ISO 18901:2010

INTERNATIONAL ISO
STANDARD 18901
Second edition
2010-05-01

Imaging materials — Processed silver-
gelatin-type black-and-white films —
Specifications for stability
Matériaux pour l'image — Films noir et blanc de type gélatino-
argentique traités — Spécifications relatives à la stabilité




Reference number
ISO 18901:2010(E)
©
ISO 2010

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ISO 18901:2010(E)
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ISO 18901:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .2
4 Film base requirements .3
5 Processed film requirements .3
5.1 Storage conditions .3
5.2 Safety film.3
5.3 Amount of free acid.3
5.4 Tensile properties and loss in tensile properties .3
6 Requirements for the emulsion and backing layers of processed film.4
6.1 Layer adhesion .4
6.2 Emulsion flow .4
6.3 Blocking.4
6.4 Thiosulfate concentration.4
6.5 Residual silver compounds.5
7 Image-stability requirements .5
7.1 General .5
7.2 Radiographic films .5
7.3 Microfilms.6
7.4 Other films.6
8 Test methods .6
8.1 Identification of film base .6
8.2 Accelerated-ageing conditions .6
8.3 Determination of the amount of free acid .7
8.4 Tensile property test for processed film.8
8.5 Tape-stripping adhesion test .8
8.6 Humidity-cycling adhesion test .9
8.7 Emulsion-flow test.10
8.8 Blocking test .10
8.9 Residual silver compound test .11
8.10 Image-stability test .11
Annex A (informative) Washing and the effect of residual thiosulfate on the developed silver
image .13
Annex B (informative) Effect of residual silver compounds on the developed silver image.14
Annex C (informative) Accelerated image-stability test for radiographic films .15
Annex D (informative) Accelerated image-stability test for microfilms.17
Annex E (informative) Accelerated image-stability test for aerial films .19
Bibliography.21

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ISO 18901:2010(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 18901 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18901:2002), 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 18900 to 18999.

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ISO 18901:2010(E)
Introduction
Since 1930, great advances have been made in the use of photographic films for the preservation of records.
The preservation of film records by governments, banks, insurance companies, industry and other enterprises
has been stimulated by a recognition of the economies in storage space, organization, accessibility and ease
of reproduction that result from the use of film records.
During the early development period of the art of copying documents, 35 mm nitrate motion picture film was
sometimes used. This material is highly flammable and is not a safety film as specified in ISO 18906. Nitrate
film is not acceptable for any record film. The manufacture of nitrate film declined after World War II and was
discontinued in most countries in the 1950s.
From about 1908 to 1956, the only safety-type film bases in commercial use were cellulose acetate, cellulose
acetate propionate and cellulose acetate butyrate. The useful life of these cellulose-ester-type bases is
somewhat conjectural because of limited practical experience. However, the results of laboratory incubation
tests indicate a useful life of at least 50 to 100 years when cellulose-ester-base films are stored under
recommended conditions (see References [1], [2], [3] and [4]).
A second type of polymer safety film base was introduced commercially in 1956. This is a polyester-class
material whose chemical name is polyethylene terephthalate.
NOTE Another type of polyester base, known as polyethylene naphthalate, has been used for APS (Advanced Photo
System) type films since 1996.
Polyester base has several advantages over cellulose-ester base, including greater strength, stiffness, tear
resistance and dimensional stability, which are important in many photographic applications (see
References [5] and [6]). Accelerated ageing tests supplemented by 35 years of practical experience indicate a
potential useful life of 500 years.
This International Standard provides image-stability predictions for three classes of black-and-white films in
terms of LE (life expectancy) ratings. These three classes are radiographic films, microfilms and all other films.
Two or three LE ratings are given for each of these film classes depending on their residual thiosulfate
concentrations.
Studies on the stability of silver-gelatin-type films have investigated the effect of residual hypo on the image
permanence of radiographic films, microfilms and aerial films (see References [7], [8] and [9]). This work
suggested modifications to the residual hypo limits and a more quantitative image-stability test was included in
the first edition of this International Standard. Residual hypo limits and image-stability tests are now included
for all film categories.
This International Standard identifies certain hazards to permanence attributable to the chemical or physical
characteristics of processed film and provides methods for evaluating them. Some of these are inherent film
characteristics, some are related to the chemical processing procedure and some are influenced by both
factors. However, storage conditions can also have a pronounced influence on film permanence. The
essential requirements for longevity are proper storage temperature and humidity as well as protection from
the hazards of fire, water, fungus, and atmospheric pollutants. Proper storage conditions are specified in
ISO 18902 and ISO 18911.

