ISO 18920:2000

INTERNATIONAL ISO
STANDARD 18920
First edition
2000-07-15
Imaging materials — Processed
photographic reflection prints — Storage
practices
Matériaux pour image — Tirages photographiques traités par réflexion —
Directives pour l'archivage
Reference number
ISO 18920:2000(E)
©
ISO 2000

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ISO 18920:2000(E)
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ISO 18920:2000(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .2
3 Terms and definitions .2
4 Enclosures and containers.3
5 Storage housings.4
6 Storage rooms.4
7 Environmental conditions.5
8 Fire-protective storage (see annex H) .7
9 Print identification, handling, and inspection (see annexes E, F and I).8
Annex A (informative) Numbering system for related International Standards.9
Annex B (informative) Humidity during storage .10
Annex C (informative) Temperature during storage.11
Annex D (informative) Temperature/relative humidity relationship .12
Annex E (informative) Historic records for photographic prints.13
Annex F (informative) Distinction between storage (record) copies and work (reference) copies .14
Annex G (informative) Air-entrained and gaseous impurities .15
Annex H (informative) Fire protection.16
Annex I (informative) Silver image degradation.17
Bibliography.18
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ISO 18920:2000(E)
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 18920 was prepared by Technical Committee ISO/TC 42, Photography.
This first edition cancels and replaces the fourth edition of ISO 6051 (ISO 6051:1997), and is mainly an editorial
revision.
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 I of this International Standard are for information only.
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ISO 18920:2000(E)
Introduction
Photographic and other reflection prints, including hard-copy output from digital imaging systems, have become
increasingly important as documentary and pictorial reference material in archives, libraries, government,
commerce and academia. This has focused attention on the importance of the preservation of such materials to
ensure their longest possible life.
The stability and useful life of photographic reflection prints depend on their physical and chemical properties and
the processing, as well as on the conditions under which they are stored and used. This International Standard
provides recommendations on proper storage conditions and practices.
The important elements affecting the useful life of photographic reflection prints during storage are as follows:
� relative humidity and temperature of the storage environment;
� hazards of fire, water, and light exposure;
� fungal growth and other micro-organisms;
� contact with certain chemicals in solid, liquid, or gaseous form;
� physical damage.
The extent to which the relative humidity and temperature of the storage environment, or variations of both, can be
permitted to reach beyond recommended limits without producing adverse effects will depend upon the duration of
exposure, biological conditions conducive to fungal growth, and the accessibility of the atmosphere to the print
surfaces.
The term “archival” is no longer used to express longevity or stability in International Standards on imaging
materials since it has been interpreted to have many meanings, ranging from preserving documents “forever”,
which is unattainable, to temporary storage of actively used materials.
This International Standard defines two levels of recommended storage conditions: medium-term and extended-
term. Medium-term storage conditions can be used to preserve information for a minimum of 10 years. Extended-
term storage conditions shall be used when it is desired to preserve information for as long as possible, and these
conditions will prolong the life of all prints, even those not optimized for permanence.
The space requirements and costs for establishing and operating the two levels of storage conditions (medium-
term and extended-term) differ significantly. Furthermore, the specified limits of temperature and relative humidity
for both sets of storage conditions may not be realizable due to budgetary constraints, energy considerations,
climatic conditions, building construction, etc. However, it must be recognized that any deviation from the specified
conditions will reduce the effectiveness of the storage environment. If such deviation is unavoidable, the lowest
possible storage temperature should be provided. In any event, the best preservation of prints will be attained with
extended-term storage conditions.
The recommendations of this International Standard for the storage of photographic reflection prints encompass the
following:
� storage enclosures, housing, and rooms;
� atmospheric and environmental conditions;
� fire protection;
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ISO 18920:2000(E)
� handling and inspection procedures.
With the exception of fire and associated hazards that are sufficiently common to warrant inclusion of protective
measures, this International Standard does not pertain to means or methods for protecting photographic reflection
prints against natural or man-made catastrophes.
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INTERNATIONAL STANDARD ISO 18920:2000(E)
Imaging materials — Processed photographic reflection prints —
Storage practices
1 Scope
1.1 This International Standard specifies dark storage conditions, storage facilities, and procedures for the
handling and inspection of photographic reflection prints of all types and sizes.
1.2 This International Standard is applicable to photographic reflection prints on the following opaque supports:
� fibre-base paper;
� RC (resin coated) paper;
� plastic films (polyester, cellulose acetate, etc.).
1.2.1 This International Standard is applicable to the following black-and-white silver gelatin prints:
� wet-processed, including those that have been chemically treated to improve the permanence of the silver
image and/or to modify its colour (e.g. with gold, selenium or sulfur formulations);
1)
� diffusion transfer (e.g. Polaroid and Fuji Photo Film instant prints );
� stabilization-processed (which contain the silver image as well as invisible, chemically stabilized silver halides);
� heat-processed.
