ISO 18916:2025

International
Standard
ISO 18916
Second edition
Imaging materials — Photographic
2025-03
activity test for enclosure materials
— Processed silver‐gelatin and dye‐
gelatin prints
Matériaux d'imagerie — Test d'activité photographique pour
matériaux d'encadrement — Tirages traités à la gélatine
argentique et à la gélatine teintée
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test conditions . 2
4.1 Principle .2
4.2 Apparatus and materials .3
4.3 Incubation .3
4.4 Measurement .3
5 Image interaction test . 4
5.1 Procedure .4
5.2 Calculation .5
5.3 Requirements .6
6 Stain test . 6
6.1 Procedure .6
6.2 Calculation .7
6.3 Requirements .7
7 Mottle test . 7
7.1 Procedure .7
7.2 Requirements .7
8 Specific procedures . . 7
8.1 General .7
8.2 Adhesives and marking substances .7
8.3 Adhesives with carriers and double-sided adhesives .8
9 Test report .10
Annex A (normative) Modifications for dye coupler reactivity and diazo images .12
Annex B (informative) Colloidal silver image interaction detector . 14
Annex C (informative) Description of mottling .15
Annex D (informative) Applicability of the PAT to non‐silver gelatin‐based photographic
materials . 17
Annex E (informative) Applicability of the PAT to short‐term applications such as display and
transport .18
Bibliography . 19

iii
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
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with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
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Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
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related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18916:2007), which has been technically
revised.
The main changes are as follows:
This revision resolves issues regarding the scope of ISO 18916:2007 and its applicability to photographic
images that are not comprised of silver and/or gelatin-based materials. This revision removes these types of
materials from the scope of the document. The following additional changes have been made:
— A new Annex D addresses and warns against the use of the test outside of its intended scope, e.g. as a
general screen for oxidants and reductants and applied to all collection types. This annex also addresses
th
the test’s applicability towards 19 century photographic processes and digital hard copy such as inkjet,
dye sublimation, and electrophotography.
— A new Annex E includes guidance on the interpretation of test results for short-term applications, such
as display and transport.
— Language addressing the use of the test for consumer vs. museum applications has been added to the
introduction.
— The standard no longer specifies an annual testing requirement. Instead, the standard recommends
testing by batch or lot, and requires materials be re-tested upon changes in formulation or supplier
change, or upon other changes in production of the product.
— Test modifications for chromogenic (dye coupler) and diazo images have been moved to a normative
annex, as these are optional additional test methods for specific types of photographic processes and are
not requirements of the test.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
The use of materials for the storage, display, and transport of photographic records having a long-term value
has necessitated the development of International Standards to specify important considerations in this
field. The important elements affecting the useful life of imaging materials are as follows:
a) humidity and temperature of the environment;
b) hazards of fire;
c) hazards of water;
d) light exposure;
e) fungal growth;
f) contact with certain chemicals in solid, liquid, or gaseous form;
g) physical damage;
h) chemical processing;
i) damage from pests;
j) enclosures and containers in contact (or in close proximity) with the imaging material.
International Standards have been published which specify the material requirements for silver-gelatin
type film (ISO 18901), diazo film (ISO 18905), and vesicular film (ISO 18912). Specifications for proper
processing are also included in these documents. ISO 18918, ISO 18911 and ISO 18920 specify the storage
conditions for photographic plates, films, and paper prints, respectively.
In addition to the storage conditions, the enclosure materials used are extremely important. Processed
photographic materials in archival collections require a high degree of individual packaging to protect them
from atmospheric influences, dust, and handling damage, and also to keep them from contaminating each
other. For this purpose, a wide variety of paper and plastic materials are commercially available, fabricated
into albums, boxes, sleeves, envelopes, folders, mat boards, and interleaving tissues. However, it is absolutely
essential that these storage enclosures not cause harm to the photographic image. For optimum stability,
it is necessary that storage enclosures and their components meet the requirements in ISO 18902, which
includes passing the criteria of the photographic activity test.
The photographic activity test described in this document is a predictive test of chemical interactions
between the storage enclosure and the photographic material. It can also be used to evaluate possible
photographic activity caused by components of enclosures such as adhesives and marking substances.
This document uses detectors comprised of silver and gelatin to assess photographic activity, and therefore
the test applies to silver-gelatin type film. Two modifications of this test method are provided in Annex A
and apply to chromogenic (dye coupler) and diazo photographic materials. This test does not apply to other
non-silver-gelatin or non-dye-gelatin systems. Many other historical prints, such as collodion, albumen, and
historic silver-halide systems, contain either silver materials within the image or gelatin as a binder material,
but not both. For these types of historical prints, the photographic activity test may be applicable, but best
judgement should be used when applying the results of this test method to a specific type of historical print.
It is assumed that both consumers and collecting institutions such as museums, archives, and libraries,
wish to preserve their photographs for extended periods of time. The photographic activity test applies to
storage, display, and transport materials for both consumer and museum use. Consumers may choose to
deviate from recommendations for a variety of reasons, such as aesthetics or price, but at least will have
been informed on the potential consequences of those deviations.

