Scope 1. This practice is intended to reproduce the weathering effects that occur when materials are exposed to sunlight either direct or through window glass and moisture as rain or dew in actual usage. This practice is limited to the procedures for obtaining, measuring, and controlling conditions of exposure. Note 1: Practice G describes general procedures to be used when exposing nonmetallic materials in accelerated test devices that use laboratory light sources. Note 2: A number of exposure procedures are listed in an appendix; however, this practice does not specify the exposure conditions best suited for the material to be tested. Different types of fluorescent UV lamp sources are described.
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When rays of sunlight—particularly UV rays—bombard a surface, they degrade smaller pigment particles, changing the surface color and creating a chalky effect. Cracking, peeling, de-glossing, oxidation, and tensile weakening are additional outcomes of exposure; sometimes such deterioration can even occur through window glass. Moisture takes its own toll on surfaces, and the combination of sunlight and moisture can amplify damage, costing millions of dollars of depreciation each year.
The ASTM G and G tests empower manufacturers to design products that can withstand exposure to sunlight and moisture. Ultimately, the most realistic way to test for weathering is to allow the product to degrade in real time, with outdoor testing panels.
In the U. Due to time constraints, however, many producers employ the G and G laboratory chamber tests for reliable exposure results in shorter time periods. Florescent vs. Xenon Arc Testing Weatherometers used in the G and G tests approximate performance via intense exposure to the damaging elements in sunlight.
By blasting a product with UV rays, a weatherometer can simulate exposure results. In the ASTM G test, xenon arc lamps simulate full-spectrum sunlight within a controlled test chamber. Element provides both types of tests at our ISO accredited testing laboratories. Because xenon arc light is most similar to natural sunlight, we generally use the ASTM G test for outdoor weatherization testing.
Our team understands that florescent light has lower correlation to sunlight than xenon arc light; therefore, we generally recommend using the ASTM G fluorescent test to test for interior exposure i. Overall, this test involves 21 days of exposure. In ASTM G testing, UVA bulbs create the best correlation with outdoor exposure, as they have the closest wavelengths to damaging natural light from to nm. Different UV bulbs are useful for different testing purposes.
Therefore, these bulbs are useful for testing interior applications. UV-B light accelerates the brittleness that materials, particularly polymers, may suffer as they age indoors. In contrast, UV-A bulbs have a propensity for accelerating color fading and yellowing. If the aim of testing is to boost color fastness, UV-A bulbs are ideal. Our Engaged Experts can help you select the best UV bulbs for your testing purposes.
Exposure Testing Considerations It is impossible to recreate nature in the lab. Every location on the globe has its own unique combination of damaging elements, such as pollution, salt spray, and biological attack. Without testing in a specific location over a number of years, it is impossible to perfectly predict product response.
As such, the ASTM G and G tests produce comparative, not absolute data, but these comparative evaluations can still prove extremely valuable to designers. For instance, a slight shift in formula may produce twice as much resistance to weathering.
Such outcomes cannot be quickly obtained in outdoor settings; therefore, these weatherization tests are invaluable in timely product development.
Recreate specialized conditions with filters. In xenon arc testing, different optical filters may be applied to shift testing conditions for daylight, window glass, or extended UV spectrum exposure. Include a control, to act as a weatherization standard. ASTM International recommends that a comparable material of identified performance a control be exposed at the same time as the test specimen. This allows for accurate comparison.
Remember, these accelerated weatherization tests cannot exactly reproduce outdoor conditions, as they cannot account for altitude, seasonal variations, local geographical features, and other variables.
Control samples and multiple material samples produce the best comparative data. There is no easy exposure formula. As a general guide, hours under UV-B bulbs is equivalent to 1 year of exposure in South Florida, while hours under UV-A bulbs can create the same exposure effects. However, there is no simple equation for calculating exposure. It may be tempting to assume that shorter wavelengths, continuous exposure, high temperatures, and other variables can result in more intense acceleration.
However, each of these variables brings uniquely inaccurate results. For instance, constant exposure with no temperature cycling fails to recreate the expansion and contraction stress that materials face in outdoor locations. Element has been helping companies make Certain for over years. We can work with you to ascertain the most cost-effective, accurate testing approach for your material.
Costs for weatherization testing will vary according to a number of factors, including moisturization, sample size, number of cycles, and more. Find related articles to you through the Nucleus making certain for nearly years More from Element.
When rays of sunlight—particularly UV rays—bombard a surface, they degrade smaller pigment particles, changing the surface color and creating a chalky effect. Cracking, peeling, de-glossing, oxidation, and tensile weakening are additional outcomes of exposure; sometimes such deterioration can even occur through window glass. Moisture takes its own toll on surfaces, and the combination of sunlight and moisture can amplify damage, costing millions of dollars of depreciation each year. The ASTM G and G tests empower manufacturers to design products that can withstand exposure to sunlight and moisture. Ultimately, the most realistic way to test for weathering is to allow the product to degrade in real time, with outdoor testing panels.
More G Typically, these exposures would include moisture in the form of condensing humidity. Exposures are not intended to simulate the deterioration caused by localized weather phenomena, such as atmospheric pollution, biological attack, and saltwater exposure. Alternatively, the exposure may simulate the effects of sunlight through window glass. Warning—Refer to Practice G for full cautionary guidance applicable to all laboratory weathering devices.