WORLD CONFERENCE ON RECORDS AND GENEALOGICAL SEMINAR STORAGE DEVICES--THEIR POTENTIAL AND RELIABILITY
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Publication Date:
August 5, 1969
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WORLD .CONFERENCE
ON RECORDS
AND GENEALOGICAL SEMINAR
Salt Lake City, Utah, U.S.A.
5-8 August 1969
STORAGE DEVICES - THEIR POTENTIAL AND RELIABILITY
By
Frederick W. Babbel
"Record Protection in
an Uncertain World"
ARL
coPrRicKT~?
4mm "MeWse?0~~~l~oFt SAINT~, INC.
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STORAGE DEVICES -THEIR POTENTIAL AND RELIABILITY
By
Frederick W. Babbel
"Forever and a day," is an expression that many a bride
has heard when she asks her groom if he will love and cherish
her always. No doubt the groom felt he was telling the truth, but
the facts of history prove that all too many couples get married
for better or worse, but not for good.
"What", you may ask, "does such an expression have to do
with the potential and reliability of magnetic devices ?" At this
stage in our history it has real relevance. Magnetic storage de -
vices of the kind we are to consider here are about the same age
as a young bride. Those who wish to promote their wares tend to
make rather optimistic claims. Those who are trying to forecast
the future in terms of what the past can tell them tend to make
ultra -conservative predictions.
Our job today is to try and find a reasonable middle ground
that is both realistic and full of promise. Producing such a com-
bination requires nearly the blind faith of a twitterpated groom.
It is within this framework, however, that we will conduct our
examination for discovery.
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Since the past can give us some valuable insights into what
the future may hold, let us first familiarize ourselves with a brief
historical review of the development of magnetic recording devices.
I am sure you will find this both informative and interesting.
The concept of recording information magnetically first be -
came operational in the 19th century. Valdemsr Poulsen, sometimes
referred to as Denmark's Edison, built a device in 1893 known as a
"Telegraphone." Steel piano wire was used as the recording medium.
In spite of some shortcomings, it worked surprisingly well. Until
the development of the vacuum tube, however, some 25 years later,
there was no adequate means available for multiplying the signal
strength to a desirable level.
This fact did not discourage excited American investors.
They raised over $5 million to market a commercial version for
use as a dictating machine.- The typewriter had just been born a
few years earlier and this looked like a good companion tool. The
typewriter managed to survive while the Telegraphone died out for
lack of sufficient interested purchasers. Nevertheless, an impor-
tant milestone had been crossed.
From that time the concept of recording information magne -
tically never died. Independent laboratory experiments continued
during the next 35 years, chiefly in Germany. Steel wires and
steel bands continued to be the recording media.
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Karl Pfleumer, an enterprising German inventor, conducted
serious experiments in the late 20's and early 30's in search of
another kind of recording medium. The AEG Company (Allgemeine
Elektrizitaets Gesellschaft) combined with the I. G. Farben Industry
to take over this inventor's experiments and developed the first
practical magnetically coated tape. This tape used an iron oxide
coating. Its consistency was about like rough sandpaper. A fine
powder -like spray would fill the room when the tape was run
through the machine, but, thanks to the vacuum tube, it was an im-
mediate success.
The first commercial recorder was marketed in 1935, using
a magnetically coated paper tape. Within a short time German
radio broadcasters were using this device. Since this tape was so
much less expensive than wire and provided better fidelity, buyers
began to flood the market even though the mechanism was still
somewhat temperamental.
Interest spread to the United States. Two recorders, using
steel tapes, were manufactured in this country beginning about 1937.
The "Mirrorphone" of Bell Laboratories was considered a quality
instrument, Soon it received competition from the "Sound Mirror"
produced by Brush Development. Distribution was still somewhat
limited, but the idea was taking hold.
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During World War II the United States continued development
of recorders using steel wire and steel tape. The Germans con-
tinued their development of magnetically coated tape for audio re-
production that displayed definite advantages. The needs of both
military machines for fast, accurate recording devices insured the
ultimate success and acceptance of such magnetic instruments.
Lewis A. Whitaker of Computron, Inc., relates an interesting
sidelight, as follows:
"Toward the end of the war, the advancing American army
captured intact an improved model of the German Magnetophone.
