ISO 18947-2:2021

INTERNATIONAL ISO
STANDARD 18947-2
First edition
2021-10
Imaging materials and prints —
Abrasion resistance —
Part 2:
Rub testing of photographic prints
Matériaux pour l'image et les impressions — Résistance à
l'abrasion —
Partie 2: Essai de frottement des impressions photographiques
Reference number
ISO 18947-2:2021(E)
© ISO 2021

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ISO 18947-2:2021(E)
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© ISO 2021
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Published in Switzerland
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ISO 18947-2:2021(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General test background . 3
4.1 Summary of practice . 3
4.2 Significance and use . 3
4.3 Applicability and usage of alternative test methods . 3
5 Test device . 4
5.1 Test device description . 4
5.2 Test device preparation . 4
6 Samples . 4
6.1 Test target definition . 4
6.2 Preparation of samples and selection of the receptor material . 5
7 Test procedure .6
8 Evaluation . 6
8.1 General . 6
8.2 Instruments measurements . 6
8.3 Calculations . 7
8.4 Visual evaluation . 8
9 Test report . 8
Annex A (informative) Examples of test equipment, corresponding procedures and
operating parameters .10
Annex B (informative) Example of test target .13
Bibliography .14
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ISO 18947-2:2021(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.
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 documents 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).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions 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 first edition of ISO 18947-2:2021 cancels and replaces the first edition of ISO 18947:2013, which
has been technically revised.
The main changes are as follows:
— visual evaluation was added;
— details of the test procedure have been refined;
— drawings of the test devices have been updated.
A list of all parts in the ISO 18947 series can be found on the ISO website.
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.
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ISO 18947-2:2021(E)
Introduction
This method belongs to a series of test methods for the evaluation of permanence and durability of
image prints, which refers to the resistance of image prints to physical, mechanical, chemical and/
or environmental stresses in conditions of use. The permanence of the image under environmental
[10] [9]
stresses is tested by each stress factor individually: light (ISO 18937 ), heat (ISO 18936 ), ozone
[11] [12]
(ISO 18941 ), and humidity (ISO 18946 ). These stress factors are given by the ambient conditions,
over which the user often has limited control. The exposure to mechanical and physical stress may
often be controlled by the user, unless intense handling is integral to intended use. Tests for rubbing
of prints resulting in abrasion or smearing of the image are handled in the series ISO 18947, scratch
[7]
resistance is addressed in ISO 18922 (for film) and in the series ISO 18951 (all parts) (for reflection
prints, currently under development), respectively, and durability tests to simulate accidental exposure
[8]
to water or food spill is described ISO 18935 .
The process of rubbing a surface may result in different types of degradation, e.g. abrasion, scuffing,
smudging, and others. They may be observed as loss of colour intensity, scratches, changes in gloss,
coloration of former uncoloured areas, (coloured) material transfer to a receptor and others.
This document provides standardized requirements to evaluate and quantify the abrasion resistance of
image prints in their various formats such as hard copy prints and photo books.
Abrasion and smudge can include both accidental and repeating stresses, resulting from handling of the
image. The following are some examples of sources of abrasion:
— dirt particles rubbing on a printed surface;
— sheet-to-sheet abrasion (sliding motion of sheets relative to each other);
— prints sliding on tables or other flat surfaces;
— interaction with dirt or components inside of printers;
— magnets or other items used in the display of images.
This revised edition transforms ISO 18947 into a multipart standard to extend the applicability of
this standard to analogue and digital photographic, graphic and office prints. In addition, this revised
edition allows for the use of additional types of rub testers. The level of abrasion observed in a test
depends on the combination of many factors, including factors of the print material under test as well as
the test apparatus.
Different test devices show different levels of rub work, depending on load of the device, relative
movement of the samples (direction and speed), test length on the device and the selection of the
material and geometry of the abrading receptor.
Material factors that contribute to friction coefficients and therefore influence the susceptibility of
printed images to abrasive conditions include surface roughness, surface elasticity, substrate porosity
of samples and the chemical formulation, mobility as well as localization of the colorants on the surface
or within a receiver layer.
For photographic prints produced with photo-grade papers, a correlation between abrasion results on
linear, reciprocating abrasion testers was found in a Round Robin study of TC42/WG5, that included
imaging technologies like silver halide, inkjet, electro-photographic and dye diffuse thermal transfer.
