ISO 18930-2011 pdf free.Imaging materials – Pictorial colour reflection prints一Methods for evaluating image stability under outdoor conditions.
5.1 Accelerated laboratory weathering tests
Controlled laboratory tests are often used to provide standardized data and to benchmark materials. Predicting outdoor image display life from controlled laboratory tests without correlation data for the material in question between the laboratory test and natural outdoor exposure is not recommended.
Since the ability of images on digital printing media to withstand colour changes is a function of temperature, humidity, air pollutants, light and diurnal changes of environmental parameters, it is important that print stability be assessed under the conditions appropriate to the end use application.
The laboratory procedure described in this test practice is intended to provide a means for predicting the behaviour under actual outdoor exposure. Test results are useful for specification acceptance between producer and user, for quality control, and for research and product developmentt201121).
5.2 Outdoor weathering tests
Real-time outdoor exposure is the most reliable method of assessing outdoor image stability, but the actual exposure of a sample depends on the season and the weather, However, it is not as fast as accelerated laboratory tests. The outdoor test procedure described in this International Standard is intended to provide image stability data for an ink/media combination in a selected outdoor location. Note that the image stability indicated in this test will vary with the weather from year to yeart221.
6 Apparatus
6.1 Accelerated laboratory weathering test equipment
The exposure equipment shall consist of a light source with simulated direct outdoor daylight with a spectral power distribution as defined in CIE 85:1989, Table 4, and the operating limits defined in Annex A. A recommended match for direct outdoor daylight that is equivalent to CIE 85:1989, Table 4, is a cooled, filtered xenon high-pressure arc lamp. A “daylight filter” that gives the best match to the spectral power distribution of CIE 85:1989, Table 4, should be used. Matching the solar spectral power distribution, especially in the UV region, is extremely important. Irradiance, reference black panel temperature (BPT or BST). chamber (ambient) air temperature, and relative humidity need to be regulated to allow test conditions in the range specified in Clause 12. The apparatus should allow cycling between dark and light phases as well as water spray cycles and dry phases. Annex A shows appropriate operating limits for the spectral power distribution of xenon arc accelerated weathering instruments.
6.2 Outdoor weathering tests
Real-time outdoor weathering may be conducted at test sites that have the ability to mount samples onto racks with fixed or variable angles of inclination. Most testing is performed with the samples facing south (for the northern hemisphere) at a 45° angle of inclination. Advantages of testing at 45° rather than 90° are that seasonal variations in radiant exposure are minimized(221, space requirements are minimized because neighbouring sample racks are less likely to shade each other, and the average annual radiant exposure can be as much as twice as large (e.g. approximately 1,6 to 1,7 times as large for South Florida or Arizona). In some cases where a product is utilized on a vertical surface, such as vehicle graphics, testing is conducted at an angle of inclination of 90° facing either north or south.
Seasonal differences, such as temperature and relative humidity, will occur when tests are run at different times of year. It is critical that the outdoor tests be run for multiples of a calendar year so that separate tests have a basis for comparison. The testing service should provide information on the total solar UV irradiance at 45° for the samples tested, as well as tabulation on a day-to-day basis of the temperature and relative humidity highs, lows, and means(71. Often, this is published as a newsletter that is routinely sent to customers of the testing service. It is also recommended that the testing service provide ozone level data as well, if possible. Several manufacturers of accelerated weathering equipment offer testing services and outdoor exposure facilities.
7 Interferences
It is recognized that the fade of images on digital printing media will vary significantly because of factors such as initial colour density, the area printed (solid versus half-tone), the substrate, the colorant type (dye versus pigment inks), the number of passes (in multipass printing modes), ink load, print resolution, and the receiver coating type and thickness, Consequently, test results shall be determined individually for each print.
The rate of colorant degradation with light is often strongly dependent on humidity and air pollutants. Separating the environmental factors will not be possible in a real environment. This has to be taken into consideration when extrapolating to other display conditions. Guidance on the interference of environmental factors other than light, their importance in image degradation, and references to methods for measurement can be found in Reference (23).
Some outdoor environments are characterized by strong temperature and humidity fluctuations between day and night or sunny and overcast conditions. In cold weather, the presence of the sunlight creates strong temperature differences, especially in dark colours, that can lead to cracking and mechanical distortions. When samples are set out in the weather, another component for consideration is environmental materials:
both polluting gases and materials left by fauna and flora. Information about the levels of common pollutants is available, e.g. on the web sites of local environmental offices, meteorological or climatological web sites, or from the testing services. Unless measurement of resistance to these environmental effects is desired, many of these materials can be removed from samples by request, thus assuring a more controlled test. Effects of polluting gases can be examined or eliminated based on the weathering site location. Other possible is available, e.g. on the web sites of local environmental offices, meteorological or climatological web sites, or from the testing services. Unless measurement of resistance to these environmental effects is desired, many of these materials can be removed from samples by request, thus assuring a more controlled test. Effects of polluting gases can be examined or eliminated based on the weathering site location. Other possible sources of degradation to consider are acid rain, salt corrosion from the sea, haze due to pollution or fires, and bird droppings For removal of unwanted environmental materials, a gentle water rinse is recommended, but without scrubbing that can mar or abrade the surface. The use of mild soap solutions is permitted for laminated samples and for other materials that will not be damaged by this exposure.
Accelerated image stability tests for predicting the behaviour of colour images under normal outdoor conditions can be complicated by reciprocity failure. When applied to digital printing media, reciprocity failure refers to the failure of many types of colour images to degrade equally when irradiated to the same total light exposure (intensity time) by both high-intensity light for a short period and low-intensity light for a long period. The magnitude of any reciprocity failure can also be influenced by the test temperature, the moisture content of the test specimen, and lightldark cycling rates. Also note that apparent reciprocity failures have been observed in some materials due to the presence of ozone or other pollutants in accelerated weathering test chambersl24l.ISO 18930 pdf download.