Metal halide weathering test chambers have been used by Japanese companies for decades to reduce laboratory weather test duration. These companies have used products like the EYE Super UV chamber as a substitute for traditional fluorescent and xenon lamp chambers for standards compliance and screening tests, have obtained their results in a fraction of the time compared with the traditional tools, and produce results that correlate to outdoor and traditional tool test results.
Metal halide weathering chambers and the EYE Super UV were first developed in the 1980s, but were not promoted outside Japan until approximately 2010. Now the ASTM G03 Committee on Weathering is developing a practice for the use of the chambers (WK46431), and the US National Institute of Standards and Technology (NIST) has developed a version of the metal halide weathering test chamber.
The potential of the metal halide chamber to significantly reduce test time is driving awareness outside Japan. A chamber like the EYE Super UV combines a close spectral match to natural sunlight along with very high irradiance. The high irradiance when combined with responsible weathering test design has the ability to dramatically reduce the test time required with fluorescent UV or xenon testers.
The EYE Super UV produces 1500 W/m² of irradiance in the 300-400nm band. The user should therefore have a basic understanding of how their test subject material will respond to high UV irradiance when designing tests for the Super UV, and adjust the duration of irradiance cycles accordingly. For example, if a xenon chamber test requires 8 hours of irradiance the Super UV irradiance may be adjusted to 4 hours. Another benefit of the Super UV is that there is no additional heating of the sample material from far visible or near infrared light energy because the SPD is limited to 450nm.
Metal Halide Weathering chambers provide the same test control capabilities as fluorescent UV and xenon tester with the exceptions of using high irradiance energy in the 295-450nm band. This is summarized in the table below.
The potential to reduce test time is real, and the impact on schedule is significant. For example, a continuous irradiance test in a xenon chamber with a 10-year simulation goal may require 22 months to complete. The same test in the Super UV chamber may be completed within 4-weeks.
A user with a basic understanding of their material tendencies will have success conducting screening tests using the EYE Super UV when considering the material activation/reaction points based on specific spectrum, environmental conditions (temperature/RH%/moisture), color, and total UV.