ANALOG TAPE: DO IT YOURSELF?
50 years ago or so, it was easy to spot a die-hard audiophile because he or she
owned a reel-to-reel tape recorder. I was one of them. I owned an early
production-model Roberts, which was considered to be one of the serious
audiophile decks of its day. Even though the manufacturers tried to make home
recorders as simple as possible, the whole process had a rather steep learning
curve. It is even steeper today.
Record collecting can be relatively simple, particularly if a person sticks mostly to
vinyl records. One can purchase a single turntable which will play all speeds and
sizes of records. Analog tape recorders, for the most part, are format-specific,
and tapes recorded on different format recorders are not interchangeable. For
example: In order to be able to play 98 percent of the ¼” tape formats that were
used, I own (and have to maintain) four tape decks. This brings up the
maintenance issue: Tape recorders are very complicated electro-mechanical
pieces of equipment for which very few, if any, parts are still available. This also
means acquiring the proper test equipment and learning how to use it. If you want
to try this yourself at the hobby level, the most difficult task will be finding an
affordable, working reel-to-reel tape recorder to get started with. The used market
is your only option. There are some talented technicians that specialize in
restoring old professional tape decks for archival purposes. As you might imagine,
these refurbished tape decks cost professional prices. The alternatives are
consumer and “Prosumer” reel-to-reel tape decks. Some have been expertly
refurbished and good used ones can still be found.
For those who are new to analog audio tape recording, here is a link to a student
primer provided by the University of California, Santa Cruz titled
. Check out the
page in my glossaries section for some
simple definitions and descriptions. Also visit my
page. Some of the sites
there have volumes of information about playing and archiving audio tape. You
will need to learn how to identify the various formats, adjust parameters such as
and be able to get the best out of decaying tapes that have been
improperly stored for years. I’m not intentionally trying to discourage you from
becoming a collector of audio tapes; I’m simply telling it like it is and suggesting
that you do some extensive research before jumping into a hobby that can easily
turn into a money pit.
The most popular use for home reel-to-reel recorders was to make song tapes of
favorite songs from records or off-air. I made a few myself way back when. This is
the vast majority of what you are going to come across at garage sales and swap
meets. Some are OK, some are poorly made. Of course, a lot of family history
was recorded on reel-to-reel tapes, and this is what you may find in Grandma's
attic. On the other hand, there were quite a few commercial recordings made for
reel-to-reel enthusiasts, and some still survive. Some are very collectible!
Acetate base tape
The vast majority of family history recordings on reel-to-reel tapes that I have
archived were made from the middle 1950’s through the 1960’s. This was the era
of acetate tapes that are now very brittle and delicate. This type of tape is prone
to breaking and leaving jagged ends that are difficult if not impossible to repair.
Acetate tape can be identified by holding the reel up to a bright light. If you can
see light through the reel, it’s most likely acetate because the acetate base is
Fig. 1 is a 7” reel of acetate tape
being held up to a 40 watt light. The
light transmission properties are
Polyester tape, (Fig 2.) when held up
to light, is opaque.
(The light on the surface of the reel
is the camera flash.)
The one caveat here is that if the acetate
tape in question is suffering from a
deformity called cupping, it may not pass
light edgewise as well as shown in the
example. Cupping is when the edges of
the tape curl up somewhat, making the
tape resistant to wrapping on a reel. The
tape itself looks like the shape of a metal Venetian blind. Cupping results from the
tape losing moisture over time. If severe enough, cupping can cause the oxide to
fall off the backing. You will usually notice the oxide flaking condition on the outer
wraps of the reel. While making acetate tape easier to identify because the clear
base is now identifiable, flaking is non-reversible. If any of the recording has
separated from the base, it’s gone forever, turned into a small pile of oxide flakes.
Acetate tape which has become too brittle to be playable can be re-hydrated. This
discussion in detail is really the subject for a separate article, but the short story is
that acetate tape can be successfully re-hydrated if left in a moist environment
overnight. The key is to not have the tape come in contact with the source of the
moisture. This can be as simple as placing some dampened (not wet) cotton balls
in the corners of the tape box with the tape for 24 hours or so, or as complex as
making up a system which suspends the tape over distilled water in a closed
environment. If you have old tape you suspect is brittle acetate, consult a
professional or do some research before attempting anything. The information is
Polyester base tape
Polyester base audio tape first appeared on the market in the mid to late 1960’s,
and, by the early 1970’s, it had completely replaced acetate tape. Polyester base
audio tape was readily embraced by the professional audio community because
the improved oxide formulations allowed for increased dynamic range.