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INTERNATIONAL STANDARD ISO 18901:2010(E)

Imaging materials — Processed silver-gelatin-type black-and-
white films — Specifications for stability
1 Scope
This International Standard establishes the specifications for photographic films intended for the storage of
records.
It is applicable specifically to films with a base of safety cellulose ester or polyester having silver-gelatin
emulsions, processed to produce a black-and-white silver image by negative or full-reversal processing. It
applies to film processed using a monobath that includes thiosulfate as the fixing agent, followed by a
conventional wash. It also is applicable to silver films given a stabilizing treatment by partial or full conversion
to silver sulfide, silver selenide or gold.
This International Standard is applicable to films having ultrasonic or dielectric (induction-heated) splices. It
does not cover films with splices made of adhesive tape or solvent-type spIices.
NOTE Solvent-type splices are suspect since they sometimes retain traces of residual solvents containing peroxide,
which can pose some risk of oxidative attack on the silver image.
This International Standard is not applicable to films with chromogenic black-and-white images, colour images
of any type, or to films with a magnetic recording track. It does not apply to films with silver images produced
by dry or thermal processing or by diffusion-reversal processing, or to films that have been processed by a
monobath using means other than a thiosulfate-type fixing solution. It is not applicable to films where the silver
salts are removed by means other than thiosulfate solutions (see Reference [10]).
This International Standard is not applicable to films to which lacquers have been applied.
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 5-2, Photography and graphic technology — Density measurements — Part 2: Geometric conditions for
transmittance density
ISO 5-3, Photography and graphic technology — Density measurements — Part 3: Spectral conditions
ISO 527-3, Plastics — Determination of tensile properties — Part 3: Test conditions for films and sheets
ISO 18902, Imaging materials — Processed imaging materials — Albums, framing and storage materials
ISO 18906, Imaging materials — Photographic films — Specifications for safety film
ISO 18911, Imaging materials — Processed safety photographic films — Storage practices
ISO 18917, Photography — Determination of residual thiosulfate and other related chemicals in processed
photographic materials — Methods using iodine-amylose, methylene blue and silver sulfide
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ISO 18901:2010(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
emulsion layer
image or image-recording layer of silver-gelatin-type black-and-white films
NOTE There can be one or several emulsion layers.
3.2
extended-term storage conditions
storage conditions suitable for the preservation of recorded information having permanent value
NOTE The term “medium-term storage conditions” defines storage conditions suitable for the preservation of
recorded information for a minimum of 10 years.
3.3
film base
plastic support for the emulsion and backing layers
3.3.1
cellulose-ester base
base for recording materials composed mainly of the cellulose esters of acetic, propionic, or butyric acids, or
mixtures thereof
3.3.2
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)
3.4
full-reversal processing
reversal photographic processing that consists of development, bleach, clear, re-exposing and second
development, followed by fixing and washing
3.5
life expectancy
LE
length of time that information is predicted to be acceptable in a system after dark storage at 21 °C and 50 %
relative humidity (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
LE designation
rating for the life expectancy (3.5) 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 of storage.
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ISO 18901:2010(E)
3.7
non-curl backing layer
layer, usually made of gelatin, applied to the side of the photographic film base opposite that of the emulsion
layer, for the purpose of preventing curl
NOTE 1 It is comparable to the emulsion layer in thickness and is not removed in processing.
NOTE 2 Antihalation or other layers removed in processing are excluded from this definition.
3.8
safety film
safety photographic film
film that meets the flammability specifications defined in ISO 18906
4 Film base requirements
The base used for record films, as specified in this International Standard, shall be of a safety polyester or a
cellulose-ester type and can be identified by the method described in 8.1.
Some films on a cellulose-ester-type base can have a maximum LE rating of 100. Some films on a polyester
base can have a maximum LE rating of 500.
NOTE These limitations are based on historical experiences as discussed in the Introduction.
5 Processed film requirements
5.1 Storage conditions
Films shall be stored under the conditions specified in ISO 18902 and ISO 18911.
5.2 Safety film
Film shall meet the requirements specified in ISO 18906.
5.3 Amount of free acid
The cellulose-ester base shall not have an amount of free acid greater than 0,1 ml of 0,1 mol/l sodium
hydroxide solution per gram of film. The amount of free acid shall be measured in accordance with 8.3.
NOTE The degradation of cellulose-ester base is autocatalytic and proceeds rapidly when the free acid is greater
than 0,5 ml of 0,1 mol/l sodium hydroxide solution.
The volume of 0,1 mol/l sodium hydroxide equivalent to the amount of free acid of the processed film shall not
increase by more than 0,5 ml/l over its original value after the accelerated ageing described in 8.2.
5.4 Tensile properties and loss in tensile properties
Film specimens shall be processed and dried under the conditions used for film records.
Processed films shall be tested for tensile properties as described in 8.4 and shall have a tensile stress and
elongation at break as specified in Table 1 (unheated film). The loss in tensile properties after the accelerated
ageing test described in 8.2 shall not exceed the percentage specified in Table 1 (heated film).
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ISO 18901:2010(E)
Table 1 — Limits for tensile properties and loss in tensile properties on ageing
Film type Tensile stress at break Elongation at break
a
Cellulose-ester base 80 MPa 15 %
Unheated film: minimum
permissible tensile properties
Polyester base 140 MPa 75 %
Heated film: maximum permissible Cellulose-ester base 15 % 30 %
loss in tensile properties compared
Polyester base 15 % 30 %
with unheated film
a 6 2
1 MPa = 10 N/m .

