Tape “baking” is the process of temporarily restoring to playability magnetic tape that has aged. It is the topic of so much urban legend that finding accurate information on the subject can be daunting. It’s in your best interests to understand this process thoroughly, especially if you are concerned about the impact of the process on your media.
Tape baking applies low heat for an extended amount of time to chemically “dry out” the glue binding the oxide to the polyseter tape. It isn’t a dehydration process, though the most convenient equipment for the task are often food dehydrators.
A tape can be baked 100 times, easily. At least, that’s how many times we’ve baked an alignment reel that we leave in the dehydrator and test occasionally for degradation. There is none. The precision tones play perfectly every time.
Many clients approach us with a statement that goes “I’ve got an old reel of tape but it isn’t a roll of Ampex 456, which everybody knows is the bad one.” That broad statement follows the late 1970’s debacle after Ampex, after making changes to the glue recipe/application process, suddenly had a problem where whole swaths of oxide would separate in sheets from the master reel as the recording was on the machine. Total, catastrophic failure of the tape. It took Ampex a while to solve this, the advice to watch out for Ampex 456 was passed around as gospel and, to this day, it’s retold as legend.
But this problem is not what we are solving today when we bake a tape. We are temporarily solving a problem (among others) called “Sticky Shed.” If you imagine a reel of recording tape as a giant roll of household “Scotch Tape with rust sprinkled on it” the problem might become clearer for you. If you’ve encountered a 10 or 20 year old piece of Scotch Tape, you are probably aware that the glue because sticky and spread out into a mess. Old “cello tape” didn’t do this, it used to dry out and then fall off.
So the problem isn’t that giant sheets of your material are going to fly off as we attempt to play the reel, the problem is that the messy, sticky oxide will “snowplough” off your reel through friction with the tape heads, lifters and even rollers. This immediately and permanently affects the high frequency signals on the reel and can easily extend into the midrange frequencies. Your music is literally being scraped off of your tape. In a nutshell, this is the problem we are solving with tape baking. Through maintained heat, the chemical structure of the glue takes up and adheres the oxide back to the tape, like it was designed.
The problem is straightforward enough to identify: put the reel of tape on a machine with fully cleaned tape path and fast forward for 10 seconds or so, stop and remove tape away from the path so you can visually inspect the lifters, then note results. However, there are any number of problems with this approach.
If the reel is stored ready to play (“heads out” we call it) then we’re in danger of destroying the first note of the first song on the reel just by testing it out. The second problem is the one that convinces us that baking EVERY bakeable tape that comes in here is the right strategy for the greatest success. There is a stage of tape degradation where the tape does not shed onto the lifters as described in our test. Instead, it results in surface distortion of the tape face and causes the tape to flutter against the head during playback. You could play that reel time and again and you’d never see any (alarming) amounts of shed on the heads but it will never play right til it’s been baked (or baked some more, if we already gave it a shot).
Mr. Toad’s is convinced that the only correct strategy for best possible results is to immediately bake all “bakeable” tapes before examing them on the machine, with some caveats. Standard tape baking is included on every job, at no addional cost. It is part of the preparation process. If we discover anything that affects bakeability or adds to cost, we will let you know.
All reels of recording tape made since 1965-ish have been made with a polyeester tape baking. ONLY polyester backed tapes can be baked. Pre-1965, recording tape was made with an acetate backing. ACETATE TAPES CANNOT BE BAKED OR PERMANENT DAMAGE WILL RESULT (they use a re-hydrating technique, the exact opposite process of baking). Think of acetate based recording stock as the same as “film stock” and this will immediately make sense: we’ve all heard the tales of film archives being damaged by heat or, worse, spontaneously combusting.
This dramatic difference in the composition of the two types of magnetic recording tape used in our history is about the only aspect of this process that renders tape baking a “dangerous” process. In the hands of a professional, tape baking is safe and the preferred way to proceed with a tape transfer. There is almost no other danger that the tape will be succeptible, so once proper identification has been made, then the tape has been baked, the transfer can proceed.
There are advanced caveats to that statement. Poorly wound reels are sometimes a problem which could cause edges to distort if baked as they are presented to us. Splices, too, are an issue. If the recipe for baking the that size tape isn’t accurate, and the tape is overbaked, the splices can ooze out, requiring not just replacement of the splices at additional cost, but cleanup from where the glue spread to adjacent wraps of tape. Also, tapes in a shell, like VHS and Hi8, have to be opened and baked “on the half shell.” These do incur additional cost.
Each make of tape has its own challenges these days. For starters, assume ANY tape over 10 years old will need baking. We’ve already had to bake RMG 911 and Quantegy GP9. Ampex 456 is no better or worse than any other tape. If you had a bad reel you knew it at the time. Scotch, so proud of their “back treatment” on 226 and 250, has to be baked not only to make sure the binder (glue) takes up but to turn the now waxy lubricant into chalk that can be scraped off. AGFA 468 is a maddenly frustrating tape, either as good as it gets or two weeks in the tape baker hoping it will become playable. Only about 1 in 100 reels can’t be restored to full playability and even those aren’t total failures.
The other, horrible aspect of shedding tape is that rotten tape – specifically, reels that have been baked once yet still fail dramatically on testing – can dissolve the pot metal surrounding the elements in the recording head, destroying a very expensive tape head. Needless to say, this has helped form our “all baking, all the time” policy. Why take the risk of damaging your reel, our gear or doing a bad transfer?
In conclusion, tape baking is the preferred process for proceeding with the transfer of all polyester tape, in the hands of a trained transfer engineer. To make sure that this conclusion is teated as standard practice and not an “option” there is no additional cost for tape baking at Mr. Toad’s and is included on all open reel transfers.