If I Knew You Were Coming I’d
Have Baked A Tape!
A Recipe for Tape Restoration
copyright 1998 by Eddie Ciletti and updated 2011
The aging of magnetic tape concerns everyone. Even as you read
this, a DAT tape is waiting to clog the heads of your most difficult-to-clean-machine.
Unlike my usual visits to the digital domain, this is a detour into the
magnetic past! Are you ready to explore the time-space continuum?
TIME TRAVELING… PLEASE WAIT!
People who make analog recording part of their daily routine take for
granted that the tape is new and the machine is operable. When called upon
to re-master or remix a vintage analog recording, it goes without saying
that the machine must be in top form AND that your business should be insured.
That said, there is one variable for which you have no control: tape condition.
This is especially true for mid-seventies era high-output tapes such as
AMPEX 406/407 and 456, 3M 250, and AGFA 468. It does not exclude those
made well into the eighties.
Don’t attempt to play a "vintage" tape before reading this article!
In order to expect full recovery, tapes that have been shelved for an extended
period deserve special treatment just like a scuba diver must slowly return
to the surface.
All tape consists of three primary components: iron oxide, the "binder"
or glue and a plastic carrier. Acetate — which does not stretch and can
be brittle — was used until the sixties. Though its oxide color is typically
reddish-brown, black oxides were also used. Mylar/Polyester eventually
replaced Acetate. It handles stress well and never becomes brittle. Sixties-era
Mylar tapes with black oxide will be the least problematic.
Figure One shows how easy it is to identify Acetate simply by
holding it up to light.
(Acetate is translucent and Polyester is opaque.)
Tapes that have been poorly stored like the photo "uneven wind" will
require extra care.
Over time, the glue that binds the oxide to the plastic will absorb
moisture and "break down." The symptoms of "binder breakdown" are immediately
obvious even when rewinding. Tearing sounds and sluggish behavior
are clues to quit before the oxide comes off. Machines with
stationary lifters (Ampex 440/1200, MCI and 3M) will, in many cases, stall
well before reaching the halfway point. An older Studer, with its rotating
guides, may not reveal any warning signs until the tape is played.
Playing a bad tape is not recommended. Just trying to get through a
three-minute pop song will require several cleanings. Once the precious
sonic material collects on transport parts it is worthless, not to mention
difficult to remove. Do you really want to risk damage to the master for
the sake of getting a transfer? There is hope, so be patient.
Figure Two: Snackmasterâ FD-50
SHAKE ‘n BAKE: Part I
Several years ago it was discovered that baking tape at low temperature
reactivated the binder making tapes playable as new. While convection ovens
and hair dryers have been called into service, the most elegant and affordable
solution came from my brother-in-law Gary, a metallurgist in St. Paul,
The device de jour is the Snackmasterâ
Pro model FD-50 made by American Harvest
(800-288-4545). At $85, with shipping, it comes standard with
four trays, each of which can comfortably handle a reel of half-inch tape.
(Additional trays and jerky mixes can be ordered. Allow four weeks for
delivery.) To accommodate one- and two-inch tapes, modify one tray by cutting
out the plastic spokes along the perimeter with a wire cutter. This creates
a "dummy tray" adding height to the tray below.
Figure Two shows the dehydrator as intended, with standard and
modified trays overhead. Do not process food and tapes together!
The FD-50 features an adjustable thermostat and a built-in fan to circulate
the air. I checked for dangerous magnetic fields and found none, though
I do use the upper trays just to be safe (the fan is in the bottom of the
unit). The heat is adjustable from 95° F
to 145° F and is accurate within five degrees
when checked with a photographic thermometer.
STORAGE and HANDLING TIPS
Storing tapes "tail-out" after having been played minimizes the effects
of "print-through" and improves the chances of long-term survival. "Print-through"
is a form of mechanically induced tape echo. The winning combination of
high record levels and fast winding will transfer signals from one layer
of tape to another. Tail-out storage will hide print-through as "post echo."
If you discover that the tape is unplayable while in fast wind, come
to a slow stop. Fast winding the tape may cause further damage because
oxide may adhere to the back of the previous layer. In addition, old splices
may come apart. For the safest journey to the head, play
the tape backwards first, then forward to create an even
The best machines for winding traumatized tapes are those with ALL rotating
guides. The AMPEX ATR-100 and most Studer machines are well suited to the
task. In addition, you will want to remove the head assembly otherwise
a gooey oxide/binder cocktail will quickly collect on all stationary surfaces
(heads, lifters and guides). Model 800 series Studer machines are dangerously
powerful so don’t use the remote, pay close attention and be ready to stop
at a moment’s notice.
