ISO 18907:2013
(Main)Imaging materials — Photographic films and papers — Wedge test for brittleness
Imaging materials — Photographic films and papers — Wedge test for brittleness
ISO 18907:2013 specifies a method for determining and expressing quantitatively the brittleness of photographic film and papers. The method is applicable to films with or without a gelatin backing and to fibre-based or resin-coated (RC) photographic papers. It may also be applied to either raw or processed materials.
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INTERNATIONAL ISO
STANDARD 18907
Second edition
2013-02-01
Imaging materials — Photographic
films and papers — Wedge test for
brittleness
Matériaux pour l’image — Films et papiers photographiques —
Détermination de la méthode dite <>
Reference number
ISO 18907:2013(E)
©
ISO 2013
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ISO 18907:2013(E)
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© ISO 2013
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Published in Switzerland
ii © ISO 2013 – All rights reserved
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ISO 18907:2013(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 1
5.1 Wedge tester for brittleness . 1
5.2 Test chamber . 2
6 Sampling . 2
6.1 Preparation of specimens . 2
6.2 Selection of specimens . 2
6.3 Size of specimens . 2
7 Conditioning and test conditions . 4
7.1 Conditioning of specimens . 4
7.2 Test conditions . 5
8 Procedure. 5
9 Test report . 6
9.1 Test data . 6
9.2 Significance . 6
Bibliography . 7
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ISO 18907:2013(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 18907 was prepared by Technical Committee ISO/TC 42, Photography.
This second edition cancels and replaces the first edition (ISO 18907:2000), of which it constitutes a
minor revision with the following changes:
— Clause 2 has been updated;
— Annex A has been removed.
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ISO 18907:2013(E)
Introduction
In the case of photographic films and papers, brittleness is an undesirable property since satisfactory
performance in equipment or in handling requires sufficient flexibility (or lack of brittleness) to ensure
good tolerances to bending stresses under the atmospheric conditions likely to be encountered in practice.
Photographic films and papers are laminates of two or more different materials, usually a plastic or
paper support and firmly bonded gelatin layers that contain image forming and other substances. These
laminate structures must have sufficient flexibility to withstand the stresses imposed by bending and
flexing during use. However, under low relative humidity and low temperature conditions, the gelatin
layers and/or support tend to become brittle. This can cause the formation of cracks and/or breaks
when the laminate is stressed beyond its diminished capacity to withstand bending and flexing.
Different types of brittle failure occur when film and paper are subjected to stress in different ways. For
example, failure can consist of very fine cracks in the emulsion (without a break in the support) which
are objectionable when the photograph is viewed. Under different conditions or with different materials,
failure can consist of cracks in the support or a complete break of all components of the laminate.
Brittleness is not an absolute physical property. The apparent brittleness of photographic material is
very dependent upon the manner in which it is mechanically treated as well as the ambient conditions of
temperature and relative humidity. As a result, no one test for brittleness is capable of ranking a variety
of types of photographic material as they would behave under widely different practical conditions.
The wedge test for brittleness specified in this International Standard subjects the photographic material
to a high rate of strain in a simple folding action. It has been an accepted method of rating brittleness for
many years and has correlated with product behaviour under many practical applications. It is a widely
accepted method in the photographic industry. Other methods used have consisted of flex tests in which
the specimen is subjected to a repeated folding action until it breaks, or the bending over mandrels of
different diameters. There are a considerable number of flexibility tests available and standardization
is not possible at this time.
Brittleness is affected adversely by both reduced temperature and reduced relative humidity. Brittleness
at low relative humidity is encountered more frequently than brittleness at low temperature in most
applications. Moreover, a marked change in brittleness can occur with only a very small change in
relative humidity below a level of about 25 %. Consequently, brittleness tests are carried out only in an
atmosphere which is very accurately controlled with respect to both temperature and relative humidity.
Brittleness is also very dependent on the sample thickness, increasing with increasing thickness of either
support or emulsion. For this reason, the thickness of the layers must be considered when comparing the
behaviour of different materials. The thermal and moisture exposure history of the material between
manufacture and testing can also affect the brittleness even though the sample is reconditioned to a
standard temperature and humidity.
Gelatin is generally more brittle than the support, so that photographic products having a gelatin layer on
only one side are usually more brittle when bent with the gelatin side out (that is, gelatin under tension).
Brittleness can vary with the bend axis depending upon the orientation of the support. There is generally
no directional effect in the brittleness of the emulsion.
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INTERNATIONAL STANDARD ISO 18907:2013(E)
Imaging materials — Photographic films and papers —
Wedge test for brittleness
1 Scope
This International Standard specifies a method for determining and expressing quantitatively the brittleness
of photographic film and papers. It does not, how
...
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