ISO/TR 18945:2018

TECHNICAL ISO/TR
REPORT 18945
First edition
2018-10
Imaging materials — Pictorial colour
reflection prints — Comparison of
image degradation observed between
ISO 18930 accelerated weathering test
method and outdoor exposure
Matériaux pour l’image — Réflexion des impressions photographiques
en couleurs — Comparaison de la dégradation de l’image observée
entre la méthode d’essai de vieillissement accéléré de l’ISO 18930 et
l’exposition extérieure
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 General considerations for accelerated weathering tests . 2
5 Materials . 4
6 Test methods . 5
6.1 Outdoor exposure tests . 5
6.2 Laboratory accelerated weathering tests . 5
6.3 Data analysis and work-up . 5
7 Results and discussion . 6
7.1 Colour Fade Acceleration Factors . 6
7.2 Replicability of data . 7
7.3 Applicability to multiple digital printing technologies . 8
7.4 Effects of colour and patch darkness . 9
7.5 Analysis of colour shifts . 9
7.6 Two-year data analysis .10
7.7 Correlation coefficients and predictive correlations .11
7.8 Example — Degradation of Material H4 .12
7.9 Comparison of material degradation during outdoor and ISO 18930 accelerated
laboratory weathering tests (see Annex G) .14
7.9.1 General.14
7.9.2 Colour fade graphs .14
7.9.3 Comparison of ISO 18930 accelerated tests to nine outdoor exposure sites .15
7.9.4 Colour shift graphs .15
8 Conclusions and recommendations .15
Annex A (informative) Spectral power distribution for accelerated laboratory weathering tests .16
Annex B (informative) Photographs of weathered test target degradation .17
Annex C (informative) Comparison of accelerated weathering test methods and outdoor results .21
Annex D (informative) The various types of deterioration observed in ISO 18930 .28
Annex E (informative) Effects of the angle of inclination in outdoor testing.30
Annex F (informative) Environmental condition data under real outdoor conditions .38
Annex G (informative) Comparison of material degradation during outdoor and ISO 18930
accelerated laboratory weathering tests .42
Bibliography .93
Foreword
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iv © ISO 2018 – All rights reserved

Introduction
Printed digital images are used in many applications in which they are exposed to outdoor weathering.
ISO 18930 provides standardized test procedures to evaluate image stability both in real-time outdoor
weathering tests and in accelerated laboratory simulations of the weathering process. Accelerated
laboratory weathering tests have been developed as a result of the desire to obtain test results faster
than would be obtained by actual outdoor exposure. However, accelerated weathering tests only have
value if they can be correlated with actual outdoor performance.
TECHNICAL REPORT ISO/TR 18945:2018(E)
Imaging materials — Pictorial colour reflection prints —
Comparison of image degradation observed between ISO
18930 accelerated weathering test method and outdoor
exposure
1 Scope
This document describes the experimental framework, results, and conclusions from a round robin test
that was performed in order to establish correlations between accelerated weathering according to the
ISO 18930 test method and outdoor weathering at nine outdoor sites.
The types of digital printing technology that were used in this round robin test are aqueous inkjet,
solvent inkjet, UV curable inkjet, digitally-exposed silver halide, and thermal mass transfer. The
image print stability data and correlations of this document are to be considered illustrative of the
performance of these classes of materials. Extension of these correlations to other classes of materials,
such as dye sublimation, is verified by appropriate experimentation.
2 Normative references
There are no normative references in this document.
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 http: //www .electropedia .org/
3.1
digital printing media
recording elements used by digital printers to receive inks or pre-formed colourants
EXAMPLE The substrate may be paper, plastic, canvas, fabric, metal, or other ink-receptive material; the
substrate may, or may not, be coated with an ink-receptive layer. The category of digital printers includes inkjet,
electrophotographic, and thermal transfer.
3.2
laminate
overlaminate
layer of material that goes over the top or bottom of a specimen
Note 1 to entry: Usually to provide water-resistance, physical, and/or ultraviolet (UV) light protection of the
specimen during a weathering test. A layer of protective film is applied with a pressure-sensitive or heat-
activated adhesive.
3.3
accelerated laboratory weathering
simulated weathering where instruments (weathering devices) are used to obtain very controlled
conditions that simulate, to some degree, and generally accelerate, the outdoor weathering results
[2] [16]
Note 1 to entry: The use of such instruments is described in ISO 4892-1 and ASTM G151 .
3.4
outdoor weathering
actual placement of specimens outdoors in specific locations
Note 1 to entry: This is differentiated from simulated weathering where instruments (weathering devices) are
used to obtain very controlled conditions that simulate, to some degree, and generally accelerate the outdoor
[2] [16]
weathering results. Use of such instruments is described in ISO 4892-1 and ASTM G151 .
3.5
reciprocity failure
non-equivalence in weathering results between a long exposure/low-intensity experiment and its short
exposure/high-intensity counterpart with an equivalent intensity-time product
3.6
daylight filter
optical filter or combination of filters that modifies the spectral power distribution of a light source to
better represent some defined daylight spectrum
Note 1 to entry: These filters are not related to the blue filters used in the photographic industry for the change
of correlated colour temperature of light sources.
[5]
Note 2 to entry: Adapted from ISO 18913 .
3.7
coefficient of variation
standard deviation of a variable divided by the arithmetic mean of the variable
3.8
Pearson correlation coefficient
statistical measure of the degree of linear correlation between two variables, with value between −1,0
and +1,0 inclusive, where a value of +1,0 represents perfect positive correlation, a value of 0,0 signifies
no correlation, and a value of −1,0 represents perfect negative correlation
3.9
acceleration factor
ratio of the time required to reach an endpoint in an outdoor weathering test to the time required to
reach the same endpoint in a laboratory accelerated weathering test
3.10
colour fade acceleration factor
acceleration factor for which the bases of comparison are the ratios of reflected optical density during
the test to the initial reflected optical density prior to
...