ISO 18920:2011

INTERNATIONAL ISO
STANDARD 18920
Second edition
2011-10-01
Imaging materials — Reflection prints —
Storage practices
Matériaux pour l’image — Tirages par réflexion — Directives pour
l’archivage
Reference number
ISO 18920:2011(E)
©
ISO 2011

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ISO 18920:2011(E)
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© ISO 2011
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ISO 18920:2011(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 . 3
6 Storage rooms . 4
6.1 Medium-term storage rooms . 4
6.2 Extended-term storage rooms . 4
7 Environmental conditions . 4
7.1 Temperature and humidity specifications for storage . 4
7.2 Environmental conditioning requirements . 7
7.3 Air purity . 8
7.4 Light, use, and display . 8
8 Fire-protective storage . 9
9 Print identification, handling and inspection . 9
9.1 Identification . 9
9.2 Handling . 9
9.3 Inspection . 9
Annex A (informative) Humidity during storage . 11
Annex B (informative) Temperature during storage .12
Annex C (informative) Temperature/relative humidity relationship .13
Annex D (informative) Distinction between originals and copies made for active use .14
Annex E (informative) Air-entrained and gaseous impurities .16
Annex F (informative) Fire protection .17
Annex G (informative) Silver and colour image degradation.18
Annex H (informative) Cold storage practices .19
Annex I (informative) Print stability .20
Bibliography .22
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ISO 18920:2011(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 2.
The main task of technical committees is to prepare International Standards. 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 document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 18920 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18920:2000), which has been technically revised.
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ISO 18920:2011(E)
Introduction
This International Standard is one of a series of standards dealing with the physical properties and stability of
imaging materials.
Photographic and other reflection prints, including hard-copy output from digital imaging systems, have
become increasingly important as documentary and pictorial reference material and art for consumers, as well
as in archives, libraries, government, commerce, museums and academia. This has focused attention on the
importance of preserving such materials to ensure their longest possible life.
The stability and useful life of reflection prints (hereafter referred to as prints) depend on their physical and
chemical properties, 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 prints during storage are as follows:
a) relative humidity and temperature of the storage environment;
b) hazards of fire, water and light exposure;
c) fungal growth and other micro-organisms;
d) contact with certain chemicals in solid, liquid or gaseous form;
e) physical damage;
f) proper processing;
g) enclosures and containers in contact with the print material.
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 can be used when it is desired to preserve information for as long as possible; 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 ability to maintain specified limits of temperature
and relative humidity for both sets of storage conditions can be limited due to budgetary constraints, energy
considerations, climatic conditions, building construction, etc. However, any deviation from the specified
conditions will reduce the effectiveness of the storage environment. If such deviation is unavoidable, it is
advisable to select the lowest possible storage temperature that can be maintained. In any event, the best
preservation of prints will be attained with extended-term storage conditions.
This International Standard does not address the various strategies to upgrade substandard environments.
However, institutions with substandard environments and restricted budgets can plan for the improvement
of these environments as resources allow by judicious use of air conditioning, dehumidifiers (or humidifiers),
air circulation and filtration. Although practicalities might force compromises, any improvement in poor
conditions will add to the longevity of materials, even if they do not attain the life expectancies possible with
the environments recommended in this International Standard. The subject of basic air conditioning principles,
the various options and associated costs are outside the scope of this International Standard. There are many
references on this subject.
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ISO 18920:2011(E)
The storage of traditional paper collections is not within the scope of this International Standard. However,
many archives containing mixed recording media also include such collections. Archivists are encouraged to
review the appropriate standards for those materials specified in ISO 11799 and in the International Standards
listed in Clause 2.
The recommendations of this International Standard for the storage of prints encompass the following:
— storage enclosures, housing and rooms;
— atmospheric and environmental conditions;
— fire protection;
— 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.
It is understood that the archivist of a multiple media collection might be forced to limit the number of storage
environments that can be provided. This compromise might be based on the value, physical size, quantity or
legal requirements to maximize life expectancy of some collections relative to others. The issues of mixed
media archives and recommendations for their storage are addressed in ISO 18934.
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INTERNATIONAL STANDARD ISO 18920:2011(E)
Imaging materials — Reflection prints — Storage practices
1 Scope
This International Standard specifies dark storage conditions, storage facilities and procedures for the handling
and inspection of reflection prints of all types and sizes.
This International Standard is applicable to prints on the following opaque supports:
a) fibre-base paper;
b) RC (resin coated) paper;
c) pigmented and other types of plastic supports, e.g. polyester, cellulose acetate;
d) fabric, e.g. canvas, linen.
