Tape baking problem (backing)

[TCmullet]

...After I bake a tape I run it through my machine in FFW while gently holding a lint-free cloth against the tape on the supply reel side. The cloth is full of oxide after the process and only then will I use the tape on the machine. Otherwise I would be cleaning all that crap off the heads. Even though baking fixes the sticky problem, there is still usually a lot of loose oxide left behind.

(Beck, I found this comment of yours in another thread. It's the closest thing that *may* relate to my problem. Would you please comment on it?)

Have done research on this board and elsewhere to embrace the Ampex Grandmaster 456 "shedding and baking" matter.

Bought bunches of 456 in '85-'86, and recorded on all within a few years. Am now seeking to play & digitize after storing for most of these years. 4 years ago, ignorantly attempted to play one and saw oxide buildup immediately. Local guy informed me of Ampex binder problem. Back into storage til now. Need to downsize and get rid of tapes, but not the content.

Here's what I've done so far: 10.5" pancakes were stored slow-wound on mostly metal but some plastic reels. Have now baked 16 hrs at about 130 degrees in a gas-powered home oven (no flipping). In two cases, I "played" a tape before baking. That is, I threaded it on my Technics RS1506 capstan-only (bypassing the headblock), and after a very short time (minute or two?) saw bad oxide buildup (brown).

After baking (and letting cool down a few hours), I can do the 15ips pass thru the 1506 in headless fashion and get *no* brown oxide buildup at all. (Yea!!) However, during both passes, the black *backing* partially shaves off and accumulates as black powdery flecks on the upper guides (particularly the right one) as well as falling to the table both as flecks and (sometimes) little corkscrew shavings that fall apart when you touch them. Somehow some of the black is getting on the big capstan and requires effort to get it all off after each 30 minute 15ips pass.

As this is backing only, I haven't been too worried; the oxide is great and does play again. I've been playing the tapes on Tascam 34 (ch 1 & 3) into computer. If I have done the 2 passes thru the 1506 (minus heads) at 15ips, then I get no shedding whatsoever on the 34 unless I ff/rew in which case I get a *little* black backing shed.

I thought things were going great. Was not really monitoring the dubs; was spot checking the resulting wav files. I started monitoring by headphones, and was horrified to find occasional dropouts. This is the kind of dropout where you lose the treble in one channel, it clears up (maybe) in a few seconds, you rewind and play the segment again and no dropout. I got to thinking. Seems like the tape may be *dirty*. Have never had dirty tape in all the years I did R-R (1972-1989 in spells). Furthermore, I have reason to believe that this one tape in particular has never been played since it was recorded in '87. And it was the only recording ever made on the tape. So how could it get dirty?

It was a mystery as to why the black buildup on capstan was happening when it's the *oxide* side (brown) that contacts the capstan. Between this and my sporadic "temporary" dropout problem, I'm suspecting that *backing* from an adjacent tape layer is contaminating the oxide side of the tape. If this is the case, then I'm in real trouble, as all the digitizing done so far (without real-time monitoring) is suspect, and all must be re-done to catch dropouts. But I really need to stop those dropouts. Bad enough if I had to monitor all in real-time, but even if I do, I don't have enough time to digitally splice all the retakes.

Is there something that can be done to stop the backing from flaking off at all? The baking has stopped the oxide; what about the backing?

Also realize I have to deal with the backing that's *already* contaminated my oxide. I've read that I can use a standard 3% hydrogen peroxide to clean both tape sides. Have visualized holding cotton swabs soaked w/peroxide against both sides of tape as it does 15ips pass through my Technics RS1506.

I realize all this is old hat for most folks. Have searched around the web, but haven't been able to find how to deal w/backing flake-off. Can anyone here advise? Thanks!

 

[acorec]

It sounds like your cake is slightly overdone. A gas oven is pretty unstable in the heat department. Either your tape is too far gone (most likely not) or you overheated the tape causing the backing to shrink slightly. The oxide does not shrink. What happens is that the oxide shears off of the backing and falls off in huge chunks. The "baking" process is best done in a de-hydrator or any thype of oven where the temp is regulated (with a calibrated thermometer).

 

[TCmullet]

It sounds like your cake is slightly overdone. A gas oven is pretty unstable in the heat department. Either your tape is too far gone (most likely not) or you overheated the tape causing the backing to shrink slightly. The oxide does not shrink. What happens is that the oxide shears off of the backing and falls off in huge chunks. The "baking" process is best done in a de-hydrator or any thype of oven where the temp is regulated (with a calibrated thermometer).

Thanks for your reply. However, before putting tape in, I tested gas oven pretty thoroughly. Used 2 thermometers, one analog, one digital.

Analog had 100 and 150 degrees as lowest two *numbered* marks, with an unnumbered mark inbetween. Digital was my Radio Shack thermohygrometer. Have seen it over 100 after leaving in car so figured it might work.