If uncertain of the tape’s condition but the pack is good, bake it anyway.
not bake Acetate!!!
When baked, the tape will expand and become loose around the hub. For
this reason, use flanges to protect the tape from coming apart. Cooking
temperature is between 130°F and
140°F. Tapes wound on plastic reels
with small hubs should be rewound onto large reels with NAB hubs. Be careful
to thread the tape around the hub without any "folds." The goal is to minimize
"mechanical distortions" that can be impressed upon subsequent layers causing
dropouts. The "wind" must be smooth as if played!!!
I have received several e-mails regarding "cooking time" and temperature.
Provided the wind is smooth, I am not afraid to bake a quarter inch tape
at 135°F — for two hours — flipping
every half-hour. You will find that cooking time varies with tape
width, type, brand, condition and the number of reels being baked.
Ampex tape from the seventies might require twice as much time as 3M tape
from the eighties (as reported by Wendy Carlos when restoring her masters
from that time period). Table One below can be used as a guide.
Baking Time varies with temperature and condition
(applies to all)
1 hour to 4 hours
Position near top cover and flip every half-hour
2 hours to 5 hours
Assuming "tail-wind," play backwards after wrapping cloth over
3 hours to 6 hours
Check for splices and shed
4 hours to 8 hours
Bake 1/2 hour for each 1/4-inch,
flip every 30 ~ 60 minutes.
Table One: Recommended baking Time and Tips based on temperatures
ranging from 130°F to 140°F.
If you are conservative about time and temperature and the
tape still sheds after baking, put it back in! Being conservative
for the sake of not losing high frequencies is a bit silly. Shedding
during a transfer can be annoying at best and a pain-in-the-ass if you
don't discover the flaw until way after the time of transfer. If
you are concerned, consider baking a tone reel or test tape for evaluation
purposes. Test tapes are not immune to shedding. Based on my
experience, tapes can be baked more than once. Afterwards, return
the tape to its box, allowing it cool for the same amount of time it was
baked as a precautionary measure. Not all machines are equally gentle,
a warm tape is more likely to stretch than one at "normal" temperature.
To confirm the process, I sandwich a piece of cloth around the tape
while rewinding. Figure Three shows what happens when the
tape is not baked. A minimal amount of oxide shed is normal. Excess shed
will cause friction to build up within the cloth. If so, re-bake.
Figure Three: An unbaked tape leaves a trail
POST RESTORATION STORAGE
I recommend wrapping the tape in a plastic bag and including a Silica
Gel pack to absorb moisture. Several surfers have dropped by to pass
along these sources for helping to improve shelf life...
A CLEAN MACHINE
Worn heads will aggravate the process of getting a good transfer. Figure
Four features multiple views of a two-track head. Lighting anomalies
conveniently darkened the wear pattern of the "worn head," which appears
as a horizontal bar in the center. From the side-view, arrows point
to where oxide gets trapped in the grooves worn by the tape. Use a toothpick
or business card to remove stubborn dirt.
Figure Four shows three views of a two-track quarter-inch
Worn heads like this one should be re-lapped to improve high-frequency
response and reduce low-frequency muddiness. To prevent a future groove
from trapping dirt and degrading performance, relief slots can be cut into
the surface (See the top image of Figure Four).
Looking for more on Tape Machine Maintenance?
Check out the Tape-101 series by clicking this
Other Links You Might Enjoy...
Baking uneven tape will damage the edges because
they get too hot and then you'll have permanent artifacts in the stereo
Baking at low temps - like 120 - 125 degrees
- over longer periods of time, will "fix" the tape enough so it can be
properly wound. Baking tail out is both for a good "play wind" as
well as for print through, same as "good" tape. Re-bake at a higher temp
to fully reactivate the adhesive.
Tape on small reels will have ANY mechanical
anomaly "ironed" into the tape, which is understandably bad - so again,
a "light" baking enough to allow the tape to be transferred, preferably
tail out - is the way to go. I use extra leader or buffer tape to
get the important material away from the hub, even for an NAB reel.
I hope this helps. Of course, you are
welcome to contribute to my "research fund," (paypal to firstname.lastname@example.org).
The Dehydrator is perfect for tapes, bananas and sun-dried tomatoes.
The addition of this culinary tool to your studio gear will surely generate
restoration business as well as improve client health by upgrading the
quality of their junk food. Enjoy!
Eddie has a library of tapes to restore from his days as Italian heavy-mental
crooner, "Fred Zeppole."
He is currently restoring tapes from 1976 to 1980.
I love feedback in the form of email.
Go back to the tape directory?
Go back to the main directory?