Automotive exterior testing has been using back spray for years. It’s required in order to run SAE J2527, the performance-based replacement for SAE J1960. This is the only standard that we know about which requires this odd function. Although we do offer back spray as an option on our Q SUN Xe-3 and Xe-2 testers to meet this standard, one may still wonder: does the back spray function accomplish anything? Is it useful?
The answer to both questions is an unequivocal NO. Furthermore, back spray is counterproductive, since it wastes a lot of water and can at times even wash off specimen labels.
The back spray requirement in SAE J2527 provides a great example of the perils of hardware-based weathering standards. The original tester used in developing this standard was improperly set up for this back spray “feature” over 25 years ago, and its implementation via a hardware-based standard forced everyone to propagate this error. As a result, today we’re stuck with a standard that uses more than twice the water it should, can only be run in certain testers, and does not produce better results than front spray or condensation test procedures.