Found my oven *would* go low enough, in fact too low; had to crank it up a bit.

Hot gas intake is at bottom left & right edges. Flame is well below chamber to allow convection to evenly heat whole chamber. Tested various parts of chamber *away* from edges, all seemed the same. Tested temps at coldest (right before thermostat turns flame on) and hottest (right after flame goes out). Temp did not vary much, certainly not outside the vaste range of temps recommended by various sources (120-140).

Most of time (and at any part of oven not near edges) the analog said 130-135 (roughly) and the digital said 126. As some sources said 120 for 8 hours, and others said 140 for less time, I felt my situation was safe. And of course, I carefully arranged tapes to be as near center of oven as possible. (At least away from edges.)

Sure enough, after 10 hours (plus cooldown) the oxide seems to play fine (no shed-off).

I don't understand your comment, "What happens is that the oxide shears off of the backing and falls off in huge chunks". I never had any oxide falling off in chunks at all, except for before baking when it blotted off onto the capstan.

So are you saying that even though all temp readings (both digital and analog, and in multiple locations thruout oven) were below or well below a safe figure of 140, that somehow I've overcooked the backing? I'd read that however long you bake, you can always bake or rebake longer. Are you saying that's wrong?

Did a 2nd baking for 16 hours (a re-bake for an AGFA PE-369, a problem tape). All Ampex's still have playable oxide, but the backing still sheds. (AGFA oxide still shedding.)

 

[TCmullet]

@Beck: While I haven't heard your reaction yet, I'm suspecting you'll say I need to clean the tape both front and back.

What do you think of using hydrogen peroxide? I read about it in connection with mold. While I have no mold, perhaps cotton swabs soaked w/it should be held against both sides of tape as it passes at 15ips. Or perhaps in fast mode. What do you think?

I've had difficulty my whole life wondering about just what constitutes a "lint-free cloth". Would a fragrance-free tissue be acceptable? How about cotton-balls? How do I obtains a "lint-free cloth" or make an existing cloth "lint-free". (Sorry to be so dumb. I was mother-less at a young age and never had anyone to advise on such things.)

This subject of cleaning doesn't answer why the backing is partly flaking off. But in any case it does seem that cleaning the tape will be part of what I need to do. Will appreciate your thoughts on both matters.

 

[Herm]

The idea is to dry the tape out. A gas oven adds moisture to your tape.
You probly did more harm then good.
You need to use something like a food dehydrator that removes moisture.
As far as lint free cloth try auto motive body shop supply shops.

 

[MadAudio]

...or a convection oven.

 

[TCmullet]

Thanks, but how can that be?

1. The gas doesn't stay on more than a very tiny percentage of the time;

2. The R.H. in there was at 15 percent the whole time (darn dry if you ask *me*);

3. The Ampex tapes had a consistant *hard* failure (meaning *every* tape tried, had the "sticky shed" symptom), and this allegedly "damp" baking dried it out enough to totally stop *all* sticky shed. I mean all. Every tape so baked has had *no* brown oxide shedding, whether normal play or ff/rew. (For which I'm very grateful and happy.)

But the backing problem is still a mystery.

 

[MadAudio]

I was just looking back at your fist post - you baked them for 16 hours? Too long, in my experience.

 

[TCmullet]

...or a convection oven.

This oven is in the home of my roommate. I never bothered to examine it much before, as I don't do much oven cooking. But upon inspection, it looks to be about as "convection" as an oven can be. Along the bottom of the chamber are 2 slots along the left edge and 2 along the right. Along the back of the top are vents for exhaust.

When the flames kick on, you can open the door, look down through the left slots and see *indirectly* the flames lighting up the area down there far below the chamber. The flames never hit the chamber, which is why the chamber bottom stay cool enough to touch. They heat the air down in the flame area, then rely on convection for the heated air to rise up into the chamber.

Aren't all ovens that are not microwave, convection ovens? Even conventional electric ovens? (I don't eat from microwave ovens, btw.)

 

[MadAudio]

I think what is referred to in consumer-land as convection means it uses fans to evenly distribute the heat. But the convection ovens I've used for baking tape have both been electric.

 

[TCmullet]

I was just looking back at your fist post - you baked them for 16 hours? Too long, in my experience.

Then why do some folks (at places & forums I've visited on the web) say that it can't be too long (as long as temp isn't too hot, which it's not). And that for problem tapes such as AGFA 369, 24 to 48 hours might be necessary?

Btw, I did my first bake for 10 hours, my 2nd for 16 (mainly a repeat for my stubborn AGFA 369), and now am doing slow cooloff of a 32 hour bake for that same stubborn 369. And as extra time seems to be no harm (by most reports), I included a bunch of 7" reels of Ampex 456, to save time. Will let you know how both behaved. I thought of taking the Ampex out after 16, but thought should try this 32 on the Ampex to verify that 32 is fine for Ampex. These 7" reels are not as critical to me as the 10" reels, in case something goes wrong.