[23][24][25]
Together with results from IPI this Round Robin study serves as background for this document,
which is dedicated to (quasi-)linear, reciprocating abrasion test of photographic prints on photo-grade
papers, including resin coated (RC photo-grade), barrier coated (water impermeable) paper and coated
[6]
(water permeable) paper as defined by ISO 18055-1 , as well as photo-grade films. The term (quasi-)
[13]
linear considers that the movement on the Sutherland type tester (see ISO 18947-1:2021 , A.2)
follows an arc segment of a circle with a large diameter, resulting in a mainly linear motion with a small
orthogonal component.
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INTERNATIONAL STANDARD ISO 18947-2:2021(E)
Imaging materials and prints — Abrasion resistance —
Part 2:
Rub testing of photographic prints
1 Scope
This document specifies tests to determine the abrasion resistance of photographic images for typical
use in indoor context that is characterized by mild abrasive conditions. Examples are flipping of pages
in an album, careful manual handling of prints (stacking, shifting) or use of magnets for attachment to
a board. Photographic images refer to individual prints or prints in albums, which can be produced by
a wide range of printing technologies, including silver halide, electrophotography, inkjet, dye diffusion
thermal transfer, commonly known as dye sublimation, and dye transfer processes. Photographic
images require “photo-grade” media, including coated or surface treated print materials, which
are prerequisite to obtain photographic quality with aforementioned printing technologies. Test
procedures are limited to (quasi-) linear, reciprocal abrasion test devices.
For other printing technologies (e.g. offset lithography and other photomechanical printing processes)
or non-photo-grade media or other levels of rubbing representative of other application profiles,
different test methods and/or device options may be considered (see ISO 18947-1).
Heavy duty abrasive conditions, such as floor tiles, floor graphics, abrasive cleaning and vehicle
graphics, are out of scope of this document.
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 2813, Paints and varnishes — Determination of gloss value at 20°, 60° and 85°
ISO 8254-1, Paper and board — Measurement of specular gloss — Part 1: 75 degree gloss with a converging
beam, TAPPI method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological 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
abrasion
loss of material from a surface or deformation of a surface, with changes in gloss, colour, or density, due
to frictional forces as a result of rubbing
Note 1 to entry: Surface deformations can result in changes in gloss and colour.
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ISO 18947-2:2021(E)
3.2
interval scale
scale established by a psychophysical method, which, in addition to possessing the
attributes of rank order (3.5), is distinguished by the fact that equal differences between numerical
values correspond to equal differences between properties measured (in sensory analysis, perceived
intensities)
Note 1 to entry: Larger values correspond to larger perceived intensities and the size of the difference between
two values reflects the size of the difference in perceived intensity of the property being measured. However, a
numerical value of zero may not indicate a total absence of the property and the ratio of two values cannot be
assumed to reflect the ratio of the perceived intensities.
3.3
minimum density
D
min
optical density corresponding to the maximum transmittance (film) or reflectance (paper) that a
photographic product can achieve
Note 1 to entry: The representation of the minimum density level of a photographic print depends on the printing
technology and includes (a) non-printed area of the print material, i.e. a substrate with or without a specific
image receiving or image forming layer, (b) coated or printed pre-white area (wherein a white layer is applied
before the image is printed such that a coloured or transparent substrate is covered) or (c) a printed area of the
material, where a transparent and/or white process colour (e.g. ink or toner) is printed image-wise.
Note 2 to entry: In this document, transparent substrates are evaluated in reflection mode by use of a white or
black backing, as suitable.
[SOURCE: ISO 12641-2:2019, 3.6]
3.4
quasi-linear
curvilinear motion with a small component of total displacement orthogonal to its
main direction of movement
Note 1 to entry: The Sutherland type abrasion tester provides an arc motion, where the length of the arc is much
shorter than the radius of the circle, resulting in a mainly linear motion with a small orthogonal component.
3.5
rank order
result of a method involving the arrangement by an observer of a series of stimuli in
order of increasing or decreasing image quality or an attribute thereof, in accordance with the set of
instructions provided
3.6
ratio scale
scale established by a psychophysical method, which has the properties of an interval
scale (3.2) but for which, in addition, the ratio between the values allocated to the two stimuli is equal
to the ratio between the perceived intensities of these stimuli
Note 1 to entry: With this scale, a numerical value of zero designates total absence of the property.
Note 2 to entry: The ratio scale is the only case for which it is meaningful to say that one result is, for instance,
ten times as great as another.
3.7
receptor
substrate used to rub the test specimen and onto which ink or other material that
is removed from the specimen is transferred
Note 1 to entry: An example of a receptor is the back side of the printed media (printed or D area) being
min
evaluated or a standard reference paper.