1.2.2 This International Standard is applicable to the following multicolour and monochrome photographic prints:
� chromogenic, washed and stabilized;
� silver dye bleach;
� dye transfer;
1)
� diffusion transfer (e.g. Polaroid and Fuji Photo Film instant prints , peel-apart or integral);
� pigmented gelatin (carbon, carbro, etc.).
1.2.3 This International Standard is applicable to black-and-white and colour photographic reflection prints made
with the following systems:
� thermal dye transfer (commonly referred to as dye sublimation);
1) Polaroid and Fuji Photo Film instant prints are examples of suitable products available commercially. This information is
given for the convenience of users of this International Standard and does not constitute an endorsement by ISO of these
products.
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ISO 18920:2000(E)
� thermal wax transfer;
� electrophotographic;
� ink jet;
� diazo.
1.3 Recommendations for storage of photographic films are given in ISO 18911 and for storage of processed
photographic plates in ISO 18918. Print material on translucent film supports intended to be viewed primarily by
transmitted light should be stored in accordance with ISO 18911.
1.4 This International Standard is applicable to medium-term and extended-term storage conditions as defined in
clause 3.
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.
ISO 14523:1999, Photography — Processed photographic materials — Photographic activity test for enclosure
materials.
2)
ISO 18902:— , Imaging materials — Processed films, plates and papers — Filing enclosures and storage
containers.
2)
ISO 18911:— , Imaging materials — Processed safety photographic films — Storage practices.
ISO 18918:2000, Imaging materials — Processed photographic plates — Storage practices.
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
archival medium
recording material that can be expected to retain information forever, so that such information can be retrieved
without significant loss when properly stored
NOTE There is, however, no such material and it is not a term to be used in International Standards or system
specifications.
3.2
extended-term storage conditions
storage conditions suitable for the preservation of recorded information having a permanent value
2) To be published.
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ISO 18920:2000(E)
3.3
fire-protective storage
facility 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
3.4
fire-resistant vaults
3�
fire-resistant vaults as defined in appropriate national standards and regulations [1, 2]
3.5
insulated record containers (Class 150)
insulated record containers (Class 150) as defined in appropriate national standards and regulations [3, 4]
3.6
life expectancy
LE
length of time that information is predicted to be acceptable in a system at 21�C and 50 % RH
3.7
medium-term storage conditions
storage conditions suitable for the preservation of recorded information for a minimum of 10 years
3.8
storage container
box or can used to store prints
3.9
storage enclosure
any item in close or direct contact with recording material such as folders, envelopes, sleeves, albums and mats
3.10
storage housing
physical structure supporting materials and their enclosures
NOTE It may consist of drawers, racks, shelves or cabinets.
4 Enclosures and containers
All enclosures and containers used for medium-term and extended-term storage shall meet the requirements of
ISO 18902 and ISO 14523. This includes enclosures and containers that are in either direct or indirect contact with
the prints. Photographic reflection prints may be stored in envelopes or sleeves of paper or plastic, file folders,
folding cartons, boxes, and albums, or may be matted. Photographic reflection prints should be protected from
unnecessary light exposure, especially colour and diazo prints which shall not be exposed at all.
Generally, prints smaller than 28 cm� 36 cm in size may be stored vertically, but shall be placed between rigid
supports to minimize slumping and curling. Prints 28 cm� 36 cm or larger should be stored horizontally, unless
mounted on rigid supports. Stacks of horizontal prints should be less than 5 cm high to prevent excessive pressure
on prints at the bottom.
Multiple prints, stored within an enclosure or container, shall be oriented with the emulsion sides against back
sides, never emulsion against emulsion.
3�
The numbers in square brackets refer to references listed in the bibliography.
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ISO 18920:2000(E)
Suitable plastic enclosure materials are uncoated polyester (polyethylene terephthalate), polystyrene, high-density
polyethylene and polypropylene. Other plastics may be satisfactory, but there has been no extended experience
with such materials. Glassine envelopes and chlorinated, nitrated, or highly plasticized sheeting shall be avoided.
Specifically, cellulose nitrate and polyvinyl chloride are not acceptable.
Sealed enclosures shall be used where needed to maintain the desired moisture content of the prints, to protect
against gaseous and solid atmospheric contaminants, or when low-temperature storage is used without humidity
control. Heat-sealed foil bags can provide this protection.
The adhesive used for seams and joints shall also meet the requirements of ISO 18902 and ISO 14523. The filing
enclosure shall be constructed so that the seam or joint will be at the edge of the enclosure and not in contact with
the image layer. Photographic-quality gelatin, modified and photographically inert starch, some acrylic and polyvinyl
acetate adhesives, and methyl cellulose are suitable adhesives for use with paper.
