The ISO TC38 technical committee on textile has recently approved an important revision of ISO 105 BO2 (Colour Fastness to Artificial Light: Xenon Arc Fading Lamp Test) to make it a true, performance based standard. Until recently, the standard excluded flat array Xenon arc test chambers, even if they met the conditions and blue wool fading requirements of the standard. Now, like all other major international weathering and light fastness standards, flat array Xenon arc test chambers meeting the performance requirements of the standard are no longer restricted. This article tells the decade-long story about the change in and the benefits of the revised test standard.
In 2003, AATCC published a revision of Test Method (TM) 16, Colorfastness to light. That version was easily distinguishable from earlier versions because it replaced the letters of the cycle used (e.g., TM 16E) with numbers (e.g., TM 16-3) preventing confusion by the users of the test method. The fact that AATCC updated their standard wasn’t particularly noteworthy, since each AATCC and ISO test method is reviewed and updated every few years. What was noteworthy was that this revision marked a significant leap in technical content by replacing hardware-specific xenon arc apparatus references with detailed descriptions of the environmental test conditions. Some call these “performance-based” standards because they allow the use of any apparatus design delivering the appropriate performance conditions. All international standards bodies (e.g., ISO, ASTM, SAE, and AATCC) require that standards define the test parameters and test conditions; in essence, requiring that the test standards be “performance-based.” With the introduction of modern flat array xenon arc test chambers, which provided an alternative to traditional rotating rack designs, similar changes were occurring in standards for the paint, plastics, and automotive industries. Flat array test chambers may be preferred in many applications because the simplicity of operation and flexibility in accommodating three dimensional specimens (FIG. 1).
To illustrate the concept of hardware vs performance based standards, consider the following examples: the submission requirements for a magazine article. A hardware-based standard requirement might state that an article must be written on a Brand X laptop, using Brand Y operating system, and printed on a specific type of paper with a Brand Z printer. This creates an unfriendly environment for innovative laptops, operating systems, and printers, resulting in a reduced number of papers submitted. A performance-based requirement, however, might focus on the article being related to the textile industry, of at least 1000 words, and delivered electronically to the editor by a specific date. Hardware-based standards specify the “how,” while performance-based standards simply specify the “what,” leaving the “how,” up to the user.
For the textile industry, the use of standard blue wool test fabrics as an internal standard has been long established to ensure test chambers deliver the appropriate quality and quantity of light. Other control fabrics exist to verify test temperature and humidity. When it came time to open up TM 16 to flat array designs, use of blue wools made the process of verifying results from these testers a reasonably straightforward one. After seeing the results of a series of ring studies showing comparable blue wool fading results between various flat array and rotating rack testers, the AATCC committee on light fastness updated the standard.
By 2004, the last remaining hardware-based international test standard in the textile light fastness industry was ISO 105 BO2. This was despite ISO directives requiring the drafting of only performance-based standards. That year, at its meeting in Terrassa, Spain, TC 38/SC1/WG1 voted to conduct a ring study with the goal of including flat array testers in the standard. The society of Dyers and Colorists(SDC) agreed to organize the study, which ultimately included eight participants from five countries and a total of nine different models of xenon arc light fastness test chambers. These included a wide variety of tester models such as flat array band rotating rack testers, as well as water- and air cooled machines.
At the 2007 ISO TC38 meeting in Las Vegas, NV, USA, SDC presented the results of the study. The 2500 test specimens used made this international ring trial one of the largest light fastness studies in the history of ISO. ISO blue wool numbers 1 through 7, AATCC (purple) Xenon Reference Fabric, and red azoic standard humidity control fabric were all tested so that fabrics of low, medium, and high light fastness were represented. Significant among the findings were that flat array test results correlated with air cooled rotating rack testers better than water-and-air cooled rotating rack testers correlated with each other. Some anomalies were noted in the results, but none of them were related to the use of fat array testers. For examples, water cooled xenon arc testers produced more outliers than either air-cooled rotating rack or flay array testers. SDC defined outliers as test results the assessed grade was more than one full value from the mode. Use of humidity control methods other than the red azoic dye control fabric also created more outliers, and this group included the water-cooled rotating rack xenon arc testers.
Similar ring test were performed in China and India and these also concluded that flat array xenon arc test chambers delivered results similar to rotating rack designs.
At the 2007 TC38 committee meeting, the results were accepted by a unanimous vote. After extensive discussion, final vote amongst the worldwide TC38/SC1 members were cast, approving the change in 2014. The persistence and steady leadership of Wolfgang Schiller, from DEK, contributed to this successful conclusion. The updated version of ISO 105 BO2 was published in September 2014.
The performance-based re-write of ISO 105 BO2 was one of the most thoroughly-debated topics in the textile standards community in recent memory. Textile laborites around the world now have more choices than ever before regarding which type of xenon arc light fastness tester they are permitted to use (Fig. 2).
With the release of the updated ISO 105 BO2, one of the last hardware-based standards has been finally updated. The industry is now free to advance new and improved light fastness test products without the burdensome constraints imposed by non-performance-based standards. Looking forward, it will be interesting to see what innovations in light fastness testing the future holds.