Unfortunately, during the mid 1970’s, a couple of manufacturers changed their
oxide formulation (namely the binder chemistry), and things started to go bad
from there. Some of those newer tape formulations had severe oxide shedding
As it turns out, that was an indication of things to come in later years.
A surprisingly large percentage of polyester tape that has been stored for the last
40 years or so, suffers from a condition known as binder hydrolysis. This is a
condition whereby the binder (used to adhere the oxide formulation to the
polyester base) has absorbed moisture over time, causing the oxide to become
soft and sticky and leave oxide deposits on all of the stationary tape recorder
parts (Guides, Heads, Tape Lifters, etc.). Quite often, the tape will chatter across
the tape heads as the result of a condition known as
Ampex Corporation, one of the manufacturers plagued by the reformulation
problems, came up with the solution of “baking” audio tapes at 130 degrees
Fahrenheit for 12 to 24 hours, depending on the size of the reel and the thickness
of the tape. Much has been written about this process, and the research
continues. Baking is a temporary solution because after a week or so at room
temperature, the problem tapes will return to their sticky state. Experience has
shown that polyester tape can be baked more than once. The possibility of
adverse affects resulting from multiple bake cycles is still being debated.
Identifying the track format
The simplest way to identify the track format of a recorded tape is to view it with a
magnetic viewer. This is a gadget that has extremely fine magnetic particles
suspended in a fluid. When placed over a recorded tape, the magnetic viewer
shows the actual magnetic recording and reveals the track format….almost. Here
are two pictures of recorded tapes
revealing their format under a
(Right) is a 2 track stereo
recording. However, it could be a
half-track mono (recorded both
directions) since the two formats
share the same track width and
If the 2 track tape is a half-track
mono, one channel will play
forward while the other channel is
playing backwards when played on
a two track machine.
Quarter track can be recorded in both directions, and if that is the case, you will
see four bands of magnetism. That would mean it could also be a four channel
recording, which shares the same quarter track widths and spacing. At least, by
viewing the tape with a magnetic viewer, you can tell which play head format to
use for continuing the investigation.
If the quarter track tape shows four bands of magnetism, you will have to play it
one direction and then turn it over and check the other direction.
If the tape plays correctly in both directions, it’s a quarter track recorded in both
directions. If one of the directions plays backwards, you’ve probably got a four
channel tape on your hands and will need a four channel tape deck to play it.
Lubricating audio tape
I will lubricate a tape suffering from binder hydrolysis or sticky shed syndrome first
because I consider baking to be a last resort. I have found that the method and
product that I use for lubricating polyester base audio tape to be about 90%
effective. If the oxide appears to be sticky or shedding during the lubricating
process, resists you in any way, stop and read my articles on baking or lubricating
audio tape to possibly determine if you should proceed. There are several
approaches, using a number of products and chemicals currently in use to
lubricate audio tapes. I use a lubricant specifically formulated for audio tape
. Check out their website. They make products for
records and tapes along with information on how to use them.
I often have to use more lubricant on problem tapes than recommended by LAST
Factory. As you may have guessed, I have a custom built setup that I use for this
process. However, you can simply wet a cotton
or any lint free cloth
with the lubricant and apply it to the oxide while rewinding or forwarding the tape
. By slowly I mean roughly 5–10 inches per second. You can play the
tape as a convenient way to move it at a constant speed while applying the
lubricant however, I would recommend threading the tape directly from reel-to-
reel. If you do play the tape, I would recommend applying the lubricant on the
incoming side of the tape before it comes in contact with the heads and guides. I
would also recommend covering the heads with Teflon
tape (it’s very slippery
and avoids unnecessary head wear). While applying the lubricant, Use an eye
dropper to keep the cloth
wet. The kit from Last Factory usually comes and
applicators so try them to see if they work better for you. Stop as often as
necessary to re-fold the cloth and wet it again. The lubricant does evaporate from
the oxide however, I have not encountered any adverse effects from the layers
winding onto the take-up reel before the lubricant has evaporated completely.