This captured recorder; was duly sent back to the U. S. and imme-
diately a minor revolution was started in the American recording
industry. The death knell had just sounded for wire and steel tape
as a recording medium.
"There is an interesting anecdote tied in to the discovery
of the German Magnetophone. Ike used this recorder, along with
the captured tape, to make a major speech to the defeated German
peoples. Right in the middle of the speech, out bellowed the voice
of the Fuehrer imploring all Germans to fight to the end--you guessed
it--the tape hadn't erased properly. Needless to say,. Ike was mad,
and a squad of technicians was red faced for not previewing the
speech."
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A flood of technicians scrambled to develop the magnetic
tape market as soon as the war ended. Magnetic tape and tape
machines, very much like our present ones, were available in rich
supply within a few years. They are becoming as commonplace
in our homes as other appliances. The Three M's (Minnesota
Mining and Manufacturing Company), Orradio (Ampex), Reeves
Soundcraft, and Audio Devices were among the pioneers in the
American industry. Today we have dozens of quality manufacturers
all over the world.
From this brief account you can realize that magnetic re-
cording tape is still, relatively, a "new bride" so far as age is
concerned. Improvements are being made almost daily in the
materials being used and in their capability and durability. We
have moved from the earlier paper ribbon coated with a crude red
oxide material similar to red barn paint to today's thin ribbon of
plastic, usually cellulose acetate or polyester (or Dupont's Mylar).
The coatings or emulsions now are highly refined magnetic oxides.
Binders are far stronger and longer lasting.
When we speak today of magnetic devices, magnetic tape is
by far the most widely used and the medium about which we have
the most experience as to its utility and archival qualities. Some
of the newer magnetic devices, which are now on the market, lack
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a sufficient history to permit valid evaluation. Some of these are
the fairly new magnetic discs and magnetic drums, the data files
(strips of magnetic tapes), and a newcomer by Magnavox Corpora-
tion, known as the Magnacard system. However, since all of them
employ a similar principle and use related basic materials, we
will confine our examination to the widely-used magnetic tapes.
Let us first take a look at magnetic tapes from the stand-
point of their potential.
An interesting summary of tape's basic features, which
make it such a desirable instrument, has been provided for us
by Mr. N. Borwick in an article published by Electronic Compon-
ents of November, 1963. Even this summary fails to list other
more recent applications which continue to increase its usefulness,
but for our present inquiry this list should suffice.
"The reasons for the adoption of magnetic tape in so many
varied radio and electronic fields may be deduced from an exami-
nation of tape's basic features, most of which are well known:
1. Tape recordings are available for immediate playback
without processing, so permitting rapid analysis and
re-recording as necessary.
2. Tape recordings may be played back many times
without deterioration, so permitting the extraction of
every bit of useful information.
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3. Tape recordings may be erased, so permitting the
tape itself to be re -used as often as necessary.
4. Tape recordings may be edited, by splicing or copying,
so permitting data or programme items to be built up
or regrouped as necessary.
5. Tape recordings may be multiple -channel, with or
without the use of multiplexing techniques, so permit-
ting accurate time and phase relationships to be pre-
served.
6. Tape recordings give very high-density storage, so
permitting several million data points to be contained
on a single reel.
7. Tape recordings have a very wide frequency range,
from d.c. up to megacycles per second.
8. Tape recordings have a very wide dynamic range, in
9. Tape recordings have low inherent distortion charac-
teristics, the onset of overload distortion being
gradual rather than abrupt.
10. Tape recordings preserve and reproduce information
in its electrical form, so permitting the recreation
of events and automatic reduction of data at any time.
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11. Tape recordings have the ability to alter the time base,
so permitting fast or slow reading of data while preser-
ving the ratios of all frequencies involved.
12. Tape recordings, when made on tape manufactured
under close tolerance conditions, give consistent per-
formance, in regard to sensitivity and frequency response,
so permitting direct comparison of recorded data from
reel to reel and from year to year."
The author then concludes his summary by saying, "This
impressive list of attributes of magnetic tape is possessed by no
other recording or storage medium. To be fair, however, each
medium in current use has one or more features which may
recommend it for special duties."
