Without a doubt, attractive packaging sells, because we tend to buy products with our eyes. Packaging is a brand vehicle and strongly contributes to the value of a product. Therefore, the printing must withstand the impact of light and heat. In other words, the product moves faster before color shifts or color fading of packaging occurs.
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Atlas SUNTEST XLS+
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Suitable accelerated test methods enable manufacturers of consumer products or packaging to assess color stability under different conditions: open-air markets in southern regions, outdoor in moderate climates with lower levels of illumination, or inside stores.
ISO 12040 Xenon-arc Testing
ISO 12040 has been developed in the late 1990’s for testing printed packaging. It is a filtered xenon-arc test simulating sunlight behind window glass. The test applies rather moderate irradiance and temperature levels. How long a test needs to run is determined by fading of a Blue Wool (BW) reference material to a specific Grey Scale rating. Most often, testers will choose the BW no. 5 and expose it until it has faded to Grey Scale 3 under ISO 12040 conditions.
Test duration inside an Atlas SUNTEST (CPS+, XLS+, XXL+FD) takes approximately 35 hours resulting in radiant exposure of approximately ~5000 kJ/m2 at 300-400 nm. A printing company in Germany reported for their products that this test correlates to approximately 380 hours outdoor sunlight exposure. That is about 1 month, when we consider 12 hours sunlight per day.
Time Pressure Dilemma of FMCG OEM
Since publication of ISO 12040 it has been found that 35 hours are not as short as it seems, particularly under time pressure for new product development. For more than 20 years, Packaging and FMCG OEMs have been successfully using SUNTEST models CPS+ and XLS+ with ISO 12040 and intensified testing.
By intensifying both irradiance and test temperature even shorter test times between 12 and 24 hours were achieved. From laboratory studies, natural exposures, and field tests, these companies have established well-confirmed correlation with end-use exposure. The following is an overview of several reports related to such accelerated SUNTEST packaging testing:
• ... the testing is equal to approximately 1 month heavy sunny outdoor conditions.
• ... simulates approximately 25 days (~300 hours) exposure to outdoor sunlight.
• ... expected durability under outdoor solar radiation is approximately 380 hours.
• … testing is suitable for demanding packaging such as cosmetics.
• … samples fading faster may be used in situations with lower solar radiation (Northern EU) or are only suitable for sunny exposures when they have a relatively rapid turnover.
Conclusions
A test being approximately equivalent to one month of hot sunny summer days (rich on UV and visible light) is obviously suitable addressing the risk of premature color change. This covers both outdoor sunlight and less aggressive indoor illumination.
Especially, economic SUNTEST CPS+ and XLS+ benchtop models helped companies to successfully build their brands with fast and reliable color fastness testing.
SUNTEST models have proven to do a good job for packaging testing, even if they lack the advanced precision of rotating rack xenon instruments. They can test flat and 3D samples and are well-equipped for accelerated shelf-life testing with the unique Atlas StoreLight™.
By Dr. Oliver D Rahaeuser, Senior Product Manager at Atlas MTT
