ISO 18911:2010

INTERNATIONAL ISO
STANDARD 18911
Second edition
2010-09-01
Imaging materials — Processed safety
photographic films — Storage practices
Matériaux pour l'image — Films photographiques de sécurité traités —
Techniques d'archivage
Reference number
©
ISO 2010
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©  ISO 2010
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ii © ISO 2010 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
0.1 General .v
0.2 Nature of the photographic film.v
0.3 Photographic processing of the film.v
0.4 Storage conditions .v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Film enclosures .3
4.1 Requirements.3
4.2 Film in roll format .3
4.3 Film in sheet and slide format.4
5 Storage housings .5
6 Storage rooms .5
6.1 Medium-term storage rooms.5
6.2 Extended-term storage rooms .5
7 Environmental conditions .6
7.1 Temperature and humidity specifications for storage .6
7.2 Air-conditioning requirements.9
7.3 Air purity.10
7.4 Light.10
8 Fire-protective storage.10
9 Film identification, handling and inspection .11
9.1 Identification .11
9.2 Handling .11
9.3 Inspection.11
Annex A (informative) Distinction between storage (record) copies and work (reference) copies .12
Annex B (informative) Advantages and disadvantages of protective (sealed) enclosures .14
Annex C (informative) Air-entrained and gaseous impurities .15
Annex D (informative) Humidity during storage .16
Annex E (informative) Temperature during storage.17
Annex F (informative) Temperature/relative humidity relationship .18
Annex G (informative) Microenvironments .20
Annex H (informative) Silver image degradation.21
Annex I (informative) Fire protection .22
Bibliography.23

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 18911 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18911:2000), which has been technically
revised.
This International Standard is one of a series of International 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 ISO 18900 to ISO 18999.
iv © ISO 2010 – All rights reserved

Introduction
0.1 General
The value of records used in archives, museums, libraries, government, commerce and universities has
focused attention on the care of these records to ensure their longest possible life (see References [1][2][3]).
Photographic film is an important documentary and pictorial material, and there is a recognized need for
information on safeguarding photographic film having legal, scientific, industrial, artistic or historical value.
Films are susceptible to degradation from many sources. These factors can be divided into three general
categories as described below.
0.2 Nature of the photographic film
The stability of photographic film records depends on the physical and chemical nature of the film. The
specification for safety photographic film which is suitable for storage is described in ISO 18906.
For preservation purposes, processed photographic films are classified according to their life expectancy (LE)
or LE designation. These are specified in the appropriate International Standards. The term “archival” is no
longer specified to express longevity or stability in International Standards on imaging materials, since it has
been interpreted to have many meanings that range from “preserving information forever” (which is
unattainable) to “temporary storage of actively used information”.
For optimum preservation of photographic information, it is advisable that a high LE film be used and that it be
stored under extended-term storage conditions. A film material suitable for preservation is silver-gelatine-type
film on polyester base that meets the requirements of ISO 18901. However, this International Standard also
applies to processed colour, diazo (see ISO 18905), vesicular (see ISO 18912) and thermally processed silver
(see ISO 18919) films. Although these film types sometimes do not have as high an LE designation, excellent
keeping properties have been obtained with many of them.
0.3 Photographic processing of the film
For black-and-white silver-gelatine-type film, ISO 18901 specifies a maximum residual thiosulfate level for
different LE classifications and a residual silver compounds level.
For diazo film, ISO 18905 specifies a proper development test. ISO 18912, for vesicular film, includes both a
proper development test and a residual diazonium salt test.
0.4 Storage conditions
The conditions under which safety photographic film records are stored are extremely important for the
preservation of film and are the subject of this International Standard (see also ISO 18906). The same
environmental conditions are advisable for nitrate-base films, but it is advisable that they be stored in a
separate storage area having suitable fire protection safeguards (see Reference [4]).