Each of you, I am sure, from your own knowledge and ex-
perience could add to this list. Include the factors of economy,
availability, and versatility, and we may well conclude that mag-
netic tapes and related devices can be considered to be excellent
storage devices from the standpoint of their utility and potential.
Whether we select such devices or not, must be determined
by how well they will accomplish the particular job we have in
mind to be done.
Most of us in this World Conference are more particularly
concerned with the second aspect of our examination, that of the
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reliability and archival or keeping qualities of magnetic devices.
Because of our concern for "records protection in an uncertain
world," this deserves serious evaluation.
Today there are many formal and informal study groups in
Government and in industry coming to grips with the archival pro-
perties of tape and similar magnetic devices. Some findings war-
rant tentative projections and conclusions. Other areas are still
too much in the examination stage to justify unqualified statements
of fact. Let us examine what we can consider reasonably certain
at this time, with the assurance that a rapidly increasing volume
of information is becoming available to us almost on a monthly
basis. In other words, this is a subject about which we need to
keep ourselves informed on a day-to-day basis.
A report published by the Ampex Corporation suggested that
the archival properties of tape should be considered from three
angles: the magnetic remanence or stability, the physical and
chemical stability of the polyester support, and the physical and
chemical stability of the magnetic coating. Stated in a little less
technical fashion, it is important to assure ourselves of the mag-
netic stability of the magnetic record and the physical stability of
the tape so that after many years we may play the tape on standard
reproducing equipment and recover the original record intact.
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Based on these three guidelines, the following conclusions
were reached:
Concerning magnetic stability, scientific studies confirm the
fact that based on the size of the iron oxide particles now in use,
we may expect magnetic permanence for at least 100 years.
Actual tests have been unable to detect any loss in magnetic pro-
perties until the tape temperature is raised to 6200 centigrade.
At that temperature the magnetic signal is destroyed, but so would
be all the tape components. In other words, there are no current
tests which have been able to detect any loss of signal with age.
Errors, however, do creep in with age. Dust particles,
improper tape handling, exposure to magnetic fields, and similar
conditions surrounding the care and handling of tape do pose many
problems and represent a potential source of errors and other in-
formation problems.
As Mr. Artel Ricks pointed out earlier in his remarks, a
recent sampling of 535 tapes by the Air Force Logistics Command
found an average of 85. 7 errors per reel. This error or drop-out
rate suggests that such a record lacks the accuracy and dependa-
bility required for an archival record.
The second factor, that of the stability of the tape base, pre-
sents some interesting observations.
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All precision tapes are presently coated on a polyester base.
This base is a single chemical entity, is chemically stable at ambient
temperatures, and does not contain solvents, plasticizers, or other
fugitive additives. Earlier tapes were not so stable. No meaningful
tests seem to have been devised to confirm such stability, but the
fact that such tapes have been manufactured for over 20 years with
no visible evidence of deterioration over this period of time would
suggest that the archival keeping qualities may be considered as a
reasonable risk. Future developments and tests will be necessary
to establish exact limitations.
In this connection one factor will be of special interest and
significance to many of you. For years the factor of humidity has
been considered to be a somewhat critical one. A recent report
by BASF Computron, Inc., dated May 9, 1969, gives some interest-
ing information concerning humidity. Other independent researches
tend to confirm their findings. They state:
"The physical and electro-acoustical properties of magnetic
tapes and films are not influenced by humidity, which means that no
particular consideration has to be given to the storage of recorded
tapes under high humidity conditions. This statement is valid for
PVC and Polyester, the base materials which we are using . . . how-
ever, not for acetate which is humidity and temperature sensitive,
needs air-conditioned rooms, and causes difficulties by shrinking
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and becoming brittle after a long storage time. "
The other factor which affects the stability of the tape base
is the matter of temperature. The base presently used has a
transition temperature of 75? Centigrade (167? Fahrenheit).
Tests for 72 hours at 1000 Centigrade--considerably above the
transition temperature- -showed no change in elastic modulus,
tensile strength, or 2 per cent offset yield strength beyond the
experimental error of the test method. The elevated tempera-
ture did distort the base since it is higher than the transition tem-
perature. Continuing tests are being made at the transition tem-
perature which should produce other interesting conclusions.