This International Standard is applicable to the following processed black-and-white silver gelatine prints:
1) 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 sulphur formulations;
1)
2) diffusion transfer, e.g. Polaroid and Fuji Photo Film instant prints ;
3) stabilization-processed (which contain the silver image as well as invisible, chemically stabilized
silver halides).
This International Standard is applicable to the following processed multicolour and monochrome colour
photographic prints:
i) chromogenic, washed and stabilized;
ii) silver dye bleach;
iii) dye transfer;
1)
iv) diffusion transfer, e.g. Polaroid and Fuji Photo Film instant prints , peel-apart or integral;
v) pigmented gelatine, e.g. carbon, carbro.
This International Standard is applicable to black-and-white and colour prints made with the following systems:
— thermal dye transfer (commonly referred to as dye sublimation);
— thermal wax transfer;
— electro-photographic;
— dye and pigmented ink jet;
— swellable and porous-coated media supports;
— diazo.
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 18920:2011(E)
Recommendations for storage of photographic films and storage of processed photographic plates are given
in ISO 18911 and ISO 18918 respectively.
This International Standard is applicable to medium-term and extended-term storage conditions, as
defined in Clause 3.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
ISO 18902, Imaging materials — Processed imaging materials — Albums, framing and storage materials
ISO 18916, Imaging materials — Processed imaging materials — Photographic activity test for enclosure materials
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
extended-term storage conditions
storage conditions suitable for the preservation of recorded information which has permanent value
3.2
fire-protective storage
facility designed to protect records against excessive temperatures, water and other fire-fighting agents, and
against steam developed by insulation of safes or caused by the extinguishing of fires and collapsing structures
3.3
fire-resistant vaults
fire-resistant vaults as defined in appropriate national standards and regulations
NOTE See References [9] and [17].
3.4
insulated record containers (Class 150)
insulated record containers (Class 150) as defined in appropriate national standards and regulations
NOTE See References [7] and [12].
3.5
life expectancy
LE
length of time that information is predicted to remain in an acceptable state when placed in a system at
21 °C and 50 % RH
NOTE In the past, the term “archival” was used to define material that could be expected to preserve images forever,
so that such images could be retrieved without significant loss when properly stored. However, as no such material
exists, this is now a deprecated term and is no longer used in International Standards for imaging materials or in systems
specifications.
3.6
medium-term storage conditions
storage conditions suitable for the preservation of recorded information for a minimum of 10 years
3.7
storage container
box or can be used to store prints
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ISO 18920:2011(E)
3.8
storage enclosure
any item in close or direct contact with recording material, such as folders, envelopes, sleeves, albums and mats
3.9
storage housing
physical structure supporting materials and their enclosures
NOTE This can 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 18916. This includes enclosures and containers that are in either direct or indirect
contact with the prints. Prints may be stored in envelopes or sleeves of paper or plastic, file folders, folding
cartons, boxes and albums, or may be matted. Prints shall be protected from unnecessary use and light
exposure. Prints that are prone to light-induced fading, especially diazo and some colour processes, 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.
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. Glassine is not
dimensionally stable when exposed to high relative humidity, although it may meet the other requirements
specified in ISO 18902 and pass the photographic activity test.
Microclimates (sealed enclosures or cabinetry) shall be used where needed in order to maintain the desired
moisture content of the prints where humidity control is inadequate in storage rooms or where cold storage vaults
and units do not have humidity control, and to protect against gaseous and solid atmospheric contaminants.
A variety of sealed vapour-proof housings, containers and cabinetry can provide this protection (as discussed
in Table 1, 7.1.3.2 and Annex H).
The adhesive used for seams and joints shall also meet the requirements of ISO 18902 and ISO 18916. 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 gelatine, 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
Prints shall 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, e.g. anodized aluminium, 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. Finishes containing chlorinated or highly plasticized resins, or solvents
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ISO 18920:2011(E)
giving off gas from freshly applied finishes can adversely affect the image and base layers on prints. 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 aluminium are recommended. Metal housing materials that have
been powder-coated (a layer of resin particles that are applied electro-statically 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 7.1 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, films and other media may be stored in the same storage room separately from each other.
However, different types of material shall not be stored (interfiled) within the same enclosure or storage container.
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 fire and by water from floods, leaks and sprinklers, and from
[7][9][12][17]
the steam released from masonry walls during a fire . Storage rooms or vaults should be located above
basement levels where possible. A special storage room separated from the work areas for prints of medium-
term interest generally will not be required, provided the conditions recommended in 7.1.2 are maintained.
6.2 Extended-term storage rooms
For extended-term storage, the requirements of 6.1 shall be met.
In addition, 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 Temperature and humidity specifications for storage
7.1.1 General
See Annexes A, B, C, H and I.