The important elements affecting preservation of processed film are humidity, temperature and air pollutants,
as well as the hazards of fire, water, light, fungal growth, insects, microbiological attack, contact with certain
chemicals in solid, liquid or gaseous form, and physical damage. Direct contact with other generic types of film
can be detrimental to either film.
The extent to which humidity, temperature and atmospheric contaminants, or variations thereof, can be
permitted to reach beyond recommended limits without producing adverse effects will depend upon the
duration of exposure, the biological conditions conducive to fungal growth, and the accessibility of this
atmosphere to the emulsion and support surfaces. Exposure to high temperatures, and in particular to high
humidities, can lead to degradation of the film support and the photographic emulsion (see
References [5][6][7]). Cellulose ester-base films are more subject to base degradation than polyester-base
films.
There are two levels of storage conditions:
⎯ medium-term, and
⎯ extended-term.
Medium-term storage can be used for films where the information is to be preserved for a minimum of
10 years, while extended-term storage conditions can extend the useful life of a majority of freshly processed
films to 500 years. However, extended-term storage conditions will prolong the life of all films, independent of
age, type or processing conditions. The storage protection provided by each level will differ in degree, as will
the cost of providing and maintaining the storage facility.
Immediate availability of space and cost often need to be considered when selecting storage conditions. It is
recognized that many facilities will not be able to obtain the low humidity and low temperature levels specified
in this International Standard because of energy considerations, climate conditions or building construction.
Such deviation from the specified conditions will reduce the degree of protection offered, and in such cases
maintaining a humidity and temperature as low as possible will still provide some benefits.
This International Standard is not designed to provide protection against natural or man-made catastrophes,
with the exception of fire and associated hazards, which are sufficiently common to warrant inclusion of
protection measures.
In addition to the recommendations in this International Standard, good storage practices consider filing
enclosures. These are covered in ISO 18902 and ISO 18934.

vi © ISO 2010 – All rights reserved

INTERNATIONAL STANDARD ISO 18911:2010(E)

Imaging materials — Processed safety photographic films —
Storage practices
1 Scope
This International Standard provides recommendations concerning the storage conditions, storage facilities,
handling and inspection for all processed safety photographic films in roll, strip, aperture-card or sheet format,
regardless of size.
This International Standard is applicable to extended-term and medium-term storage of photographic film.
This International Standard is applicable to photographic film records intended as storage copies, which are
not in frequent use. It does not apply to “work” or “use” copies (see Annex A).
This International Standard, while intended for materials that are properly processed, is also of considerable
value in prolonging the useful life of photographic film whose processing conditions are unknown, or which
has been toned or retouched, or has markings with materials of uncertain or unknown stability.
This International Standard is applicable only to safety photographic film (see ISO 18906). Nitrate-base films
are not covered by this International Standard.
NOTE Nitrate-base films are hazardous (see Reference [8]). They require special storage considerations (see
Reference [4]), but the environmental conditions specified in this International Standard are applicable.
The storage of photographic prints and photographic plates requires different considerations. They are not
covered in this International Standard, but are described respectively in ISO 18920 and ISO 18918.
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 18906, Imaging materials — Photographic films — Specifications for safety film
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
duplicate
reproduction of a master, retaining the same polarity and size
3.2
extended-term storage conditions
storage conditions suitable for the preservation of recorded information on the majority of freshly and properly
processed photographic films for 500 years
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
life expectancy
LE
length of time that information is predicted to be acceptable 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.
3.5
LE designation
rating for the life expectancy (3.4) of recording materials and associated retrieval systems
NOTE The number following the LE symbol is a prediction of the minimum life expectancy, in years, during which
information can be retrieved without significant loss when stored at 21 °C and 50 % RH, e.g. LE-100 indicates that
information can be retrieved after at least 100 years' storage.
