Differences Between Instrument Types
Weathering instruments face the challenge to simulate irradiance, spectrum, air temperature, surface temperature, and relative humidity simultaneously with sufficient precision over the entire test area. Filtered xenon-arc devices come in various forms, including flatbed and rotating rack designs. Their sample areas range from 500 to 12,000 cm², and control technologies such as sensor type and sensor location differ considerably. Consequently, the precision, i.e. repeatability and reproducibility, depends strongly on the type of instrument.
Performance Checks of New Weathering Devices
Whenever you install a new weathering device in your laboratory, one of your first actions you should take would be conducting your typical weathering test with a standard reference material. Conducting such an instrument performance check will show you if your new instrument performs on the same level as your existing device(s). The new instrument should demonstrate comparable, ideally identical performance. In other words, cause similar or (hardly achieved) identical degradation of the tested reference material.
Standard Reference Materials
Blue Wool Scale, SAE Polystyrene Chips (PS), and ORWET standard reference materials are proven useful for conducting performance checks. While Blue Wool reference materials are extensively utilized for interior testing, particularly for color light fastness and hot light fastness evaluations, PS chips and ORWET plates serve both interior and exterior weathering tests. PS chips are particularly useful for gauging responses against the UV cut-on wavelength and temperature, thereby indicating potential discrepancies in Daylight filter quality. On the other hand, ORWET plates are useful as their coating reacts to UV, visible radiation, and temperature and is additionally sensitive towards moisture.
Delta E Comparison by Time and by UV Radiant Exposure
One of the easiest analytical methods for above reference materials is the measurement of their color change (Delta E) over time under your preferred test conditions. The appropriate measurement intervals should be chosen according to the test duration.
Best graphics for analysis include Delta E plotted against test time and/or Delta E plotted against UV radiant exposure. Below is an example of a PS-check conducted within two Ci5000 Weather-Ometers installed at separate locations running ASTM D7869.
Performance check of two Ci5000 Weather-Ometers running ASTM D7869 conditions using ORWET reference material on the middle section of the specimen rack
More Information
Where to buy? Blue Wool reference materials are available through your local ATLAS partner, SAE Polystyrene chips at www.testfabrics.com, and ORWET at www.swissatest.ch.
You find more information in our recorded online seminars on reference materials and lightfastness testing of textiles, or in our Technical Guide on color measurement.
For further information on other weathering testing topics, check our knowledge center or review upcoming webinars and seminars.