The recommended temperature and relative humidity conditions in Table 1 shall be maintained either within
individual storage housings or within rooms containing such housings.
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ISO 18920:2011(E)
Table 1 — Maximum temperature and average relative humidity ranges for storage
a
Medium term storage Extended term storage
Relative Relative
Maximum Maximum
ag
Print process humidity humidity
c
temperature temperature
bd
range range
°C % RH °C % RH
e
Black-and-white silver 25 20 to 50 16 30 to 50
Pigment (carbon, carbro)
Dye imbibition (dye transfer)
Silver dye bleach
Dye/silver diffusion transfer (instant)
Diazo
f
Electro-photographic
f
Thermal dye transfer (dye sublimation) 25 20 to 50 2 30 to 50
Chromogenic dye 5 30 to 40
fh
Ink jet (dye or pigment)
a
The values of Table 1 are the required conditions experienced by the photographic material. When micro-climates (housings or
storage containers) are used that establish internal climate conditions, the environment of the exterior room need not necessarily meet
the Table 1 conditions. See Annex H.
b
As discussed in 7.1.3.3, certain gelatine emulsion photographs can be sensitive to RH levels of less than 30 % and can experience
physical changes that can exacerbate existing deterioration such as flaking, cracking and curl. If these materials are present and
RH above 30 % cannot be maintained, then microclimate storage housings or cabinetry shall be used to protect photographs from
extremes in cycling or prolonged excursions below 30 %. Alternatively, a higher RH set point can be selected, e.g. 35 %, when a 5 %
RH fluctuation within any 24-hour period does not exceed the lower RH limit of 30 %.
c
Cycling of temperature shall not be greater than ± 2 °C over any 24-hour period. Some prints can become brittle at low temperatures
and require careful handling when cold to avoid flexing that could cause cracks and image delamination (refer to 7.1.3.3).
d
Cycling of relative humidity shall not be greater than ±5 % RH over any 24-hour period. However, the relative humidity shall not
exceed 50 % RH. If RH cycling in the room cannot be controlled to this level, then microclimate storage housings or cabinetry shall be
used to protect photographs from extremes in cycling or prolonged excursions to either high or low RH.
e
If there is concern about the possibility of silver image deterioration due to atmospheric pollutants, poor quality enclosures,
and/or excessively high temperature and humidity levels, a post-process chemical conversion treatment can be used to provide added
protection (see ISO 18915).
f
The rates of degradation and the potential for physical problems with extremely low temperature and/or low relative humidity
storage is not well known for rapidly changing technologies such as thermal dye transfer (dye sublimation), thermal wax transfer,
electro-photographic, and the many different ink jet image media (dye, pigment, wax) and base media (porous, swellable, plain paper).
Factors such as chemical sensitivity, humidity fastness, and the stability of base materials may have a greater impact on longevity than
thermal stability and light-fastness.
g
Print life expectancy ratings by process type are not provided in this International Standard. For information on print stability, see
Annex I.
h
Some current ink jet prints, especially those utilizing inks made from stable pigment or optimized dyes printed onto stable
supports as recommended by the manufacturer, may have very good image stability at temperatures warmer (up to 16 °C) than the
recommended cold storage temperatures listed for extended-term storage. Where the identification of the type of ink and base cannot
be determined, or where stable ink jet prints may have been interfiled with less stable materials, the colder temperatures listed shall
be used unless prints can be separated by type for storage at different temperatures. The use of non-permanent paper supports or
papers that are not optimized for the particular ink set can also adversely affect the overall stability of the print, requiring storage at
cold temperatures.
7.1.2 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 any 24-hour period, and the peak temperature shall not exceed 30 °C. Some temperature
fluctuation is permitted 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 %. Cycling of
relative humidity shall not be greater than ±10 % over any 24-hour period within the specified range (relative
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ISO 18920:2011(E)
humidity shall not exceed 50 %). 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 7.1.3.3); prints may need to be
equilibrated to a higher relative humidity prior to use.
7.1.3 Extended-term storage environment
7.1.3.1 Recommended environments for specific print media
A maximum storage temperature of 16 °C with a set point RH within the given range listed in Table 1 shall be
used for black-and-white silver gelatine, silver dye bleach, dye/silver diffusion transfer (instant), dye imbibition
(transfer), pigment (carbon, carbro) and diazo.
Cool storage between 2 °C and 5 °C with a set point RH within the range listed in Table 1 shall be used for
monochrome and multi-colour chromogenic, thermal dye transfer (dye sublimation) and ink jet (see Annex H
for cold storage practices). Excellent keeping behaviour has been obtained by storing colour prints at such low
temperatures.
7.1.3.2 Impact of environment on media longevity
See Annexes C and H.
The rate of most chemical reactions
...