ISO 18923:2000

INTERNATIONAL ISO
STANDARD 18923
First edition
2000-06-01
Imaging materials — Polyester-base
magnetic tape — Storage practices
Matériaux pour image — Bande magnétique à base de polyester —
Pratiques d'emmagasinage
Reference number
©
ISO 2000
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ii © ISO 2000 – All rights reserved

Contents Page
Foreword.v
Introduction.vi
1 Scope .1
2 Normative references .1
3 Terms and definitions .2
4 Environmental conditions.5
5 Materials .7
6 Enclosures.7
7 Preparation.8
8 Storage housing.9
9 Storage rooms.9
10 Fire-protective storage.10
11 Identification, inspection, and cleaning .10
Annex A (informative) Numbering system for related International Standards.11
Annex B (informative) Stability of cellulose triacetate base.12
Annex C (informative) Distinction between master tapes and work copies .13
Annex D (informative) Temperature/relative humidity relationship .14
Annex E (informative) Temperature and humidity acclimatization .15
Bibliography.17
Table 1 Maximum temperature and relative humidity for storage.6
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 18923 was prepared by Technical Committee ISO/TC 42, Photography.
This International Standard is one of a series of standards dealing with the physical properties and stability of
imaging materials. To facilitate identification of these International Standards, they are assigned a number within
the block from 18900 to 18999 (see annex A).
Annexes A to E of this International Standard are for information only.
iv © ISO 2000 – All rights reserved

Introduction
Magnetic tape is an important material in the capturing of information and has had widespread use in audio, video,
and computer applications over the past 60 years. Preservation of this information is becoming of increasing
concern to society, particularly as the recorded information becomes older and frequently of greater value to
libraries, archives, museums, government agencies, and commercial organizations. Magnetic tape is also widely
used by individual consumers to preserve records of personal or entertainment value.
The retrievability of the information on magnetic tape is dependent upon that of the complete magnetic system.
This includes the stability of the tape itself, the equipment on which it is run and, in some systems, upon the
necessary software. It is recognized that tape records will eventually have to be copied or transferred to another
material when the system becomes obsolete. Nevertheless, it is advantageous to prolong the tape life so that the
material does not become the controlling factor.
Although there have been many studies of tape stability, International Standards do not exist against which tape life
can be evaluated. Likewise, International Standards are not available on the life expectancy of hardware and the
problems associated with hardware wearing out or becoming obsolete. Therefore, the best approach for tape users
is to store magnetic tape under conditions that will extend its life and to handle tape so that it will not be subjected
to stress and undergo physical breakdown during use. This International Standard addresses the concerns of
storage.
A major component of magnetic tape is the plastic base. Early audio-magnetic tape was manufactured on a variety
of base materials, including paper, various vinyl esters, and cellulose esters. After extended storage, or storage
under adverse conditions, the cellulose-triacetate base decomposes and produces acetic acid (see informative
annex B). However, since the 1960s, magnetic tape has been coated onto a polyester base that has excellent long-
term stability. This International Standard was developed specifically for polyester-base tapes. However, it is also
applicable to the storage of triacetate-base tapes even though the triacetate base is not as stable.
The second component of magnetic tape is the oxide (or metal particle) binder layer which determines the
magnetic characteristics. A magnetic characteristic of importance in the aging behaviour of tape is the development
of print-through of analog tape. However, both research and use have clearly demonstrated that the critical
concerns are primarily changes in physical properties, not the loss of magnetic characteristics. Upon use and
aging, there may be changes in the friction properties, abrasivity, binder-base adhesion, and binder cohesion that
render the tape unusable. Many of these changes occur as a result of binder degradation. Unfortunately, the user
has no practical means of determining the stability of the composite tape and must rely on the studies of the
manufacturer.
Regardless of the inherent stability of the binder layer, it is known that good storage conditions will extend the life of
all tapes. While a good storage environment cannot reverse all the degradation that has already occurred, it can
slow down additional deterioration.
NOTE Some degraded tape can be rendered temporarily playable by a variety of specialized procedures.
Two storage conditions are described in this International Standard. Medium-term storage conditions are
recommended for tape with an expected useful life of ten years, while extended-term storage conditions are
intended for tape with an expected life of fifty years. The conditions given in this storage recommendation represent
a compromise between maximizing the tape life, considerations of convenience, and the cost of building and
maintaining a storage facility.
INTERNATIONAL STANDARD ISO 18923:2000(E)
Imaging materials — Polyester-base magnetic tape — Storage
practices
1 Scope
This International Standard provides recommendations concerning the storage conditions, storage facilities,
enclosures, and inspection for recorded polyester-base magnetic tapes in roll form. It covers analog and digital
tape and includes tape made for audio, video, instrumentation and computer use.
This International Standard is applicable to medium-term and extended-term storage of magnetic tape as defined in
3.18 and 3.7 and also is applicable to magnetic-tape records intended as master tapes, which should not be in
frequent use.
Deviations from these recommendations, whether before or after recording, may result in shortened life
expectancy. For example, adverse conditions during shipment, handling, or usage.
This International Standard is not applicable to "work" or "use" copies (see informative annex C).
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
1)
NFPA 75-1995, Electronic computer/Data processing equipment.
1)
NFPA 90A-1996, Installation of air conditioning and ventilating systems.
1)
NFPA 232-1995, Protection of records.
2)
ASHRAE, Equipment. 1988.
2)
ASHRAE, Handbook of fundamentals. 1988.
2)
ASHRAE, Systems. 1987.
1) Available from the National Fire Protection Association, 1 Batterymarch Park, P.O. Box 9101, Quincy, MA 02269-9101,
USA.
2) Available from the American Society of Heating, Refrigeration and Air Conditioning Engineers, 1791 Tullie Circle, NE
Atlanta, GA 30329, USA.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
aperture
window
opening on the flange that is used to facilitate threading of magnetic tape on the hub and inspection of the wind
3.2
base
support in a recording material on which the magnetic layer (and, if necessary, the back layer) is coated
3.2.1
cellulose-acetate base
base for recording materials composed mainly of cellulose esters of acetic acid
3.2.2
polyester base
base for recording materials composed mainly of a polymer of ethylene glycol and terephthalic acid (also referred
to as polyethylene terephthalate), or a polymer of ethylene glycol and 2,6 naphthalene dicarboxylic acid (also
referred to as polyethylene naphthalate)
3.3
cartridge
housing for a roll of recording material, such as photographic film or magnetic tape, attached to a single hub or reel
SEE cassette (3.4).
3.4
cassette
housing for a roll of recording material, such as photographic film or magnetic tape, whose ends are attached to
two hubs or reels
3.5
container
box, can, or carton used for storage and shipping of recording materials
EXAMPLE The box into which a reel, cassette, cartridge or shell is placed is a container.
NOTE Reels, cassettes, cartridges or shells are not containers.
3.6
dew-point
temperature at which moisture begins to condense on a surface, corresponding to saturation for a given absolute
humidity
EXAMPLE The more humid the air, the higher the dew-point temperature.
3.7
extended-term storage conditions
storage conditions suitable for the preservation of information recorded on the majority of magnetic tapes for
50 years
3.8
fire-protective storage
facilities designed to protect records against excessive temperatures, water and other fire-fighting agents, and
steam developed by insulation of safes or caused by the extinguishing of fires and collapsing structures
2 © ISO 2000 – All rights reserved

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