QUV Testing and Pigmentation

Pigments are the key color ingredient in a coating formulation and can either enhance or degrade overall performance of the coating depending on their quality. No type of QUV testing is considered a good indicator of performance for coatings that use low-cost color pigmentation. Only natural outdoor weathering tests have been proven to detect the inferior performance that may result from the use of these pigments. Too often, detractors will use UVB measurements to make their inferior system appear to perform better. Real-world conditions are the only “truth indicator” of a system’s strengths and weaknesses.

QUV Lamps Weather Testing

Coated panels are placed inside a testing cabinet for QUV Testing. The two primary types of QUV Testing employ the same method for simulating dew and rain, using condensing humidity and/or water spray. However, the tests vary greatly in the spectrums of ultraviolet light used, causing markedly different results —no lamp captures the full wavelength of sunlight. Only natural sunlight and accelerated natural sunlight have that capability.

All QUV lamps emit mainly ultraviolet rather than visible or infrared light. They are equivalent to an ordinary 40-watt fluorescent from an electrical perspective. However, each lamp type differs in the total amount of UV energy emitted and in its wavelength spectrum. Fluorescent UV lamps are typically categorized as UVA or UVB lamps based on the wavelength of the UV output.

? QUV-A 340 Testing: Simulates the effects of real sunlight with fluorescent ultraviolet UVA-340 lamps, which provide excellent simulation of sunlight in the critical short wavelength region from 365 nm down to the solar cut-off of 295 nm. This type of UV lamp is recommended for QUV testing by the global ASTM G154 Standard. UVA-340 lamps are especially useful for comparison tests of different coating formulations.

? QUV-B 313 Testing: To speed up acceleration testing, UVB-313 lamps are used. They produce not only the shortest ultraviolet rays that the sun emits, they also emit unnaturally, short-wavelengths below what is found on the earth’s surface, which can produce anomalous results. This type of UVB light can initiate chemical reactions to occur in the coating that would normally not be possible under natural, real-world sunlight exposures. This testing has been proven to have poor correlation to natural weathering. It can cause failures in good-quality coatings that would not occur in natural sunlight and false positives in coatings that contain low-quality pigmentation.