v
International Standard ISO 18916:2025(en)
Imaging materials — Photographic activity test for enclosure
materials — Processed silver‐gelatin and dye‐gelatin prints
1 Scope
This document specifies the test method for evaluating possible chemical interactions between enclosures
and photographic materials that are produced in a light sensitive silver halide and gelatin containing layer,
processed using wet chemistry and where the final image retains metallic silver, herein referred to as silver-
gelatin materials. Modified versions of the test method are applicable to chromogenic (dye coupler) and
diazo photographic materials (see Annex A).
This document is applicable to all general photographic enclosure materials used for storage, display, and
transport, such as paper, tissue, cardboard, mat board and plastics. It is also applicable to components of
photographic enclosure materials such as adhesives and marking substances, including inks, paints, labels,
and tape. This document applies to all storage, display, and transport materials used for silver-gelatin
photographs whether intended for short or long-term use (see Annex E).
This document does not apply to non-silver-gelatin imaging systems. It does not pertain to harmful physical
interactions such as blocking (sticking together), dye bleed, adhesive migration, or plasticizer exudation.
It does not pertain to important criteria of enclosures such as their inherent chemical stability, physical
integrity, and workmanship. Passing the photographic activity test (PAT) alone does not indicate that
a material is archival. Quality requirements for photo-safe storage enclosures and their components are
covered in ISO 18902, which includes passing the criteria of the PAT.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements 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 5-4, Photography and graphic technology — Density measurements — Part 4: Geometric conditions for
reflection density
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
silver‐halide print
photographic print made from material sensitised with silver halide emulsion and chemically processed to
produce an image
3.2
image interaction
measurable density change in the image interaction detector, for example after contact with photographically
active foreign matter
Note 1 to entry: See 4.2.1 for as description of the image interaction detector.
3.3
mottle
localized non-uniform and easily recognizable visual density variation in the image interaction (3.2) detector.
Note 1 to entry: Mottle is used in this document in a different context to that defined in ISO 18913. More detail on this
is given in Annex C.
3.4
stain
measurable density increase in the stain detector, for example after contact with photographically active
foreign matter
Note 1 to entry: See 4.2.2 for as description of the stain detector.
3.5
blocking
undesired adherence between sheets of printed material
Note 1 to entry: Blocking can occur under a variety of pressures, temperatures, and humidity conditions, while in
storage or in use.
Note 2 to entry: Blocking effects include delamination, paper splitting, tearing, gloss changes, physical image transfer,
permanent bonding to adjacent materials and prints, and edge deformation
4 Test conditions
4.1 Principle
The photographic activity test applies to processed silver-gelatin and colour (dye-gelatin) materials. It can
apply to many historic photographic processes, such as other metallic silver-containing materials, and a
modified version applies to chromogenic (dye coupler) and diazo images. For discussion of this standard’s
applicability to other imaging systems, such as albumen, dye-diffusion-transfer prints, inkjet, etc., see
Annex D. The test consists of incubating the enclosure material or its components against the surfaces of
[8]
two sensitive detectors. The photographic density of these detectors is measured both before and after
incubation and the density changes compared with those obtained when the detectors are incubated
against a filter paper control. Three criteria are used to evaluate an enclosure, i.e. its tendencies to cause
image interaction, stain, and mottle on the detectors. A material shall pass all three criteria in order to
pass the overall photographic activity test. Specific details for each property are given in Clauses 5 to 7.
The test conditions described in Clauses 4 to 7 pertain to paper and plastic enclosures. Modifications of the
photographic activity test for enclosure components are given in Clause 8.
For enclosure materials intended for use with processed silver-gelatin and colour (dye-gelatin) images, only
the PAT described in Clauses 4 to 7 is applicable. The dye coupler reactivity test, described in Annex A, is
optional as the results are valid only for the specific chromogenic print product being investigated. Different
chromogenic print products can have different staining sensitivities. For enclosure materials intended for use
with diazo images, only the modified PAT described in Annex A is applicable. Applicability of the PAT detectors
for use with non-silver-gelatin prints and for short-term applications are discussed in Annexes D and E.
If a particular brand of commercially made enclosure materials is found to be safe for long-term storage
purposes, there is no assurance that subsequent batches will contain the same ingredients of the same purity,
chemical inertness, concentrations, or sound and sturdy construction. For this reason, it is recommended
that materials are tested by batch or lot. Materials shall always be re-tested upon changes in formulation or
supplier change, or upon other changes in production of the product. The test report shall be applicable to