For all practical purposes it would appear that the base
material is archivally stable when maintained within the reason-
able temperature range of the material itself. It has been sugges-
ted by the BASF report, to which I referred earlier, that "in order
to maintain a high signal to print-through ratio, the storage temper-
ature must lie between4150 C and +25? C (59? F/77? F)."
This same report makes the further recommendation that
"in order to obtain an acceptable signal to noise ratio, even after
an extended storage period and at higher temperatures the print-
through process can be interrupted by rewinding the recorded tapes
once a year. " As long as print-through continues to be a major
problem, tape must be considered a questionable medium for
archival purposes.
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The third factor in our examination is that of the stability
of the magnetic coating or magnetic mix. Here less conclusive
evidence is available.
First of all, the magnetic mix is a rather complex mixture
of magnetic pigments, conductive pigments, lubricants, fungicides,
preservatives, dispersants, and a polymer binder. It is formulated
to have a specific complex of desirable physical and magnetic proper-
ties so that the tape can achieve its design specifications.
There have been no tests developed to predict the archival
properties of this complex coating. Also, long term age tests are
not available since most formulations presently used have been
developed within the last several years.
This would seem to indicate that of the three factors sugges-
ted to determine the archival qualities of tape, this is the one about
which least is known. Until more information is forthcoming, it
might be well to follow a suggestion made in the BASF report,
which we quoted earlier:
"The stability of the recording on our magnetic tapes and
films does not depend on storage time. To which degree a playback
level changes with time is only a matter of how often a tape has been
used and in this respect particular care should be taken that recorded
tapes are only played on well serviced recorders in order to avoid
mechanical damage. Cleanliness in using and storing recorded
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tapes is a predominant factor. Moreover, any remanence of mag-
netic heads and tape guides of the recorders has to be avoided in
order to prevent the recorded tape from deterioration. "
In preparation for this conference I reviewed literally hun-
dreds of documents and technical papers. I became overwhelmed
more by what we don't know than by what we know on this subject.
In some respects I felt much like the GI on a raft in the Pacific
during World War H. He and his companion had been adrift for
three days since their ship was sunk. Not a thing but water was
,
in sight anywhere. He turned to his companion and said, "Man
oh man! Have you ever seen so much water in all your life?"
To this his companion replied: "Huh ! You ain't seen
nothing yet. This is only the surface !"
On August 25, 1967, Sidney B. Geller of the National Bureau
of Standards sent a report to J. P. Nigro of the same organization.
He concludes the report with a summary which brings our overall
problem into rather sharp focus, as follows:
"In the past, the systematically preserved media often had
intrinsic archival value beyond its use as an alphabetic information
carrier (as for example, legal or historic documents). The present
and probably future trends are such that most archivalia will be in-
formation that is encoded into abstract symbolic forms. This infor-
mation will have intrinsic properties which must be considered
separately from those of the medium, i. e. content density, cost
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per unit content, longevity per unit content, etc.
"Methods for the systematic and very long term preserva-
tion of all information decoding keys needed for the recovery of
the original information from the abstract contents must be devel-
oped. The decoding keys must also include the physical trans-
ducers.
"Due to the large increase in new information storage
media some sort of archival quality test must be devised in order
to make effective decisions. Any choice that is made will be the
result of compromise and trade-offs because at the present time
no one medium meets all requirements. The choices will be made
on the basis of several independent needs, that is, one medium
may be chosen for its superior longevity (hard) while another may
require good updating capabilities (soft). It may be determined
that a soft content medium can be permitted greater volume and
lower density while a long-term storage medium must have ex-
tremely high information density in small volume. As an exer-
cise, why does the stone tablet which has great longevity fail as
a modern medium? It would seem that soft contents with the po-
tential longevity of hard contents would approach the optimum case.
Then he concludes with these two brief observations:
"When the medium choice is being made, the total system
which it will require for its operation must be considered as an
indicator of 'archival quality'. A complicated system will prob-
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ably be more difficult to preserve or recover on a long term
basis.
"The relationships of media to the information content
should be studied. The resurrection of lost contents and the con-
version of the contents into new forms made possible by expand-
ing technologies over the ages should also be considered on a
continuous basis. "
That summary pretty well brings into focus the long-
range problems we face in making our choices. Meanwhile, on
the basis of the evidence presently available, we cannot consider
magnetic tape at this time to be an adequately reliable archival
storage medium or a substitute for hard copy or microfilm for
permanent storage.