6 Requirements for the emulsion and backing layers of processed film
6.1 Layer adhesion
6.1.1 Tape-stripping adhesion
Processed film shall not show any removal of emulsion layer or backing layer when tested as described in 8.5.
6.1.2 Humidity-cycling adhesion
The emulsion layer or backing layer of processed film shall not show separation or cracking that can impair its
intended use when tested as described in 8.6.
6.2 Emulsion flow
Processed film shall not show any visual evidence of emulsion flow (caused by partial emulsion remelting) as
a result of the accelerated ageing of the processed film. Emulsion flow shall be determined as described in 8.7,
when the accelerated ageing is performed as described in 8.2.
6.3 Blocking
Processed film shall show no evidence of blocking (sticking), delamination or surface damage when tested as
described in 8.8. A slight sticking of the film specimens that does not result in physical damage or a change in
the gloss of the surface shall be acceptable.
6.4 Thiosulfate concentration
Films shall be fixed in solutions containing either sodium thiosulfate (hypo) or ammonium thiosulfate (see
Reference [10]). Hypo-eliminating agents containing oxidizing agents such as peroxides or hypochlorites shall
not be used.
NOTE 1 Hypo-eliminating agents contain chemicals, usually strong oxidizing agents, that decompose thiosulfate (see
Annex B). These are distinguished from hypo-clearing baths, which are high ionic strength salt solutions. These facilitate
the washing of thiosulfate from the film, but do not chemically alter the thiosulfate.
After processing, the concentration of thiosulfite in the film shall be determined by one of the test methods
described in ISO 18917. The film shall not contain a greater concentration of residual thiosulfate, calculated as
2−
thiosulfate ions (S O ), than that specified in Table 2.
2 3
NOTE 2 Three methods for measuring residual-thiosulfate-based chemicals in film are described in ISO 18917. All
2
three methods are considered to be sufficiently reliable to report thiosulfate concentrations at the level of 0,014 g/m of
2− 2
S O . The methylene blue method is considered to be reliable for thiosulfate concentrations of 0,007 g/m . The
2 3
methylene blue and iodine amylose methods measure thiosulfate ions only. They are run within two weeks of processing.
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ISO 18901:2010(E)
The silver sulfide densitometric test method measures polythionate decomposition products and other residual chemicals
in addition to thiosulfate. The method can be run more than two weeks after processing. To determine thiosulfate levels
accurately with this method, a calibration curve for the particular film is necessary.
The analysis for thiosulfate shall be made on a film specimen from a clear area and shall be made within two
weeks after processing (see Annex B). The test method does not measure any change in the specimen
between the time of processing and the time of analysis, but is used to judge the state of the film after the test
has been carried out.
6.5 Residual silver compounds
Processed film shall not show more than an increase of 0,02 in Status A blue density when tested in
accordance with 8.9 (see Annex C).
Table 2 — Limits for thiosulfate concentration
Maximum permissible
Film classification
b
concentration of thiosulfate
Film type
(LE designation)
2c
g/m
LE-10 0,100
Radiographic films LE-100 0,050
a
LE-500 0,020
LE-100 0,030
Microfilms
a
LE-500 0,014
LE-10 0,100
Other films LE-100 0,050
a
LE-500 0,014
a
LE-500 film only applies to polyester-base film.
b
Values are for each side of the film that has a photographic layer or a non-curl backing layer.
Very low concentrations of thiosulfate due to excessive washing may cause the silver image to be more susceptible to
oxidative attack. These concentrations may be below the detection limits of ISO 18917.
c 2 2
0,010 g/m = 1 µg/cm .

