evening, switch off in the morning, leaving it to cool & set a new batch the next evening.

BTW, this shouldn't wreck any edits/splices in itself, but depending on the quality of your splicing tape, it may have already degraded. Mine was absolutely fine, before & after, fortunately; including some heavily-edited 12" mixes.

Late edit - Reading the Wikipedia article [which I hadn't done previously] it says that baking drives off moisture - that is presumably why a dedicated dehydrator turns out to be the perfect machine for the task, aside from the fact it looks like it was made to put tapes in anyway ;) It has constant controlled heat & a fan system which pulls air through the device all the time you are 'baking', evaporating & extracting the moist air.

Note:
You only get one go at this.
Bake, rescue to digital in one pass. That's it. A second pass will start to degrade & a few weeks later the tapes will have reverted to sticky-shed.
[There's a little more leeway than that sometimes, but it's best to play safe.]

You can get plugins/apps these days that can correct for azimuth, wow & flutter, so if it's 'close enough for jazz' without doing a proper line-up, just go for it & 'fix it in the mix'. If you have line-up tones, transfer them too.