If 16 hours is "too long in my experience", does that mean you tried it for 16 hours and had bad results? What were those results? And what did you lower it to, to eliminate those bad results on a subsequent batch?

 

[TCmullet]

I think what is referred to in consumer-land as convection means it uses fans to evenly distribute the heat. But the convection ovens I've used for baking tape have both been electric.

Oh. Well that may be. Am not a serious oven user. I guess any rectangular box, whether a room with heat or a/c, or an oven is going to have cold or hot spots. But this gas oven seems to have more air flow in it's inherent design just so it can work without roasting the contents in the flames. I guess an extra muffin fan would *really* keep things even.

 

[Beck]

The residue I’ve seen after baking is a fine powder that builds up on the cloth over the length of the tape. It is more or less just a heavier than normal oxide shedding (not to be confused with sticky shedding).

I’ve successfully baked Ampex and Scotch, but never tried AGFA. There should be no difference though. I have some older 468, none of which has sticky-shed problems.

It sounds to me like your tape is still in a sticky-shed condition. The only time I’ve seen the severe peeling you describe is before baking. You can hear it ripping to pieces – awful sound.

Herm is right about gas containing moisture. I would not underestimate that as a factor at these low temps. The number of tapes you bake at a time is also important, as there must be space for air to circulate. Also the more tapes you bake at once, the more total moisture you have to eliminate.

I’ve only used an inexpensive food Dehydrator from Wal-Mart and I’ve never had a failure to fix an afflicted tape – 100% success. The food dehydrator is a completely different animal. The only time I’ve heard of a conventional oven being used successfully is with a high-watt light bulb as the heat source. I don’t recommend gas ovens because the temp extremes normally go much too high even if its in short bursts, and the afore mentioned gas/moisture equation.

Ghost has had some hands-on with baking as well. Hopefully he will be along soon with some additional thoughts.

-Tim

 

[TCmullet]

The residue I’ve seen after baking is a fine powder that builds up on the cloth over the length of the tape. It is more or less just a heavier than normal oxide shedding (not to be confused with sticky shedding).

Also, not to be confused with *my* problem which is *backing* shedding (black), not *oxide* shedding (brown). Are you talking about stuff from the Oxide side (brown) or the Backing side (black)?

I’ve successfully baked Ampex and Scotch, but never tried AGFA. There should be no difference though. I have some older 468, none of which has sticky-shed problems.

From what I could find and read, at least the PE-369 is a very severe problem. None of my voice-grade PE-36 had any problem.

It sounds to me like your tape is still in a sticky-shed condition. The only time I’ve seen the severe peeling you describe is before baking. You can hear it ripping to pieces – awful sound.

I don't think it is, because I'm not talking about brown oxide peeling off, but rather the black *backing* flaking off *sometimes*. And oxide defintely does *not* come off when I play the tape on Tascam 34 after baking and slow winding thru Technics 1506 (which DOES have the black flaking). And there's no sticking. And after the slow wind thru RS1506, the flecks gathered on the guide can be blown away. But on the capstan, they require scrubbing as they have been pressed into it by the tape and pinch roller.

Herm is right about gas containing moisture. I would not underestimate that as a factor at these low temps.

Even at only 15% r.h.???

 

[TCmullet]

Thought I'd photo the oven arrangement. (I apologize for roommate's dirty oven. Cookie sheets are totally clean, though.)

This is 3rd baking batch, done for 32 hours. (Didn't think I'd have the patience to wait that long.) It was mainly for that lonely AGFA 369 on the bottom rack. Have 6 hours of stuff on there I very much want, and the 10 hr and 16 hr bakes didn't stop the sticky-oxide shedding.

1st batch had four 10" reels on bottom shelf, six on top. 2nd batch had same.

I couldn't waste that top rack, so arranged all my 7" reels of Ampex 456. Notice:
1. The two racks are very close together, so they are both "in the middle" and not near top or bottom.
2. The 4 slots on bottom allow for pre-heated air to come in during the short times the flames are on.
3. The 7" reels are arranged to allow air flow to all reels.
4. The cookie sheets should allow any upward-flowing new hot air to disperse around sides as it mixes with slightly less hot air already over tapes. (Of course the intake slots are already at the sides, anyway.)

I could have taken Ampex out after fewer hours, but I figured these are 2nd gen. edited copies of stuff whose originals is on 10" and whose editing I will do in digital domain later, so not terribly critical to me. So I wanted to see how the Ampex would weather the 32 hours.

And I sure hope 32 hours is long enough for that blasted AGFA!