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ISO 18947-2:2021(E)
3.8
scuff
form of abrasion, leading to a change in gloss
3.9
smudge
result of rubbing leading to the displacement and re-deposition of materials into adjacent areas
Note 1 to entry: see abrasion (3.1).
4 General test background
4.1 Summary of practice
This method utilizes a (quasi-)linear, reciprocating rubbing device, or its equivalent, as e.g. described
in A.1 or A.2. The test specimen is placed in contact with a receptor surface under a specified load and
is rubbed with a back and forth motion at a specified frequency and for a specified number of cycles. A
cycle consists of two strokes, namely a forth stroke and a back stroke.
NOTE 1 Devices described in ISO 18947-1:2021, A.3 to A.6 were not included in the corresponding inter
laboratory test on photographic prints, and therefore it is not known, whether results from those abrasion tests
would also provide some level of correlation for selected test parameters.
After treatment, the test specimen is removed from the test device and evaluated for its degree of
degradation by measuring the change in gloss, optical density, colour and/or change in physical
appearance in both imaged (or printed) and minimum density, D , areas.
min
The receptor is analysed for the amount of colorant or coating transferred from the specimen as
evidenced by an increase in optical density or change in colour. Results are compared to equivalent,
non-abraded specimen and receptor, respectively.
NOTE 2 It is not the purpose of this document to define limits of acceptability or failure.
4.2 Significance and use
Depending upon their intended use applications, abrasion resistance is a desirable and sometimes
critical property of imaging materials. The result of abrasion can be degradation in both image quality
and appearance, and/or functionality. The amount of abrasion damage to a printed image is dependent
on many variables, including the nature of the abrading material, pressure, temperature, and humidity.
This method can be used to evaluate the relative abrasion, smudge, and scuff resistance of printed
photographic images and unprinted photographic materials under laboratory conditions for simulation
of the application profile of photographic images for intended use under “mild” abrasive conditions in
typical indoor context, including - but not limited to:
— handling of individual prints (rubbing during stacking, e.g. hand, shoebox, envelope, as well as
sliding with fingers);
— photographic images in albums (insertion in corner pieces, page-to-page rubbing);
— photobooks (page-to-page rubbing).
This method provides a reasonably simple procedure that can be used to set specifications for printed
photographic materials and determine whether a product meets a predetermined standard for
abrasion, smudge, or scuff resistance in aforementioned use.
4.3 Applicability and usage of alternative test methods
For more severe rubbing conditions, alternative test conditions may be more representative of
application profile envisaged (see ISO 18947-1).
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ISO 18947-2:2021(E)
5 Test device
5.1 Test device description
Test devices suitable for this test are (quasi-)linear, reciprocating abrasion testers as for example
shown in A.1 or A.2. Equipment that applies a similar reciprocating abrasive force in a similar manner
1)
as described in the preceding standards may also be used .
5.2 Test device preparation
The test device shall be set on a stable laboratory bench, in a room conditioned to the desired test
temperature and relative humidity. Conditions of (23 ± 3) °C and (50 ± 10) % relative humidity shall be
used for testing, unless specific product end-use requires different conditions.
6 Samples
6.1 Test target definition
Test targets consisting of uniform patches sized to fit the abrasion test device shall be used.
The target shall comprise a specified print substrate, with an associated colour as measured in the
minimum density, D , patch as well as the colour(s) of the imaging material utilized by the printing
min
system under test.
Required colours for test include:
— the 100 % patches of the primary colours, typically cyan, magenta, and yellow, which are addressed
by sRGB values (255, 255, 0), (255, 0, 255) and (0, 255, 255), respectively.
— neutral patches (composite black) with sRGB values (0, 0, 0) and secondary colours, typically red,
green and blue, addressed by sRGB values (0, 0, 255), (0, 255, 0) and (255, 0, 0), respectively.
Optionally, the following test patches may be tested in addition:
— the D patch as controlled by the sRGB values (255, 255, 255) – see also Note 1 to entry to term 3.3.
min
— 100 % patches of any system spots colours, e.g. orange and/or white ink.
— If the printing system makes use of multiple ink levels for a colorant (e.g. cyan and light cyan ink),
then a second set of patches of D may also be included. Further, a third set of patches falling
max
between 0,3 and 0,5 optical densities may also be included.
For monochrome imaging systems (e.g. silver halide, true monochrome inks) the requirements for the
test target design collapse into one colour patch, with D patch and intermediate density patches as
min
an optional test.
