Corey Bailey
Audio Engineering
USEFUL INFORMATION
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’s even steeper today.
Record collecting can be relatively simple, particularly if a person sticks mostly to
vinyl LP’s. 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 most likely 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 Analog Tape
Recorders. Check out the Analog Tape page in my glossaries section for some
simple definitions and descriptions. Also visit my Links 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
azimuth, 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.
One of the most popular uses 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 clear.
Fig. 1 is a 7” reel of acetate tape
being held up to a 40 watt light. The
light transmission properties are
obvious.
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. If the Cupping condition is
not severe, there is a possible treatment that can be done called a “B-Wind”
whereby the tape is wound onto a take-up reel with the oxide out. The tape reel is
stored for a period of time to possibly reverse the condition.
Acetate tape that has become too brittle to be playable can sometimes be re-
hydrated. The short story is that acetate tape usually can be re-hydrated if left in
a moist environment. 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 and left for a period of time. The key is to not have the tape
come in contact with the source of the moisture. I have written a separate article
on this subject which goes into more detail: Moisturizing Acetate Tape If you have
old tape you suspect is brittle acetate, consult a professional or do some research
before attempting anything. The information is out there.
Polyester base tape
Polyester base audio tape first appeared on the market in the early 1950’s, and,
by the late 1960’s, it had basically 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, many 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 problems.
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 sticky-shed syndrome.
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 audio tape baking is still being debated. I discuss
the baking process in a separate article.
Identifying the track format:
One of the simplest ways 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 magnetic viewer:
Fig. 3 (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
placement.
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 on a quarter track
tape deck. 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. A quarter track tape recorded in both directions (most likely
stereo), played on a 4 channel tape deck will play both forwards and backwards
at the same time. Likewise, a quarter track tape recorded in both directions and
played on a 2 track tape deck will play both forwards and backwards at the same
time with one channel being lower in level if your machine is calibrated correctly.
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
manufactured by LAST Factory. 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 Texwipe® or any lint free cloth
with the lubricant and apply it to the oxide while rewinding or forwarding the tape
very slowly. By slowly I mean roughly 5–15 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 Last Factory’s tape preservative 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 only
anecdotal evidence to support this, but I can say that I’ve noticed no adverse
effects on my own tapes after about twenty years of storage. I have recently
added an article dedicated to lubricating audio tape.
Baking Polyester Tape:
First, I will only bake a tape as a last resort when no other restoration method is
applicable. 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.
I typically use a constant temperature of 118 - 120 degrees Fahrenheit (48 - 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 around 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.
Important:
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 several hours while monitoring
the temperature at the area where the tape is to be placed before 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
time.
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 the most 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 year
round. 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 are only a couple of manufacturers of analog tape left and
nobody, that I know of, 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.
Advice is always free and their is a ‘Contact Me’ button at the top of all pages.
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© Corey Bailey Audio Engineering
FIG 1.
Acetate Tape
FIG 2.
Polyester Tape
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.