Baking Your Tapes is a Recipe for Success: Part 1
Bake the Flakes back into the Tape
by Rich Rarey
PUBLIC DOMAIN column for October 1995 Radio World Magazine.
|Recently, a record producer called in a fit of mild panic. He said he had a dozen two-inch reels of multitrack tape, priceless in content, and unplayable in their present form.
I inquired as to the noise the reels made as he attempted to play them.
|Remember: Don't Panic!||William Lund, Senior Technical Service Engineer at 3M's Maplewood,MN headquarters said the first and foremost thing is "DON'T PANIC". In fact, it's so foremost that he repeated: "DO...NOT...PANIC! "
According to Lund, the only 3M brand of tape stock affected is 226,227, and to a lesser extent 806 and 807, manufactured from 1978 through the early 1980's.
Tom Neuman Senior Staff Engineer in charge of the Recording Technology Group at Ampex Corporation's Redwood City's headquarters had a similar response to those asking about tape shedding: "DON'T PANIC!" Neuman says that various Ampex tape stock from the early 1970's to early/mid 1980's has been found with the syndrome from two inch Quad video tape,to half-inch EIAJ video tape (the industrial/educational Sony "Rover" format) and the ubiquitous Ampex 406 1/4inch analog mastering tape. Because the 406 stock was a big seller, with about one million reels leaving the Ampex factory every year, this is the stock that affected the most users.
|How did these tapes become damaged?||To understand how these tapes wound up with Sticky Shedding Syndrome, it's important to view the manufacturing process from a historical perspective. Originally, the magnetic oxide was deposited on a paper backing. Paper had serious drawbacks. Moisture could cause the backing to grow and shrink. As the noise level of recording tape is dependent on the smoothness of its oxide surface, paper's microscopically rough surface made it impossible to make a smooth oxide layer over a such a rough backing.
Acetate, according to Bill Lund, made a smoother backing material, but it was water based. DuPont's Mylar (polyester) made an excellent backing material, tough, smooth and stable.
Attaching an oxide coating to polyester is harder than just painting it on; the raw oxide has to be ground to a fine evenness, without clumps or odd size particles, as the nature of high quality magnetic recording dictates that the particles must be regular and small. The oxide is mixed in vats with a binding agent that Lund describes as an "exotic, organic soup".
|Why aren't all tapes affected?||How is it, then, that certain tape stocks became sticky and shedding? According to Tom Neuman, no two chemists agree as to why> it's happening, but the effect is this: the binder's long,complex polymer chain breaks down into smaller polymer chains that might be likened to a set of microscopic sticky tinker toys.
It these unbonded parts of the chain that appear to cause the stickiness. It's believed that the particular combination of a certain oxide with a particular binder will, over time, cause the binder to break down.
Moisture in one's archive storage area will exacerbate the breakdown. Neuman says the analytical tools of the 1970's weren't sharp enough to reveal the binder limitations at the onset. Tape deterioration was recognized in the early 1980's when a major remastering phase for the emerging Compact Disc technology occurred. Users found their irreplaceable tapes sticky and unplayable.
|The answer's in the "mix"||Ampex chemists then started analyzing the problem as the frustrated users tried their own home-brew solutions, from talcum power (don't even consider this--it'll rip the oxide off the backing and ruin your heads) to alcohol washes (this will merely swab the oxide off the backing, and ruin your tape).
The chemists discovered the only cure was...to recure the tape through careful heating. During heating, the binder's stubby chains rebonded into the proper longer chain, and made the tape almost as good as new.
to use the recipe
|Here's the recipe for restoring your tapes, as patented by Ampex (don't worry,anyone can use it!). First, get a reliable, even heat source that can maintain 50 degrees Centigrade (about 121 degrees F.) plus or minus a few degrees. Many people use a convection oven to restore their tapes. It's just an oven with an internal fan to ensure even heating.
Bill Lund reports that some are using a food dehydrator oven that makes an inexpensive heat source. Tom Neuman says that one record company constructed their oven from a cardboard box, a hair dryer and a candy thermometer!
Ampex uses a BLUE M industrial laboratory oven for their research, this unit costing in the hundreds of dollars.
The key is: RELIABLE HEAT TEMPERATURE. A candy thermometer in the oven will help you monitor the desired temperature. Neuman says that regular cooking ovens should be avoided; their thermostats may not have high enough "resolution" to deliver consistent heat at these "low" temperatures.
|The Problem is
|Tom Neuman says that he has seen tape from every manufacturer exhibiting Sticky Shedding Syndrome. Why? Every tape manufacturer has to turn to a
small handful of companies for the raw materials that compose recording tape; petroleum companies for plastic materials and pigment companies (!) for the oxide. It's
not the ingredients that make a recording tape unique, Neuman says, but rather the unique way the raw materials are processed into the complex material called recording
In Part 2 We'll cover additional restoration information and give you a recipe for eliminating mold from your tapes.