Each test patch shall be bordered by an adjacent minimum density, D , area, oriented with the
min
abrasive action of the test instrument, such that the smudging of colorant or imaging media into
adjacent minimum density area, D , can be assessed. Testing of the D area alone focusses on the
min min
abrasive effects of rubbing of the minimum area in the absence of colorant smearing. This may be of
1) Sutherland® Rub Tester (Danilee Co.), AB-301 Color Fastness Rubbing Tester (Tester Sangyo Co., Ltd.), FR-2
(Suga Test Instruments Co., Ltd.), and TRIBOGEAR TYPE 32 (Shinto Scientific Co., Ltd.) are examples of a suitable
products available commercially. This information is given for the convenience of users of this document and does
not constitute an endorsement by ISO of these products.
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ISO 18947-2:2021(E)
interest in view of the various constructions of the minimum density area as indicated by the Note 1 to
term 3.3.
NOTE A test target consisting of a white line, checkerboard, or other high contrast pattern can better
characterize smudge. In addition, a crockmeter can be useful in characterizing ink transfer from one surface to
[9]
another, see e.g. ASTM F 1319 .
The size of the patches shall be large enough to accommodate the size of the device mountings and
weights.
See suitable example of a test target in Annex B.
6.2 Preparation of samples and selection of the receptor material
Samples for abrasion testing shall be printed with test targets defined in 6.1. Samples may also be
prints treated at either side (varnished, laminated, bonded, backed, etc.) as in final application.
Samples shall be of a size appropriate for the test device to be used.
The drying time between printing or processing and abrasion testing may influence the results. Printed
samples shall be dried or cured and conditioned to the level of intended use prior to rub testing. Shorter
times may be tested in addition to investigate susceptibility of the printed images to abrasion by
conditions of processing and early handling after printing.
Water-based inkjet-printed samples shall be left face-open under the standard environmental condition
at least 14 days prior to rub testing. A shorter conditioning time may be agreed upon when the purpose
of the test is to evaluate the abrasion resistance at a shorter time after printing. During drying, curing,
and conditioning, dust deposition on the surface to be tested shall be avoided.
The receptor material shall be chosen in view of the intended use: backside of the print substrate
(stacking), frontside of another print (pages in an album), a standard receptor material (general
purpose). The evaluation of rub on printed receptor surfaces may be difficult. Therefore, standard
(unprinted) receptor substrates (recommended for third party evaluation) or back sides of front side
printed substrates (to simulate rubbing resistance for real production runs) are recommended.
Samples shall be tested in two directions perpendicular to each other. If there is a proof for non-
directionality rub testing in one direction is sufficient.
NOTE Samples can show different properties depending on the test direction. This can be caused by e.g.
fibre orientation, texture or others and can cause differences in rub tests. Coated photo-grade print materials
tend to have limited directionality.
Both the test specimen and the receptor shall be a flat sample with no surface irregularities, such as
scoring or creases.
If testing multiple samples, it is important that each has comparable, if not, identical colorant coverage
and colorant density. If the purpose of the test is to compare the print technologies, select appropriate
substrates and minimize substrate differences whenever possible.
Care shall be taken to avoid contaminating the sample with fingerprints during handling, as this can
influence the test results.
Samples and receptors shall be conditioned at (23 ± 3) °C and (50 ± 10) % relative humidity for 24 h or
longer. A shorter conditioning time may be agreed upon when the purpose of the test is to evaluate the
abrasion resistance at a shorter time after printing.
If tests need to be performed under different climatic conditions, samples also shall be conditioned in
this climate and the conditions shall be recorded.
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ISO 18947-2:2021(E)
7 Test procedure
The test shall be conducted under environmental conditions of (23 ± 3) °C and at a relative humidity of
(50 ± 10) %. The test procedure for each of the test devices referenced in 4.1 and 5.1 is slightly different
based on the specific design and capabilities of each of the test devices as described in A.1 and A.2. The
following are the key parameters that need to be controlled and reported relative to the specific test
device being used:
— the size of the sample specimen and the dimensions of the printed colour patches;
— the positioning of the reciprocal movement across the border of imaged and minimum density area,
D , in order to assess smudge;
min
— the specific receptor material and the dimensions of the receptor;
— the weight or load applied to either the test specimen or receptor;
— the number of rubbing cycles or strokes (one cycle comprises of two strokes, i.e. one stroke in forth
direction and one stroke in back direction);
— th
...