7 Image-stability requirements
7.1 General
The specifications and test methods for image stability vary for different product types.
Visual diffuse density in accordance with ISO 5 or Status A blue density shall be measured on a densitometer
which has geometric conformance to ISO 5-2 and spectral conformance to ISO 5-3. Processed film
specimens shall be incubated as described in 8.10.3.
7.2 Radiographic films
An area of unexposed processed film shall be tested. The Status A blue density change of the unexposed
area shall be no greater than 0,05 density units after incubation. This requirement shall apply to LE-10,
LE-100 and LE-500 films.
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ISO 18901:2010(E)
7.3 Microfilms
An area of minimum density and another area having a visual diffuse density of 1,2 ± 0,1 on the processed
film specimen shall be tested.
Neither the minimum-density area nor the high-density area shall change by more than ± 0,1 visual diffuse
density units after incubation.
7.4 Other films
A minimum-density area and a 1,0 ± 0,1 Status A blue density patch of processed film shall be tested. Neither
the minimum-density area nor the high-density patch shall change by more than ± 0,1 Status A blue density
units after incubation. This requirement shall apply to LE-10, LE-100 and LE-500 films.
8 Test methods
8.1 Identification of film base
Remove all emulsion and backing layers from a specimen of unknown film, either by scraping or by the use of
enzyme solution. Then remove all sublayers by scraping.
Prepare a specimen of the base material by scuffing the surface with a suitable tool, such as a razor blade.
The general procedure is to move the scuffing device back and forth over the specimen manually while
exerting a very slight pressure. This removes the top layer of the base as a very fine dust. Carefully brush this
into a mortar.
Mix the specimen with about 100 times its mass of potassium bromide, previously ground to about 75 µm.
Prepare a strip or pellet as described in Reference [11].
Obtain an infrared (IR) absorption curve from the prepared pellet by means of an infrared-absorption
spectrometer. By comparing the IR absorption curve for the unknown with curves for known polymers, the
identity of the unknown can be established (see Reference [12]).
NOTE It is difficult, although not impossible, to distinguish between cellulose acetate, cellulose acetate propionate
and cellulose acetate butyrate bases using this method, but such separation is not necessary for the purposes of this
International Standard.
8.2 Accelerated-ageing conditions
Processed film shall be subjected to accelerated-ageing conditions to meet the requirements for an increase
in the amount of free acid, loss in tensile properties and emulsion flow.
Test specimens shall be conditioned at (23 ± 1) °C and (50 ± 2) % RH for at least 15 h. After conditioning,
place the specimens in a moisture-proof envelope and heat-seal the envelope. To prevent sticking between
adjacent specimens, it may be necessary to interleave them with polytetrafluoroethylene or uncoated
polyester. Ensure a high ratio of film-to-air volume by squeezing out excess air prior to heat-sealing. Use a
separate envelope for each film specimen. Double bagging is recommended to reduce any pinhole effect in
the envelopes. Heat the envelopes in an oven for 72 h at (100 ± 2) °C.
NOTE 1 A suitable moisture-proof envelope is a metal-foil bag that is coated on the inside with polyethylene for
heat-sealing.
NOTE 2 Incubation is accomplished in a closed environment to prevent escape of any acid that might be produced
during incubation. Such acid might catalyse further film-base degradation.
An alternative method of incubating the specimens in a closed environment is by placing them in 25 mm
borosilicate-glass tubes (see Reference [13]). Each tube shall have two flanged sections separated by a
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ISO 18901:2010(E)
gasket to provide a moisture seal and shall be held together by a metal clamp. Sufficient film specimens shall
be used to provide a high ratio of film-to-air volume.
NOTE 3 A suitable inert gasket can be made from polytetrafluoroethylene.
NOTE 4 In the text, specimens subjected to these accelerated-ageing conditions are designated “heated film”.
Comparison specimens kept at room
...