Baking Your Tapes is a Recipe for Success: Part 2
Part Two:Follow up, and, what about the mold?
by Rich Rarey
PUBLIC DOMAIN column for October 1995 Radio World Magazine
|We've received engaging E-Mail from several readers for our "Bake the Flakes Back into the Tape" column of several months ago. Greg Guarno asked us the following:
1. What are the audible effects of 'baking' the tapes? I have heard that it dramatically increases 'print through', and that it may erase some of the high frequencies.
|I posed these questions to our two tape experts: William Lund, senior technical service engineer at 3M, and to Tom Neuman, senior staff engineer in charge of the Recording Technology Group at Ampex. Both experts said baking tapes at the prescribed temperatures will have no apparent audible effects.
Neuman says a temperature at 120 degrees F does not affect lubricants or other additives, it does not destroy splices, plastic reels or leader materials. He adds that after personally baking 2,000 tapes, he has not noticed any adverse effects. Lund says that high frequencies do reside nearest the actual surface of the tape, but unless that surface is disturbed in some way, the baking process does not change the magnetic properties of the oxide particles which make up the magnetic coating of the tape.
In Tom Neuman 's opinion, the only risk during baking would come from stray magnetic fields inside the oven from the electric fan motors, heating elements or solenoid coils. He adds that it's a good idea to check for any such stray fields before baking a tape in an unknown oven.
|What is print-thru? A definition||Print-though, according to our old Audio Cyclopedia, is the "unwanted transfer of a signal from one layer of tape to another by magnetic induction". According to Bill Lund the print-through phenomena is also not well understood and even more elusive to quantify.
He says it is a characteristic of the oxide used and how it is prepared for use in the chemical binder of the tape. Interestingly, print-through reaches a "terminal value" after a period of time. That is, the tape will achieve the most print- through it can have, and the amount of print-through thereafter will not increase.
The time it takes for a tape to reach this "terminal value" is dependent on the tape (and the oxide used on it) and the storage temperature. Lund says that since the oxide and the tape are pretty much fixed, the biggest variable is temperature. A tape stored at a very low temperature will take a considerable time to reach it's terminal value for print-through, whereas a tape stored at high temperatures will achieve it's terminal value much more quickly.
The terminal value is the same in both cases, it just takes much longer to get there at low temperatures.
He advises not to worry about the 'baking' process and it's potential for causing harm to the valuable tapes, because it doesn't happen.
|What are Ampex and 3M doing differently? Tom Neuman says that when the sticky shedding syndrome was first noted and the effect fully understood about nine years ago, ALL tape manufacturers began the process to improve the tape's archival stability.
Bill Lund points out that "you do not build a new binder and chemistry overnight", but rather attempt to design new tape stocks with greater longevity. He points to 3M's 900 series of tapes as such an attempt, but cautions that even with all manufacturers using accelerated aging tests to predict the behavior of their product, the outcome is still...a prediction.
The binder problem did not appear until 7 or 8 years after introduction of the product, and since predictions didn't show the problem at all, Lund says it "hit us as a real surprise". One interesting aspect of a particular product's age, Tom Neuman points out, is that manufacturers don't have control over the age of tapes sold by some of the supply houses around the country.
A reel purchased 5 years ago could actually be 8 or 10 years old. Neuman recommends buying tape stock from well known and reputable distributors, and avoiding garage and surplus sales, where, he says,"nobody has any idea of how the tape had been stored or the actual age of the tape."
|Bring back the old
tape formulation -NOT!
|Why then, with all the excitement over binders becoming unbound, don't the tape companies return to the old tried-and-true formulations that worked so well?
3M's Bill Lund says that in the quest for tapes with higher output, lower noise and lower print- though, different oxide technologies were required. The modern, better-performing oxide formulas are chemically incompatible with the older binders from 40 years ago.
Consequently, if manufacturers were to return to those old binder compositions, we'd see a return of tape stocks that had inferior print-through, maximum output, and bias noise floors.
|Author's note: Since these articles were published in 1995, the tape industry has changed dramatically; 3M no longer manufactures recording media, and the division of Ampex that made recording tape has been spun off, and is now known as Quantegy.
Bill Lund is working with 3M in their commercial graphics division. You can reach him at email@example.com,
or at firstname.lastname@example.org.
Tom Neuman has left Ampex and is persuing interactive media development. You can reach him at
Interestingly, Bill Lund says Quantegy has recently purchased 3M's recording media intellectual property rights and remaining tape stock.