ISO 6077:1993

INTERNATIONAL
ISO
STANDARD
6077
Second edition
1993-02-01
Photography - Photographit films and
Papers - Wedge test for brittleness
Photographie - Films et Papiers photographiques - Determination de Ia
methode dite “du coin ”
Reference number
ISO 6077:1993(E)

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ISO 6077:1993(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. Esch 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.
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.
International Standard ISO 6077 was prepared by Technical Committee
ISOfTC 42, Photography.
This second edition cancels and replaces the first edition
(ISO 6077:1980), of which it constitutes a technical revision.
Annex A of this International Standard is for information only.
0 ISO 1993
All rights reserved. No part of this publication may be reproduced or utilized in any form or
by any means, electronie or mechanical, including photocopying and microfilm, without per-
mission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1 211 Geneve 20 l Switzerland
Printed in Switzerland
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ISO 6077:1993(E)
Introduction
Brittleness is a property of many materials under specific atmospheric
conditions, which Causes them to break or Crack when deformed by
bending. In the case of photographic films and Papers it is an undesirable
property since satisfactory Performance in equipment or in handling re-
quires sufficient flexibility (or lack of brittleness) to ensure good tolerantes
to bending Stresses under the atmospheric conditions likely to be en-
countered in practice.
Photographit 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 im-
posed 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 tan 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 tan 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 tan 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. lt has been an accepted
method of rating brittleness for many years and has correlated with prod-
uct behaviour under many practical applications. lt 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 ac-
tion until it breaks or the bending over mandrels of different diameters.
There are a considerable number of flexibility tests available and stan-
dardization is not possible at this time.
Brittleness is affected adversely by both reduced temperature and re-
duced 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 tan 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 ac-
curately controlled with respect to both temperature and relative humidity.
. . .
Ill

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ISO 6077:1993(E)
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 be-
haviour of different materials. The thermal and moisture exposure history
of the material between manufacture and testing tan also affect the
brittleness, even though the Sample is reconditioned to a Standard tem-
perature 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 tan 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 6077:1993(E)
Photography - Photographit films and Papers -
Wedge test for brittleness
1 Scope 3 Principle
Measurement of the opening of a wedge at which a
This International Standard specifies a method for
specimen loop fails when subjected to high strains.
determining and expressing quantitatively the brittle-
ness of photographic film and Papers. lt does not,
however, specify a universal brittleness test for all
4 Apparatus
types of stress encountered for which special tests
tan be required to correctly rate the material for
brittteness.
4.1 Wedge tester for brittleness
The method is applicable to films with or without a
The wedge tester for brittleness consists of two
gelatin backing and to fibre-based or resin-coated (RC)
non-parallel metal plates or jaws, which form a wedge
photographic Papers. lt may also be applied to either
or V as shown in figures 1 and 2. A clamp is attached
raw or processed materials although the brittleness
to one jaw at the narrow end of the wedge to hold
Ievel tan be quite different after processing from that
one end of the specimen. A scale is provided which
before processing.
gives the wedge Separation between the two jaws at
any Point. 111
The dimensions for the wedge tester are standardized
for both a narrow and a wide tester. The narrow
2 Normative reference
wedge (see figure 1) has a wedge angle of 9,O” and
a maximum wedge opening of 25 mm. It is generally
The following Standard contains provisions which,
satisfactory for most films. For more brittle films and
through reference in this text, constitute provisions
Papers, a wide wedge (see figure 2) is recommended.
of this International Standard. At the time of publi-
lt has a wedge angle of 28,O” and a maximum wedge
cation, the edition indicated was valid. All Standards
opening of 74 mm.
are subject to revision, and Parties to agreements
based on this International Standard are encouraged
to investigate the possibility of applying the most re-
4.2 Test chamber
cent edition of the Standard indicated below. Mem-
bers of IEC and ISO maintain registers of currently An air-conditioned box or waIk-in room shall be used
valid International Standards. for both conditioning and testing. The temperature
shall be controlled within + 1 “C and the relative hu-
ISO 483: 1988, Plastics - Small enclosures for con- midity to within + 1 %l) of the specified values. The
ditioning and testing using aqueous solutions to linear air velocity shall be at least 15 cm/s. If a walk-in
conditioned room is used, the air velocity shall be ad-
main tain relative humidity at constan t value.
equate to maintain the conditions specified. The
1) To control the relative humidity to this accuracy usually requires a dewpoint method.
1

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ISO 6077:1993(E)
number of Personne1 permitted in the room during reached. This may be determined by weighing speci-
testing shall be limited and precautions shall be taken mens at regular intervals and determining
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