For the present, at least, it would seem that we must ex-
amine other alternatives available to us if we are to safeguard
the integrity of information and preserve our vital records in an
uncertain world in a practical form for the easy use of generations
yet unborn.
Thank you !
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BIBLIOGRAPHY OF PRINCIPAL SOURCES
AGEING OF MAGNETIC TAPE: A CRITICAL BIBLIOGRAPHY AND
COMPARISON OF LITERATURE SOURCES, P. S. Davison,
P. Giles and D. A. R. Matthews, Computer Journal II 241-6, 1968.
ARCHIVAL PROPERTIES OF TAPE, K. Famulener (Ampex),
25 January, 1967.
CAN THE COMPUTER HELP THE ARCHIVIST AND LIBRARIAN?,
Artel Ricks, World Conference on Records, August, 1969.
THE CHARACTERISTICS AND APPLICATIONS OF MAGNETIC
RECORDING TAPE - PART I, N. Borwick, Electronic Components,
November, 1963.
A COMPREHENSIVE LOOK AT MAGNETIC TAPE REHABILITATION,
E. P. Brandeis, Data Processing Magazine, October 1965.
COMPUTRON BULLETIN, Lewis A. Whitaker, Published by
Computron, Inc. (undated).
DERIVING MAXIMUM UTILIZATION FROM COMPUTER TAPE,
George Armes, Computers and Automation, November, 1964.
EFFECTS OF STORAGE ON DIGITAL MAGNETIC TAPE, Reports
Phase I and II, Wolf Research and Development Corp. , Prepared
for Goddard Space Flight Center, (March 28-May 15, 1968).
GUIDELINES FOR LONG-TERM RETENTION OF MAGNETIC TAPES,
S. E. Boyer, Jet Propulsion Laboratory, (Draft Copy, May 22, 1969).
HOW MUCH PROTECTION FOR MAGNETICALLY RECORDED DATA?,
Gregory M. Dillon, Systems & Procedures Journal, October, 1966.
MAGNETIC TAPE-HANDLE WITH DUE CARE, Charles E. Hearnshaw,
Automation, May, 1967.
MAGNETIC TAPE - STATE OF THE ART, Ed Schmidt, Instruments &
Control Systems, June, 1964.
MAGNETIC TAPE TRENDS, Ampex Corporation, Bulletins Nos. 1, 2,
3, 4, 6, 8, 9, 10.
MANUFACTURE AND PROPERTIES OF PROFESSIONAL MAGNETIC
RECORDING TAPES AND FILMS, J. P. Deriaud, British
Kinematography, Vol. 43, No. 4, October 1963.
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MONOGRAPHS, Memorex, Nos. 3, 4, 5.
PERMANENT STORAGE MEDIA, Paul C. Constant, Jr., Instruments
and Control Systems, Vol. 34, February, 1961.
PERSONNEL, MACHINES AND DOCUMENTATION - ESSENTIAL
INGREDIENTS FOR AR CHIVAL INTEGRITY OF COMPUTERIZED
FILES, James P. Nigro, National Bureau of Standards, (undated).
PRECISION MAGNETIC TAPE, John M. Ricci, Datamation, October 1966.
PRESERVATION AND STORAGE OF SOUND RECORDINGS, A. G.
Pickett & M. M. Lemcoe, Prepared for Library of Congress, 1959.
PROBLEMS IN DIGITAL RECORDING, L. A. Ormord, Instruments &
Control Systems, Vol. 34, August 1961.
STORAGE CONDITIONS FOR BASF MAGNETIC TAPES, BASF
Computron, Inc.
TAPE DOCUMENTATION AND MAINTENANCE, Everett O. Alldredge,
Systems, January, 1967.
TAPE LIFE, William S. Latham, IRE National Convention, 1965.
TAPE STORAGE PROBLEMS, Frank Radocy, Journal of the Audio
Engineering Society, Vol. 5, No. , January 1957.
TECHNICAL TALK, Minnesota Mining and Manufacturing Co.,
Instrumentation Bulletin Nos. 1, 2, 3, 4, 5, 6, 7, 8, 10.
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