For maximum life, prints shall be in a clean condition before being placed in storage and shall be inspected
periodically thereafter, as outlined in 9.3.
5 Storage housings
Photographic reflection prints should be stored in closable storage housings such as drawers or cabinets, in
storage cabinets with tightly fitting doors, or on open shelves when enclosed inside containers. The storage-
housing materials shall be non-combustible, non-corrosive, and chemically inert, for example, anodized aluminum,
stainless steel, or steel with a non-plasticized synthetic resin-powder coating. Wood, pressboard, particle-board,
plywood, and other such materials shall be avoided because of their combustible nature and the possibility of their
producing active deteriorating agents as they age.
The finish on the storage housing materials shall be durable and shall not contain substances that can have a
deleterious effect on the stored prints. Adverse effects may be produced by finishes containing chlorinated or highly
plasticized resins, or by solvents off-gassing from freshly applied finishes. Paints used on cabinets may give off
peroxides, solvents and other contaminants for up to three months after application. Cabinets made of stainless
steel or anodized aluminum are recommended. Metal housing materials that have been powder-coated (a layer of
resin particles that are electrostatically applied to the surface of the metal and then fused to the surface using heat
without the use of chemical solvents) are also recommended.
When air-conditioned individually, storage housings shall be arranged to permit interior circulation of air to all
shelves and drawers holding print containers, so as to provide uniform humidity conditions. Storage housing
located in rooms conditioned in accordance with 7.2 shall be provided with ventilation openings that permit access
of air to the interior. Such openings shall not interfere with the requirements for fire-protective storage or water
protection.
Different types of prints and films may be stored in the same storage area. However, different types of material
shall not be stored in the same enclosure or storage container. Magnetic tapes or optical disks shall not be stored
in the same storage vault as photographic prints due to the possible deleterious effects.
6 Storage rooms
6.1 Medium-term storage rooms
Rooms and areas used for print storage should be located in the same area as rooms containing provisions for
inspection and viewing of prints. Good housekeeping is essential. Walls and enclosed air-conditioned spaces shall
be designed to prevent condensation of moisture on interior surfaces and within walls, especially during periods of
low exterior temperatures when the walls may be cooled below the dew-point of the air.
Provisions shall be made against damage of prints by water from floods, leaks and sprinklers, and from the steam
released from masonry walls during a fire. A special storage room separated from the work areas for print records
of medium-term interest generally will not be required, provided the conditions recommended in 7.2 are maintained.
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ISO 18920:2000(E)
6.2 Extended-term storage rooms
For extended-term storage, the requirements of 6.1 shall be met. The value of photographic prints kept for long-
term purposes makes it advisable to provide a storage room or vault separate from medium-term storage facilities,
temporary storage facilities, offices or work areas.
7 Environmental conditions
7.1 Introduction
The recommended relative humidity and temperature conditions given in Table 1 shall be maintained either within
individual storage housings or within storage rooms containing such housings.
7.2 Temperature and humidity specifications for storage (see annexes B, C and D)
7.2.1 Medium-term storage environment
The maximum temperature for medium-term storage shall be 25�C. Cycling of temperature shall not be greater
than� 5�C over a 24 h period, and the peak temperature shall not exceed 30�C. Some temperature fluctuation is
allowable as long as the relative humidity stays within the specified limits.
The relative humidity of a medium-term storage environment shall be between 20 % and 50 %, and cycling of
relative humidity shall not be greater than � 10 % over a 24 h period. The moisture content in prints shall not be
greater than the moisture in equilibrium with these relative humidities. Storing prints at the lower limit of the
specified relative humidity range may cause curling of the prints or physical damage during handling (see annex E);
prints may need to be equilibrated to a higher relative humidity prior to use.
7.2.2 Extended-term storage environment
The maximum temperature for extended-term storage shall be as specified in Table 1. Cycling of temperature shall
not be greater than� 2�C over a 24 h period, and some temperature fluctuation is allowable as long as the relative
humidity stays within the specified limits.
The relative humidity of an extended-term storage environment shall be as specified in Table 1. The variation of
relative humidity shall not be greater than � 5 % over a 24 h period. The moisture content in prints shall not be
greater than the moisture in equilibrium with these relative humidities.
For black-and-white silver, silver dye bleach, dye/silver diffusion transfer (instant), dye imbibition (transfer), pigment
and diazo, a maximum storage temperature of 18�C shall be used. Added protection may be obtained for all prints
by low-temperature storage, as such storage improves the stability of both the print support and the image.
