ISO 18901:2002

Imaging materials — Processed silver-gelatin type black-and-white films — Specifications for stability

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 by a monobath, which 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 by means of adhesive tape or solvent-type spIices. NOTE Solvent-type splices are suspect since they may retain traces of residual solvents containing peroxide which can pose some risk of oxidative attach on the silver image. This International Standard is not applicable to films with chromogenic black-and-white images, colour images of any type, nor 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, nor to films that have been processed by a monobath using a 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. This International Standard is not applicable to films to which lacquers have been applied.

Matériaux pour l'image — Films noir et blanc de type gélatino-argentique traités — Spécifications relatives à la stabilité

General Information

• Status: Withdrawn
• Publication Date: 06-Mar-2002
• Withdrawal Date: 06-Mar-2002
• ICS: 37.040.20 - Photographic paper, films and plates. Cartridges
• Technical Committee: ISO/TC 42 - Photography
• Drafting Committee: ISO/TC 42/WG 5 - Physical properties and image permanence of photographic materials
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 12-Apr-2010

Relations

• Revised: ISO 18901:2010 - Imaging materials — Processed silver-gelatin-type black-and-white films — Specifications for stability
• Effective Date: 15-Apr-2008
• Revises: ISO 10602:1995 - Photography — Processed silver-gelatin type black-and-white film — Specifications for stability
• Effective Date: 15-Apr-2008

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 18901
First edition
2002-02-15


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




Reference number
ISO 18901:2002(E)
©
 ISO 2002

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ISO 18901:2002(E)
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ii © ISO 2002 – All rights reserved

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ISO 18901:2002(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 .6
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 .10
8.10 Image-stability test .11
Annex A (informative) Numbering system for related International Standards .12
Annex B (informative) Washing and the effect of residual thiosulfate on the developed silver image .14
Annex C (informative) Effect of residual silver compounds on the developed silver image .15
Annex D (informative) Accelerated image-stability test for radiographic films.16
Annex E (informative) Accelerated image-stability test for microfilms.18
Annex F (informative) Accelerated image-stability test for aerial films .20
Bibliography.22

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ISO 18901:2002(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.
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 International Standard 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 first edition cancels and replaces the second edition of ISO 10602, of which it constitutes a technical revision.
This International Standard is one of a series of International Standards dealing with the physical properties and
stability of imaging materials. To facilitiate identification of these International Standards, they are assigned a
number within the block from 18900 to 18999 (see annex A).
Annexes A to F of this International Standard are for information only.
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ISO 18901:2002(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 100 years when cellulose-ester base films are stored under recommended conditions (see [1],
[2], [3], [4] in the bibliography).
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. [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 [5], [6] in the bibliography). 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 [7], [8], [9] respectively in the bibliography). This
work suggested modifications to the residual hypo limits and a more quantitative image-stability test was included
in the first edition of ISO 10602. 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 gives methods of 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 also can 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 18901:2002(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 by a monobath, which 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 by means of adhesive tape or solvent-type spIices.
NOTE Solvent-type splices are suspect since they may 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, nor 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, nor to films that have been processed by a monobath
using a 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 [10] in the bibliography).
This International Standard is not applicable to films to which lacquers have been applied.
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 5-2:2001, Photography — Density measurements — Part 2: Geometric conditions for transmission density
ISO 5-3:1995, Photography — Density measurements — Part 3: Spectral conditions
ISO 527-3:1995, Plastics — Determination of tensile properties — Part 3: Test conditions for films and sheets
ISO 18902:2001, Imaging materials — Processed photographic films, plates and papers — Filing enclosures and
storage containers
ISO 18906:2000, Imaging materials — Photographic films — Specifications for safety film
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ISO 18901:2002(E)
ISO 18911:2000, Imaging materials — Processed safety photographic films — Storage practices
ISO 18917:1999, Photography — Determination of residual thiosulfate and other related chemicals in processed
photographic materials — Methods using iodine-amylose, methylene blue and silver sulfide
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 for ever, 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
emulsion layer(s)
image or image-forming layer(s) of photographic films, papers and plates
3.3
extended-term storage conditions
storage conditions suitable for the preservation of recorded information having permanent value
3.4
film base
plastic support for the emulsion and backing layers
3.4.1
cellulose-ester base
base for record materials composed mainly of the cellulose esters of acetic, propionic, or butyric acids, or mixtures
thereof
3.4.2
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)
3.5
full-reversal processing
reversal photographic processing that consists of development, bleach, clear, reexposing and second
development, followed by fixing and washing
3.6
life expectancy
LE
length of time that information is predicted to be acceptable in a system after dark storage at 21 °C and 50 % RH
3.7
LE designation
rating for the “life expectancy” of recording materials and associated retrieval systems
NOTE The number following the LE symbol is a prediction of the minimum life expectancy in years for 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 18901:2002(E)
3.8
medium-term storage conditions
storage conditions suitable for the preservation of recorded information for a minimum of 10 years
3.9
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.
3.10
safety photographic film
photographic film which passes the ignition-time test and the burning-time test 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 the equivalent of 0,1 ml of 0,1 mol/l
sodium hydroxide solution per gram of film. The amount of free acidity 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.
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 accelerated ageing
as described in 8.2 shall not exceed the percentage specified in Table 1 (heated film).
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ISO 18901:2002(E)
Table 1 — Limits for tensile properties and loss in tensile properties on ageing
Film type Tensile stress at break Elongation at break
Unheated film

