ISO Working Group 3/Working Group 5 is working on methods for measuring color image stability, writing test standards for indoor light stability and outdoor durability. The subcommittee is also developing standards to address moisture fastness, ozone fading and heat degradation/dark stability.
The proposed ISO standard for indoor photostability would specify three test conditions: (1) cool white fluorescent lamps, (2) xenon arc lamps, and (3) tungsten filament lamps. These three light sources were chosen to cover a wide variety of indoor lighting conditions. Xenon arc lamps with window glass filters are the test condition of choice for photostability testing in the proposed ISO standard. It provides a better simulation of full-spectrum sunlight through window panes. The standard is in an early draft stage and probably won't be ratified and published for at least 1 to 2 years.
The ASTM D01.56 Printing Inks Subcommittee revised one of their existing test methods to address the photostability of printing inks. ASTM D3424, "Lightfastness and Weatherability of Printed Matters," specifies outdoor exposure behind Florida glass, xenon-arc and cool-white fluorescent light exposure with window glass filters, according to ASTM D4674, "Color Stability of Plastics." Under natural outdoor irradiation at 300–400 nm, the radiation dose is 1260 m], while under xenon arc irradiation at 340 nm, the radiation dose is 510 k]. Additionally, the ASTM F05.07 Inkjet Imaging Products Subcommittee recently approved and published in 2005 a new ASTM standard for photostability testing of digital inkjet inks. The standard is named ASTM F2366, "Lightfastness of Inkjet Prints Under Window Filtered Daylight."
There are several accelerated photostability tests to choose from, depending on individual needs. For example, fluorescent UV testing using cool white lamps in the QUV is suitable for simulating indoor lighting conditions. The xenon arc test with window glass filter is suitable for simulating sunlight through a window, while the xenon arc test with daylight filter is suitable for simulating direct outdoor exposure to sunlight. Natural outdoor exposure testing (i.e. direct and behind glass exposure) should always be performed in addition to accelerated laboratory testing to establish a proper baseline for end-use applications and service environments.