3.6
macroenvironment
atmospheric conditions (temperature, relative humidity and pollutants) in a large area in which records are
kept
3.7
medium-term storage conditions
storage conditions suitable for the preservation of recorded information for a minimum of 10 years
3.8
microenvironment
atmospheric conditions (temperature, relative humidity and pollutants) inside a storage enclosure in which
records are kept
3.9
open enclosure
enclosure that is intended for physical protection against mechanical damage, but is neither light-tight nor
airtight
EXAMPLE Reels; cores; spools; cassettes; magazines; folders; envelopes; cartons; boxes; sleeves; transparency
mounts; aperture cards.
3.10
protective enclosure
impermeable sealed container used for protection from outside factors such as reactive gases and moisture,
including changes in relative humidity, and from light for certain kinds of products
EXAMPLE Taped cans; sealed envelopes.
NOTE Protective enclosures sometimes also need to be opaque.
2 © ISO 2010 – All rights reserved

3.11
safety photographic film
photographic film
safety film
film that meets the flammability specifications defined in ISO 18906
3.12
storage housing
physical structure supporting materials and their enclosures
NOTE Storage housing can consist of drawers, racks, shelves or cabinets.
4 Film enclosures
4.1 Requirements
All enclosures used for medium-term and extended-term storage shall meet the requirements of ISO 18902.
Safety photographic film shall comply with the flammability specifications defined in ISO 18906.
4.2 Film in roll format
4.2.1 Medium-term storage enclosures
Aerial film, microfilm, motion-picture film, and some portrait films are wound on reels or cores and stored in roll
form. The rolls shall all be wound tightly, but not under extreme tensions. A tension caused by 0,3 N of pull-out
force for a 35 mm film width is recommended. Rolls greater than 150 m in length shall be stored so that the
radius of the roll is in the horizontal position and the film is supported on its edges. Rolls less than 150 m in
length may also be stored with the radius of the roll in the vertical position, if the core itself is supported by a
horizontal spindle inserted into the cores so as to avoid pressure on the bottom of the roll. However, if such
rolls are on reels or spools which have flanges, a spindle is not required since the flanges support the weight
of the roll.
Motion-picture prints shall be wound with the emulsion surface on the inside of the roll, as this improves
subsequent projection performance (see Reference [9]).
Rolls of photographic film shall be stored in closed containers to provide protection against dirt and physical
damage, unless the film is protected by the storage housing (see Clause 5).
Colour, diazo and thermally processed silver films shall be stored in closed, opaque enclosures or be
otherwise protected from light exposure. Suitable enclosures are containers with telescoping, slip-type, or
threaded twist-on lids. The materials used shall meet the same requirements as those for cores and reels.
Closed enclosures are not necessarily airtight and may provide limited access to ambient air. Therefore, if
they are used, the humidity of the ambient air shall not exceed the recommended limits.
Protective enclosures made from impermeable materials shall be used, where needed, to maintain the
humidity limits of the film (see Clause 7), to protect against gaseous impurities in the atmosphere, or when
low-temperature storage is used without humidity control (see Annex C). Suitable enclosures are closed
containers with friction-type or threaded, twist-on lids having an incorporated seal. Rubber gaskets shall not
be used. Cans within heat-sealed foil bags also provide protection from high humidity.
Metal containers provide the best protection against gases from the environment. However, they may corrode
1)
from acidic fumes from within the container unless they are protected with an overcoat. Alternative materials
are polystyrene, polyethylene and polypropylene.
4.2.2 Extended-term storage enclosures
For extended-term storage, the requirements of 4.2.1 shall be met. The materials used for reels, cores and
containers shall meet the requirements of ISO 18902 and ISO 18916. Rubber bands shall not be used for
confining film on reels or cores. If paper bands are used, the paper shall meet, as a minimum requirement, the
specifications described in ISO 18902 and ISO 18916. Films on reels may be confined by tucking the film end
between the roll and the flange. Pressure-sensitive tape, if needed for the enclosure, shall be free from
peroxide and pass the photographic activity test specified in ISO 18916. Pressure-sensitive tape shall not be
used in contact with the film.
