ISO 18907:2000
(Main)Imaging materials — Photographic films and papers — Wedge test for brittleness
Imaging materials — Photographic films and papers — Wedge test for brittleness
Matériaux pour l'image — Films et papiers photographiques — Détermination de la méthode dite <<du coin>>
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 18907
First edition
2000-05-15
Imaging materials — Photographic films
and papers — Wedge test for brittleness
Matériaux pour l'image — Films et papiers photographiques — Essai par la
méthode dite «du coin»
Reference number
ISO 18907:2000(E)
©
ISO 2000
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ISO 18907:2000(E)
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ii © ISO 2000 – All rights reserved
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ISO 18907:2000(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative reference .1
3 Term and definition .1
4 Principle.1
5 Apparatus .1
6 Sampling.2
7 Conditioning and test conditions.4
8 Procedure .5
9 Test report .6
Annex A (informative) Numbering system for related International Standards.7
Bibliography.9
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ISO 18907:2000(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.
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.
International Standard ISO 18907 was prepared by Technical Committee ISO/TC 42, Photography.
This first edition cancels and replaces the second edition of ISO 6077:1993 of which it constitutes a minor revision.
This International Standard is one of a series of 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 (see annex A).
Annex A of this International Standard is for information only.
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ISO 18907:2000(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 18907:2000(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, however, specify a universal brittleness test for all types of stress
encountered for which special tests can be required to correctly rate the material for brittleness.
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 although the brittleness level can
be quite different after processing from that before processing.
2 Normative reference
The following normative document contains provisions which, through reference in this text, constitute provisions of
this International Standard. For a dated reference, subsequent amendments to, or revisions of, the publication do
not apply. However, parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent edition of the normative document indicated below. For an undated
reference, the latest edition of the normative document referred to applies. Members of ISO and IEC maintain
registers of currently valid International Standards.
ISO 483:1988, Plastics — Small enclosures for conditioning and testing using aqueous solutions to maintain
relative humidity at constant value.
3 Term and definition
For the purposes of this International Standard, the following term and definition applies.
3.1
brittleness
property of materials that causes them to break or crack when deformed by bending
4Principle
Measurement of the opening of a wedge at which a specimen loop fails when subjected to high strains.
5 Apparatus
5.1 Wedge tester for brittleness
The wedge tester for brittleness consists of two non-parallel metal plates or jaws, which form a wedge or V as
shown in Figures 1 and 2. A clamp is attached to one jaw at the narrow end of the wedge to hold one end of the
specimen. A scale is provided which gives the wedge separation between the two jaws at any point (see [1] in the
bibliography).
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ISO 18907:2000(E)
The dimensions for the wedge tester are standardized for both a narrow and a wide tester. The narrow wedge (see
o
Figure 1) has a wedge angle of 9 and a maximum wedge opening of 25 mm. It is generally satisfactory for most
films. For more brittle films and papers, a wide wedge (see Figure 2) is recommended. It has a wedge angle of
o
28 and a maximum wedge opening of
...
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