For multicolour and monochrome chromogenic dye prints and all other types of prints not specified, a maximum
storage temperature of 2�C shall be used. Excellent keeping behaviour has been obtained by storing colour prints
at such low temperatures. The recommended humidity and temperature conditions may be maintained either within
individual storage housings or within storage rooms containing such housings. Either of the following two methods
may be used in order to prolong the useful life of prints.
a) The first method is to use a storage room controlled at 2�C and maintained within the recommended relative
humidity range. This method alleviates the need for sealed storage containers, but requires expensive
equipment and facilities to maintain the environmental conditions. One problem is the danger of moisture
precipitation on print surfaces when they are brought into a warm room. This can be avoided by placing prints
in sealed moisture-proof containers or in heavy-gauge self-sealing plastic bags prior to removal from the cold
vault and allowing them to warm above the dew-point prior to opening.
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ISO 18920:2000(E)
b) The second method is useful when prints are removed only infrequently from storage. In this method, the
prints are equilibrated with air near the low limit of the specified relative humidity, then sealed in air-tight
containers and placed in cold storage. The required humidity-conditioning period for fibre-base prints is 1 day
and for RC (resin coated) prints is 7 days. Special heat-sealable foil bags are commonly used and double-
bagging (one heat sealed bag within another) can be employed to minimize the problem of air leakage through
tiny holes in the bag material. One advantage of this method is that environmental humidity control is not
needed and relatively low-cost freezers or refrigerators can be used. A disadvantage is the requirement for
reconditioning and rebagging prints to return them to cold storage each time they are removed for
examination.
Very low-humidity conditions may produce brittleness in prints having a gelatin emulsion. In such cases, it is good
practice to restore flexibility prior to use by reconditioning the prints up to a relative humidity not exceeding 50 %.
After use, reconditioning to the recommended humidity is required before returning the prints to sealed containers.
The benefit of low-temperature storage is reduced dramatically when prints are taken out frequently and/or for
extended periods of time into higher temperature environments (see annexes D, E and F).
Table 1 — Maximum temperature and average relative humidity ranges for storage
a
Process Medium-term storage
Extended-term storage
Maximum Relative Maximum Relative
b c d e
temperature humidity range temperature humidity range
�C % �C %
Black-and-white silver 25 20 to 50 18 30 to 50
Silver dye bleach
Dye/silver diffusion
transfer (instant)
Dye imbibition (transfer)
Pigment
Diazo
f
Chromogenic dye 25 20 to 50 2 30 to 40
g
All others 25 20 to 50 � 3 30 to 50
a
Formerly known as “archival storage”, see the introduction. For storage of historic still-photographic prints, see annex E for information.
b
Cycling of temperature shall not be greater than � 5 �C over a 24 h period; the peak temperature shall not exceed 30 �C.
c
Cycling of relative humidity (RH) shall not be greater than � 10 % over a 24 h period.
d
Cycling of temperature shall not be greater than � 2 �C over a 24 h period; the peak temperature shall not exceed the specified
maximum temperatures. No lower temperature limit is specified; however � 20 �C is a practical lower limit when considering the mitigating
effect on life expectancy by time out of storage (see annex D).
e
Cycling of relative humidity shall not be greater than � 5 % over a 24 h period.
f
Generally, stability of chromogenic prints is 10 to 15 times greater when stored at 2 �C compared to room temperature storage. The
extended-term storage conditions specified for chromogenic prints differ from those specified for chromogenic colour film materials. The two
temperature limits specified for prints are also specified for film; the corresponding relative humidity ranges specified for prints are higher due
to potential physical problems such as curl and brittleness. The following environmental conditions meet the recommendations of this
International Standard and ISO 18911 and are suitable for the storage of both types of materials: a maximum temperature of 2 �C and an RH
of 30 % and a maximum temperature of � 3 �C (minus three degrees Celsius) and an RH range of 30 % to 40 %. Older and historic
chromogenic colour print materials are comparatively less stable and may be stored at a colder temperature to increase the life expectancy
of the prints (see annex E).
g
The rates of degradation and the potential for physical problems due to low temperature and/or low relative humidity storage with print
materials using newer technologies, such as thermal wax transfer, thermal dye transfer (commonly known as dye sublimation),
electrophotographic colour, and ink jet, are currently unknown.
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ISO 18920:2000(E)
7.3 Environmental conditioning requirements
Properly controlled air-conditioning may be necessary for maintaining humidity and temperature within the specified
limits, particularly for extended-term storage where the requirements are more stringent than those for medium-
term storage. Slightly positive air pressure should be maintained within the storage room or vault. Air-conditioning
installations and automatic fire-control dampers in ducts carrying air to or from storage vaults shall be constructed
and maintained on the basis of recommendations contained in appropriate national standards and regulations
[5, 6]. They shall also follow recommendations for fire-resistant file rooms contained in appropriate national
standards and regu
...