Films may have possible interactions with other films that are of a different generic type (for example, diazo
and silver-gelatine), as well as with magnetic tapes and optical discs. Films of a different generic type shall not
be wound in the same rolls or stored in the same enclosures. Closed containers are required, unless the
photographic film is protected from dirt and damage by the storage housing (see Clause 5).
4.3 Film in sheet and slide format
4.3.1 Medium-term storage enclosures
Film in sheet form may be stored in envelopes of paper or plastic foil, folding cartons, boxes, file folders,
aperture cards, or film strip jackets. Photographic slides may be stored in cardboard, metal or plastic boxes.
Colour, diazo and thermally-processed silver films shall be stored in opaque envelopes or folders, or
otherwise protected from light exposure. Films should not be stacked, as this could cause excessive pressure
on the lowermost sheets. When in direct contact with the surface of the photographic film, the paper or plastic
material used for envelopes, sleeves, jackets, folders, boxes and cartons shall meet, as a minimum
requirement, the specifications described in ISO 18902 and ISO 18916.
Suitable plastic enclosure materials are uncoated polyester (polyethylene terephthalate), polystyrene,
polyethylene and polypropylene. Glassine envelopes and chlorinated, nitrated or highly plasticized sheeting
shall be avoided. Specifically, cellulose nitrate and polyvinyl chloride are not acceptable.
Protective enclosures shall be used, where needed, to maintain humidity within the limits recommended for
the specific film type (see Clause 7), to protect against gaseous impurities in the atmosphere, or when low-
temperature storage is used without humidity control. Heat-sealable envelopes, consisting of aluminium foil
extrusion coated with clear polyethylene on the inside and laminated to a suitable paper sheet on the outside,
have been successfully used as sealed enclosures. Precautions should be taken in handling these envelopes,
so that they are not punctured. To provide greater protection against pinholes, a double bagging technique is
recommended.
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 any seam or joint will be at the edge of the enclosure and not in
contact with the image layer.
Any film that is actively releasing acidic fumes shall be stored in plastic or acid-neutralizing envelopes.
4.3.2 Extended-term storage enclosures
For extended-term storage, the requirements of 4.3.1 shall be met except that film shall not be stored in
cardboard enclosures.
1) Some vesicular films give off acidic fumes that may interact with silver, diazo or dye-gelatine-type films. Decomposing
acetate-base films release acetic acid, which further catalyses base degradation.
4 © ISO 2010 – All rights reserved

Photographic-quality gelatine, modified and photographically inert starch, some acrylic and polyvinyl acetate
adhesives and methyl cellulose are suitable for use with paper storage enclosures. Pressure-sensitive
(permanently tacky) adhesives shall meet the specifications of ISO 18902 and ISO 18916.
Films may have possible interactions with other films that are of a different generic type (for example, diazo
and silver-gelatine), as well as with magnetic tapes and optical discs. Films of different generic types shall not
be interfiled or be in physical contact.
5 Storage housings
Photographic film should be stored in closable housings, such as drawers or cabinets, or on shelves and
racks enclosed by tightly fitting doors in order to provide protection from dust and dirt. Alternatively, open
shelves and racks may be used if the film is in closed containers. The storage housing materials shall be non-
corrosive as described in ISO 18902. They shall also be non-combustible and chemically inert. Wood,
pressed-board, particle-board, plywood and other such materials shall be avoided due to their combustible
nature and the possibility of producing active deteriorating agents as they age.
The finish on storage housing materials shall be durable and should not contain substances that can have a
deleterious effect on stored photographic film. 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 being applied.
Metal housing materials that have been powder coated (a solvent-free finish process in which electrostatically
applied resin particles are fused by heat) or cabinets made from stainless steel or anodized aluminium are
recommended.
When air-conditioned individually, storage housings shall be arranged to permit interior circulation of air to all
shelves and drawers holding film containers so as to provide uniform humidity conditions. Storage housings,
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.