the particular batch or lot of material tested. For materials which are manufactured in a variety of colours,
such as papers and inks, each colour is evaluated and reported separately.
4.2 Apparatus and materials
4.2.1 Image interaction detector, consisting of unprocessed colloidal silver (i.e. Carey Lea silver) in
1)
gelatin on a polyester base .
4.2.2 Stain detector, consisting of a conventional non-resin-coated grade 2 or 3 black-and-white
photographic paper having a relatively thick emulsion layer, processed to minimum density (D ) according
min
to the manufacturer's instructions. A warm-tone paper base or multigrade paper shall not be used. The
paper shall be processed without development, using fix, wash, hypo-clearing agent and wash stages.
4.2.2.1 Fix solution, consisting of 240 g of sodium thiosulfate pentahydrate and 15 g of anhydrous sodium
sulfite added to 1 l of water at 50 °C.
4.2.2.2 Hypo‐clearing agent, consisting of 5 g of anhydrous sodium sulfite and 26 g of sodium hydrogen
sulfite per litre of water.
It is recommended that the final washing be for 0,5 h with good agitation. This will avoid uneven leaching of
brightener.
NOTE Longer wash times can cause physical distortion and leaching of fluorescent brighteners. The uniformity of
the fluorescent brightener can be checked by visual examination using a UV lamp.
4.3 Incubation
Subject sandwiches of the detectors and enclosure material to an accelerated ageing test of 70 °C ± 1 °C and
86 % RH ± 3 % RH for 15 days, for example by means of a suitable temperature- and humidity-controlled
chamber.
Moisture condensation on the specimen sandwiches, when directly (i) inserting them into the temperature-
and humidity-controlled chamber at the test conditions, or (ii) upon removal, can confound the results and
shall be avoided. To mitigate moisture condensation the climate chamber can be equilibrated to transition
conditions of 70 °C ± 1 °C and 50 % RH ±3 % RH ~1 h before and after the test,
a) inserting: after the samples have equilibrated to 50 % RH ±3 % RH the humidity shall then be brought
to 86 % RH ± 3 % RH to commence the test, and
b) upon removal: upon completion of the test, the humidity can be lowered to 50 % RH ±3 % RH and the
specimens are allowed to equilibrate for one hour before removing from the chamber.
In practice, these additional steps have not shown to contribute to blocking of the detectors and filter paper.
Pull the sandwiches apart immediately after they are removed from the humidity chamber. Failure to do so
may result in the adhering of adjacent layers and detectors.
4.4 Measurement
Measure the Status A blue diffuse density of the detector strips both before and after incubation at four
locations for each strip. Make the after-incubation measurements at approximately the same locations as the
before-incubation measurements. Measurements shall not be made at the edges of the strip. Measurements
1)  The sensitivity of the colloidal silver detector is dependent upon the silver grain size and the degree of hardness. To
ensure test sensitivity and reliability, the colloidal silver detector can be obtained from the Image Permanence Institute,
Rochester Institute of Technology, 70 Lomb Memorial Dr., Rochester, NY 14623-5604, USA, or equivalent. Processed stain
detector may also be purchased from the Image Permanence Institute. This information is given for the convenience of
users of this International Standard and does not constitute an endorsement by ISO of the product named. Equivalent
products may be used if they can be shown to lead to the same results.

of density using either a filter instrument, such as a densitometer using filters to achieve Status A density,
or spectral instrument, such as a spectrophotometer, shall conform to the spectral conditions of ISO 5-3. If
measurements are made using a spectral instrument, weighting factors given in ISO 5-3 to achieve Status A
density shall be used. Instruments shall conform to the geometric conditions of ISO 5-2 for transmittance
density and ISO 5-4 for reflection density. Determine the transmittance density on the colloidal silver image
interaction detector and reflection density on the photographic paper stain detector.
5 Image interaction test
5.1 Procedure
Make a stack of two image interaction test sandwiches of the enclosure material and the colloidal silver
image interaction detector. Construct a sandwich so that the emulsion side of each image interaction
detector strip faces a filter paper separator as shown in Figure 1. These two sandwiches shall consist of
two strips of the image interaction detector, two strips of the enclosure material, two strips of a filter paper
separator (see Note), and two pieces of glass. The glass shall be clean and shall be discarded if there are any
signs of corrosion, such as dulling, iridescence, staining, cracking, pitting, efflorescence, or weeping. Apply
a pressure of 500 Pa to the enc
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