And with all those 7" reels, one can see why I don't want to do any flipping!

 

[Beck]

Lint free: An old white t-shirt works fine. (not sure if my mom even knows).

Sticky-shed involves the whole tape. The backing will separate like you describe. The goo left on the tape path is a combination of the “glue” and oxide, but the stuff peeling away in pieces includes the back coating. Sticky-shed ranges from mild to severe. Tapes that are falling apart all over the machine are in a most severe stage.

Comments on the pictures:

I wouldn’t stack the tapes, but keep one layer on each shelf. Also, the trays (cookie sheets) under the reels will prevent adequate air circulation.

A convection oven is a specific forced air type. If you use a regular oven you will have to really move the air. Air flow seems to be as critical as temp and RH.

I lack the technical (culinary) background to completely explain the reasons why people aren’t using conventional ovens successfully to recover tapes. I also think 15% RH sounds reasonable, but Ampex recommended an RH of 10% or less.

I can say these things for sure. A dehydrator will work and I bought mine on sale for $39.96 U.S. You will know it is working because after about an hour or so you will smell a light chemical odor from the tape filling the room (odor of Ampex). Also, if the baking worked the tape will be loose on the hub. The whole pancake will flop from one reel flange to the other as you flip the reel over. If the tape is still tight and centered on the hub, then recovery has not occurred. The tape should be allowed to cool at room temperature for at least as long as you bake it.

The Ampex tapes I've recovered date from 1986 - 1993. After treatment there is no shedding of oxide or backing at all.

Your baking times are really high so you should have results if the oven can do the trick.

Hope that is of some help,

-Tim

 

[BRDTS]

....."Is there something that can be done to stop the backing from flaking off at all? The baking has stopped the oxide; what about the backing?..."

Yes. The American Harvest dehydrator. 40-50 dollars everywhere. I use the fd-50 (I think that's the model). Stops the black backing from coming off from circa 1983-89 456 1" and half inch reels. That's the backing I'm talking about as well as the front. I've experienced both situations. The dehydrator works every time. Doesn't mess with the signal. I've done it a couple of times when I've had to pull out reels to transfer to daw at various sample/bit rates over the years. Never done the cloth thing as it's never been needed.

For one inch tapes, I have baked for 6 hours, turning hourly. Then let sit for another six hours. Then transfer. I believe the dehydrator recommendation on 'bake a tape" sites is half that for half inch tapes. It's been a long time since I did half inch tape, but I've never ever had a problem. Even works great on cruddy Scotch 250 from earlier years.

As to why things aren't working out on your particular setup, I don't know. But for fifty bucks, you can buy a dehydrator and try it on one of your reels. If it works (as it does for me), it won't matter any more "why" the gas oven didn't do it. If it doesn't work, take the dehydrator back to Wal-Mart or wherever. On the plus side, if it works, you can also make great dried fruit snacks to munch on while you're remixing all the old stuff in the computer.

 

[evm1024]

Anyone use a vaccuum pump while heating?

I wonder if anyon has tried putting their tapes in a partial vaccuum? I have a few sticky tapes that I can try this on. One could put them in vaccuum before, after or during heating.

--Ethan

 

[TCmullet]

I wonder if anyon has tried putting their tapes in a partial vaccuum? I have a few sticky tapes that I can try this on. One could put them in vaccuum before, after or during heating.
--Ethan

Interesting idea. I remember the concept from high school chemistry of partial pressures. The ovens or dehydrators create a lower partial pressure of the water vapor in order to pull the moisture out of the tape. Maybe a lower *atmospheric* pressure would do the same thing. One might wonder if perhaps other stuff might get pulled out that shouldn't. Maybe only Quantegy (etc) would know for sure. But how would anyone at home be able to create a partial vacuum for any meaningful length of time?

 

[Beck]

Haven’t seen any instructions about using vacuums, though I have seen it mentioned. When the problem first appeared Ampex had a program for customers to send tapes in for recovery. They used a professional convection oven. They were doing massive amounts of tape though.

The inexpensive food dehydrator accomplishes the task in the same way for small amounts of tape, and is the most common for personal use. This is what I use.

http://www.walmart.com/catalog/product.gsp?product_id=1120727

I found a few of my old links for more info. You will notice there are slight variations in methods. For example, I’ve seen it recommended to run the tape first, which I think is a really bad idea, so I don’t do it.

http://www.tangible-technology.com/tape/baking1.html

http://audio-restoration.com/baking.php

http://www.wendycarlos.com/bake a tape/baketape.html

http://www.josephson.com/bake_tape.html

http://www.unesco.org/webworld/ramp/html/r9704e/r9704e11.htm

http://beradio.com/news/radio_baking_magnetic_recording/index.html

http://www.radiocollege.org/readingroom/articles/craft/baking.php


-Tim