Films and other materials that release acidic fumes, magnetic tapes and optical discs shall not be stored in the
same storage housing as other photographic products.
6 Storage rooms
6.1 Medium-term storage rooms
Rooms and areas used for film storage should be located in the same area as rooms containing provisions for
inspection and viewing of the film. 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 can be cooled below the dew-point of the air.
Provisions shall be made against damage of film by water from floods, leaks, sprinklers and from 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 film records of medium-term
interest, generally will not be required, provided that the conditions recommended in 7.1.2 are maintained.
Films that are not essentially free from release of acidic fumes, such as some vesicular films, shall be stored
in separate storage rooms. Films showing any sign of chemical degradation, such as the presence of acidic
fumes, shall be stored in a separate storage room having a separate circulating-air system.
6.2 Extended-term storage rooms
For extended-term storage, the requirements of 6.1 shall be met.
The value of photographic film 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. Storage
rooms for films that are not essentially free from acid release shall have a separate circulating-air system (see
Annex D).
Storage rooms have been constructed in caves and mines and have proven very satisfactory when
requirements are met for environmental conditions (see 7.1) and air purity (see 7.3).
7 Environmental conditions
7.1 Temperature and humidity specifications for storage
See Annexes D, E and F.
7.1.1 Recommended temperature and relative humidity
The recommended temperature and relative humidity conditions given in Table 1 shall be maintained either
within individual storage housings or within storage rooms containing such housings.
Table 1 — Maximum temperatures and relative humidity ranges for extended-term storage
Maximum Relative humidity
a,b a,c
temperature range
Image Base
°C %
2 20-50
d e
Black-and-white silver-gelatine (see ISO 18901) Cellulose esters 5 20-40
7 20-30
d
Black-and-white silver-gelatine (see ISO 18901)
Thermally or processed silver (see ISO 18919)
Polyester 21 20-50
Vesicular (see ISO 18912)
Silver dye bleach
-10 20-50
e
Colour (chromogenic) Cellulose esters
-3 20-40
Diazo (see ISO 18905) Polyester 2 20-30
NOTE ISO 18934 covers the storage of multiple types of media in a mixed archive.
a
See Annex F for storage of historic still photographic records.
b
Cycling of temperature shall not be greater than ± 2 °C over any 24 h period.
c
Cycling of relative humidity shall not be greater than ± 5 % RH (for example 30 % RH to 40 % RH) over any 24 h period, and shall
not be less than the lower RH limit or greater than the upper RH limit specified in this table.
d
If there is concern about the possibility of silver image oxidation due to atmospheric contaminants, 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).
e
This includes cellulose triacetate, cellulose acetate butyrate and cellulose acetate propionate.

6 © ISO 2010 – All rights reserved

7.1.2 Medium-term storage environment
The average relative humidity (RH) of a medium-term storage environment shall not exceed 50 % RH and the
maximum relative humidity shall not exceed 60 % RH. Ideally, the maximum temperature for extended periods
should not exceed 25 °C, and a temperature below 21 °C is preferable. The peak temperature for short time
periods shall not exceed 32 °C.
Short-term cycling of temperature shall be avoided. Cycling of relative humidity shall not be greater than
± 10 % RH (e.g. 25 % RH to 45 % RH) over a 24 h period. Cycling of temperature shall not be greater
than ± 5 °C over a 24 h period.
Protection may be increased by storing film at low temperature and low relative humidity.