While I don’t drench the tape, I do make sure that the coverage is such that the
oxide gets wet. Because I’m coming in direct contact with the fluid, I wear rubber
gloves or disposable food handling gloves for the application process even
though I have been personally assured by the manufacturer that all of their
products are safe to handle. I’ve used TAPE LAST on all types of polyester base
audio tape and acetate base magnetic film as well with good results. I DO NOT
recommend lubricating acetate base audio tape. Magnetic film (16MM, 35MM
etc.) is different in that the acetate base is several times thicker than audio tape
and so is the oxide coating. LAST Factory claims that treating magnetic media
with their lubricant will increase shelf life. I have no evidence to support this, but I
can say that I’ve noticed no adverse effects on my own tapes after about fifteen
years of storage. I have recently added an article dedicated to lubricating audio
tape and the link is at the top of the page.
Baking Polyester Tape
I use a food dehydrator. It can be that simple. The dehydrator I use regulates the
temperature by manually adjusting the air flow through the unit. It’s a simple
dehydrator which has no temperature gauge. To make sure that things are at the
correct temperature, I use a very accurate digital thermometer with a long probe
which allows me to monitor the temperature at the tape reel itself.
I typically use a constant temperature of 120 degrees Fahrenheit (49 degrees
Celsius) or less. You can be within 5 degrees or so and be fine. At 120 degrees,
the baking time will be 8 to 12 hours. If you want to be safe, operate on the low
side and bake the tape longer. I’ve baked tapes at 115 degrees Fahrenheit for 24-
48 hours and longer with great results. Avoid temperatures exceeding 130
degrees Fahrenheit (54.5 degrees Celsius) because you will risk damaging the
tape. I have also added an article dedicated to baking audio tape and, likewise,
the link is at the top of the page.
Know that not all brands or types of polyester audio tape will respond to the
baking process. Make absolutely sure of the type of tape you have. Research it
well before trying anything.
Whatever type or brand of oven you use, it has to be temperature stable within a
couple of degrees. Because the air temperature and humidity are ever changing,
(time of day, time of year), I run my dehydrator for 24 hours while monitoring the
temperature at the area where the tape is to be placed
I begin the process
of baking any tapes.
Any oven used for the purpose of baking magnetic tape should not be used for
anything else. It should go without saying that a food dehydrator should not be
used both for food and magnetic tape.
Always, always seek advice from a professional before trying anything for the first
Storing Audio Tape
All of your audio tapes, record albums, and optical media should be stored
vertically (on edge). Store all of your magnetic audio recordings in a cool dry
place that is away from excessive heat or moisture. (So, how many times have
you read that on the label of a flour box?) Well, it’s true: keep your magnetic
media in an area where the temperature and humidity are stable. Large
fluctuations in either will accelerate deterioration. Check with your local librarian
or the internet for information on this subject. Archivists recommend an average
temperature of less than 50 degrees Fahrenheit (10 degrees Celsius) and 30 -
40% relative humidity or less. Those “ideal” conditions may be difficult to attain in
the average home, but maintaining room temperature at 30 - 40% relative
humidity (or less) is possible. This likely leaves out the basement and attic unless
one or both have been built to maintain a stable temperature and humidity.
Storing your magnetic media on the highest shelf in a centrally located closet will
probably be the most stable environment in the average home. I live in the desert
mountains on the West Coast of the US, where a closet shelf works well and the
magnetic media I have has faired well over the years.
Analog tape recording has seen a niche resurgence by artists who prefer the
sonic characteristics of analog tape. During the heyday of analog recording, there
were a dozen or more manufacturers of tape stock and as many manufacturers of
recorders. Today there is one manufacturer of analog tape left and nobody is
making new recorders.
I would be remiss if I didn’t mention again that if you have some old family
recordings and you are the least bit unsure about them, please consult a
professional before doing anything. You may have only one chance to play them.
© 2012 Corey Bailey Audio Engineering
DO IT YOURSELF?
BAKING AUDIO TAPE
LUBRICATING AUDIO TAPE
A Little About Sound
Optimizing your PC
Sample Frequency Defined
Packing Records for Shipment
Saving Your Family Video
Your Digital Data is at Risk
FIG. 3: 2 Track format
FIG. 4: 1/4 Track format
The picture to the Left (Fig 4) is that of
a quarter track stereo format to show
the difference in track width.