Minimum permissible tensile properties:
a
Cellulose-ester base  80 MPa 15 %
Polyester base 140 MPa 75 %
Heated film
Maximum permissible loss in tensile properties

compared with unheated film:
Cellulose-ester base 15 % 30 %
Polyester base 15 % 30 %
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 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 [10] in the
bibliography). Hypo-eliminating agents containing oxidizing agents such as peroxides or hypochlorites shall not be
used.
NOTE Hypo-eliminating agents contain chemicals, usually strong oxidizing agents, which decompose thiosulfate (see
annex B). These are to be 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.
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ISO 18901:2002(E)
After processing, the film shall not contain a greater concentration of residual thiosulfate calculated as thiosulfate
2−
ions (S O ) than that specified in Table 2 when determined by one of the test methods described in ISO 18917.
2 3
NOTE Three methods for measuring residual thiosulfate-based chemicals in film are described in ISO 18917. All three
2 2−
methods are considered to be sufficiently reliable to report thiosulfate concentrations at the level of 0,014 g/m of S O . The
2 3
2
methylene blue method is considered to be reliable for thiosulfate concentrations of 0,007 g/m . The methylene blue and iodine
amylose methods measure thiosulfate ions only. They are to be run within two weeks of processing. The silver sulfide
densitometric test method measures polythionate decomposition products and other residual chemicals in addition to thiosulfate.
The method may 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 keeping of the film following the time of the
test.
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 concentration
b, c, d, e
a of thiosulfate
Film type Film classification
2
g/m
Radiographic films LE-10 0,100
LE-100 0,050
LE-500 0,020
Microfilms LE-100 0,030
LE-500 0,014
Other films LE-10 0,100
LE-100 0,050
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.
c
The concentration of thiosulfate is expressed in grams per square metre, which conforms to SI units.
d
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.
e 2 2
0,010 g/m = 1µg/cm

7 Image stability requirements
7.1 General
The specifications and test methods for image stability vary for different product types.
ISO visual diffuse density 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.
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ISO 18901:2002(E)
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.
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 [11] in the bibliography.
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 [12] in the bibliography).
NOTE It is difficult, although not impossible, to distinguish between cellulose acetate, cellulose-acetate propionate and
cellulose-acetate butyrate bases by this method, but such separation is not necessary for the purpose 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 effect of pinholes 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.
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ISO 18901:2002(E)
NOTE 2 Incubation is accomplished in a closed environment to prevent escape of any acid that may be produced during
...