7.1.3 Extended-term storage environment
7.1.3.1 General
When considering extended term storage the impact of low relative humidity conditions shall be taken into
consideration. Low relative humidities can cause excessive contraction or brittleness, or both, in gelatine
emulsions resulting in high curl and an associated risk of handling damage (cracking). Low relative humidities
can cause serious problems with gelatine emulsion layers that have existing physical damage such as cracks
or flaking emulsion layers. With such damaged emulsions, a low relative humidity condition can exacerbate
lifting along cracks and existing areas of flaking and curl. In facilities where such films are stored, care should
be exercised when choosing the relative humidity level so that items in poor condition (those that are curled or
have cracking or delaminating emulsions) are not physically stressed by low relative humidities in the range of
20 % to 30 %. Cycling between low relative humidity areas and higher relative humidity areas can exacerbate
existing problems. If films with the above condition problems are in the collection, the RH set point and RH
cycling should be considered to avoid these low humidities. If this cannot be accomplished then microclimate
storage housings or cabinetry shall be used to protect films from extremes in cycling or prolonged excursions
below 30 %. In general, films stored tightly packed in boxes or albums, or sleeved in plastic, respond slowly to
exterior short-term RH cycling. Loose or bare films, or those stored in partially filled permeable containers,
may experience RH changes more quickly and respond accordingly by undergoing curl and by contraction or
strain on the emulsion (especially along cracks or flaking areas). Storage at low temperature, or at low relative
humidity, or at low temperature and low humidity, can embrittle emulsion or image layers, making them more
susceptible to physical damage during handling. Flexing or rough handling may damage brittle emulsions, in
addition to potentially exacerbating physical problems such as cracking image layers. Because of this, all such
films, especially those in poor condition, should be handled carefully when in storage at low temperature, or at
low relative humidity, or at low temperature and low humidity. In such cases, it is good practice to restore
flexibility prior to use by reconditioning the films up to a relative humidity not exceeding 50 %. After use,
reconditioning to the recommended humidity is required before returning the films to their storage environment.
Copies should be made for items that require frequent or extended use. This is especially true since the
benefits of increased chemical stability of photographic materials gained by storage at low temperature or low
relative humidity are quickly mitigated by frequent cycling and prolonged removal to higher temperatures and
humidities.
7.1.3.2 Recommended environment for black-and-white films
The rate of most chemical reactions, such as the degradation of film base and the discolouration of the image
silver by oxidation, is lowered with decreasing temperature and decreasing relative humidity. Consequently,
life expectancy is increased as either storage temperature or storage humidity is lowered. Moreover, a lower
storage temperature can compensate for a higher humidity to provide the same life expectancy. For this
reason, several relative humidity/temperature combinations can be used for an extended-term storage
environment as specified in Table 1.
Higher relative humidity ranges can be employed if the average temperature is reduced, but the maximum
relative humidity shall not exceed 50 %. Cycling of relative humidity shall be no greater than ± 5 % RH over a
24 h period. Cycling of temperature shall be no greater than ± 2 °C over a 24 h period.
An alternative procedure to controlling the macroenvironment is to condition the film to the recommended
relative humidity at room temperature, place it in hermetically sealed or taped containers, and then put it in
cool storage (see Reference [10]). Roll and sheet films generally are protected adequately against moisture
when placed within two heat-sealed foil bags from which as much air as possible has been expelled before
sealing. Roll films are provided with greater physical protection if first placed in cans. The double-bag
arrangement reduces the possibility of air leakage through pin holes, but does not guarantee it. However,
except in rare instances, it does provide the desired moisture conditions inside the inner bag and, therefore,
permits the use of cold storage vaults or reasonably priced deep-freeze units. It is essential to limit, as much
as possible, the volume of free air in the sealed film container.
It is difficult to specify in this International Standard what the exact relative humidity and temperature of
storage should be, since they depend upon the value of the film, the past storage history, the length of time
the film is to be kept, the size of the vault, the cost of various options and the climate conditions where the
facility is to be located. The cost/protection ratio has to be determined by the individual facility. Another very
important factor is the exact mix of the photographic objects in the collection, i.e. whether photographic prints
and plates are included and whether the materials are new or old.
Low relative humidities can cause excessive strain on the emulsion and result in high curl. Low humidities can
also cause serious problems with older historic records (see Annex G). The environmental conditions chosen
should fall within the guidelines of Table 1.
