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 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 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. 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 collectable! 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. 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 out there. 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 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 125-130 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 with no apparent adverse affects. 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 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. 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. 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 gage. To make sure that things are at the correct temperature, I use a very accurate digital thermometer with a probe which allows me to monitor the temperature at the tape reel itself. I typically use a constant temperature of 125 degrees Fahrenheit (51.7 degrees Celsius). You can be within 5 degrees or so and be fine. At 125 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 118 degrees Fahrenheit for 24 hours and longer with great results. Avoid temperatures exceeding 140 degrees Fahrenheit because you will risk damaging the tape. Important: Know that not all brands or types of polyester audio tape will respond to the baking process. Make absoletuly 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 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. Lubricating audio tape: This topic also deserves a separate article because baking a tape suffering from binder hydrolysis or sticky shed syndrome sometimes isn’t enough. I have found baking polyester audio tape to be about 95% effective. There are several approaches, using a number of products and chemicals currently in use, to lubricate the other 5% of tapes still in need of help. 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’ve found that I often have to use more lubricant on problem tapes than recommended by LAST Factory. Basically, I soak a cotton Texwipe with the lubricant and apply it to the oxide while rewinding or forwarding the tape very slowly. By slowly I mean roughly 5–10 Ips. You can play the tape as a convenient way to move it at a constant speed while applying the lubricant. If you do, I recommend applying the lubricant on the incoming side of the tape before it comes in contact with the heads and guides. While applying the lubricant, I use an eye dropper to keep the Texwipe wet. I will stop as often as necessary to re- fold the Texwipe if the oxide is still shedding 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 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 audio tape and acetate base magnetic film as well with good results. 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. 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 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. Return to TOP of page
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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.