SIST ISO 18903:2011

INTERNATIONAL ISO
STANDARD 18903
First edition
2002-07-01
Imaging materials — Films and paper —
Determination of dimensional change
Matériaux pour l'image — Films et papiers — Détermination des variations
dimensionnelles
Reference number
©
ISO 2002
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ii © ISO 2002 – All rights reserved

Contents Page
Foreword.v
Introduction.vi
1 Scope .1
2 Normative reference.1
3 Terms and definitions .1
4 Measurement technique.3
5 Sampling.3
5.1 Selection of specimens.3
5.2 Handling of specimens .3
5.3 Conditioning of specimens.3
5.4 Processing of specimens .4
6 Conditioning.4
6.1 Constant humidity chamber .4
6.2 Standard temperature and humidity.4
7 Test for humidity coefficient of expansion .5
7.1 Procedure .5
7.2 Calculations .5
7.3 Test report .5
8 Test for thermal coefficient of expansion .5
8.1 General.5
8.2 Procedure .6
8.3 Calculations .6
8.4 Test report .6
9 Test for dimensional change due to processing.7
9.1 General.7
9.2 Coding system .7
9.3 Procedure .7
9.4 Calculations .8
9.5 Test report .8
10 Test for dimensional change due to processing plus ageing.8
10.1 Ageing conditions .8
10.2 Ageing time .9
10.3 Procedure .9
10.4 Calculations .9
10.5 Test report .9
Annex A (informative) Numbering system for related International Standards .10
Annex B (informative) Methods of measuring dimensional change.12
Annex C (informative) Dimensional hysteresis in photographic materials.13
Bibliography .17

iv © ISO 2002 – All rights reserved

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 18903 was prepared by Technical Committee ISO/TC 42, Photography.
This first edition of ISO 18903 cancels and replaces ISO 6221:1996, which has been technically revised.
Annexes A to C of this International Standard are for information only.

Introduction
Photographic films and papers exhibit temporary or reversible dimensional changes as well as permanent
dimensional changes. This International Standard is designed to provide uniform methods for treating the
specimens and for expressing the dimensional changes which occur with changes in atmospheric conditions and
those which occur in processing and ageing.
Temporary or reversible dimensional changes are the result of changes in the equilibrium moisture content (which
is determined by the relative humidity of the surrounding atmosphere) or changes in temperature. Permanent
dimensional changes occur as the result of processing and ageing. The rate of permanent shrinkage of film
generally increases with temperature, but decreases with time. The rate of shrinkage may also be greatest at either
high or low relative humidity, depending on the type of film. Some materials, particularly photographic film on
polyester base, can show a swelling after a high humidity exposure.
The increasing use of photographic films in recent years, in applications where dimensional stability is critical, has
emphasized the importance of an accurate measure of dimensional properties. For example, in photomechanical
reproductions a dimensional change of as little as 0,01 % may be of practical importance. In the case of aerial
mapping, uniform shrinkage is not serious since it can be easily corrected by a change in magnification, but any
difference in shrinkage in the two principal directions is a source of error. Any localized or non-uniform changes in
dimension are of practical concern.
The dimensional change properties of any film or paper depend not only on their composition and method of
manufacture, but also on their thermal and moisture content history. Accurate evaluation of such properties
requires some control over the specimen history as well as very precise control over the conditioning and
measuring procedures. Film and paper dimensions are also subject to hysteresis effects. These are relatively more
important with the more stable materials such as polyester photographic base films.
Additional information on the dimensional characteristics of photographic films and papers and on methods of
measurement may be found in the bibliography.

vi © ISO 2002 – All rights reserved

INTERNATIONAL STANDARD ISO 18903:2002(E)

Imaging materials — Films and paper — Determination of
dimensional change
1 Scope
This International Standard specifies a method for determining the dimensional change of photographic films and
papers caused by:
 variations in equilibrium moisture content due to change in the relative humidity (RH) of the atmosphere
(humidity coefficient of expansion);
 change in temperature (thermal coefficient of expansion);
 processing;
 ageing.
This International Standard deals with the moisture content and thermal history of the specimens before
measurement, the atmospheric conditions during measurement, and the treatment of the data. It does not describe
the various experimental techniques used to make the measurements.
This International Standard is not suitable for determining the dimensional change of instant photographic film.
2 Normative reference
The following normative document contains 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 edition of the normative document 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/TR 18931:2001, Imaging materials — Recommendations for humidity measurement and control
3 Terms and definitions
For the purposes of this International Standard, the following terms and definitions apply.
3.1
conditioning
exposure of a specimen to air at a given relative humidity and temperature until equilibrium is reached
3.2
differential dimensional change
difference between the dimensional changes of the material in the two principal directions (length and width)
NOTE Polyester-based films frequently have maximum and minimum dimensional changes in directions other than the
length or width. These can be determined by rotating and viewing the uncoated base between a pair of crossed polarizers.
When the direction corresponding to either the maximum or minimum dimensional change is coincident with the optical axis of
one polarizer, there is minimum light transmission through the base.
3.3
dimensional change d
...