The recommended humidity and temperature conditions can be maintained either within individual storage
housings or within storage rooms containing such housings. When the regulation of the macroenvironment is
not possible, the microenvironment shall be controlled by means such as molecular sieves or silica gel, or by
conditioning to a lower humidity (see Annex G).
Very low humidity conditions may produce brittleness or curl in films having a gelatine emulsion, by extraction
of moisture from the emulsion. In such cases, it is good practice to recondition the film to a higher humidity
prior to use.
7.1.3.3 Recommended environment for colour films
The storage temperature for colour films shall be 2 °C or below for chromogenic materials (see
References [11][12]) and 21 °C or below for silver dye bleach materials. This can be provided by a storage
room controlled at the desired temperature and at the recommended relative humidity. Several relative
humidity/temperature combinations can be used as specified in Table 1.
As an alternative method, use the procedure described in the third paragraph of 7.1.3.2.
The user should balance the capital and operating cost of cold storage vaults or deep-freeze units with the
labour and material cost of bagging film.
7.1.3.4 Moisture-conditioning time
Moisture equilibration requires considerably more time than temperature equilibration. The time needed for
films to reach moisture equilibrium with a given atmosphere depends on the following main factors:
⎯ the film format (sheets, rolls);
⎯ the packing density and volume of sheet-film stacks or the number of convolutions of film rolls;
⎯ the moisture permeability of enclosure materials or containers, or both;
⎯ the difference between the initial and the desired final moisture content of the films;
⎯ the temperature at which the moisture conditioning occurs.
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A combination of these factors can prolong conditioning periods and may compromise the effectiveness of
low-temperature storage vaults, if the conditioning is expected to take place in storage. For example, a 150-
sheet stack will condition in less than two weeks at room temperature but will require six months at sub-zero
temperature (see Reference [13]).
For these reasons, preconditioning of films may be necessary before they are placed in their controlled
storage place. This can be accomplished with sheet films by exposing them to freely circulating air (see 7.3 for
air purity) of suitable temperature and relative humidity for 24 h. Longer periods will be needed if the sheets
are in stacks. Moisture equilibration of roll films takes much longer. Here again, free access of air will shorten
the required conditioning period, and rolls in moisture-permeable enclosures will require less time than those
in closed metal containers. However, even the latter will come to moisture equilibrium within several months at
room temperature (see References [12][13]). Film rolls that contain more than the desired quantity of moisture
can be dried by keeping them for two to three weeks in taped metal containers that contain suitable amounts
of silica gel or a molecular sieve.
If the relative humidity of the use environment is chosen to match that of the storage environment, moisture-
conditioning procedures can be reduced or eliminated. Matching the relative humidity levels between use and
storage has the added advantage of reducing physical stress on the film caused by relative humidity cycling
between storage and use. Unmatched humidity levels will have a strong influence on the time required to
reach moisture equilibrium.
7.1.3.5 Warm-up time
Films stored at temperatures significantly below room temperature will require some warm-up time before they
can be used, in order to prevent absorption or condensation of moisture on cold film surfaces. This warm-up
procedure requires that an adequate vapour barrier be wrapped around the film contents during the warm-up
period. Adequate time shall be provided to allow the total volume of film to approach room temperature (see
Annex F). The required warm-up time can vary between 1 h and 1 day, depending on the package size,
degree of insulation and temperature differential.
7.2 Air-conditioning requirements
Properly controlled air-conditioning may be necessary for maintaining humidity and temperature within the
limits specified, particularly for extended-term storage where the requirements are more stringent than for
medium-term storage. Slightly positive air pressure shall be maintained within the storage room or vault. Air-
conditioning installations and automatic fire-control dampers in ducts carrying air to or from the storage vault
shall be constructed and maintained on the basis of the recommendations contained in appropriate national
standards and regulations (e.g. see References [14][15]). They shall also conform to recommendations for
fire-resistive file rooms contained in appropriate national standards and regulations (e.g. see
References [16][17]). Masonry or concrete walls may release ste
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