Standards and Testing for Traditional and Modern Image Media
Transcription of the Archiving 2012 Session Keynote given by IPI Director James Reilly
While many if not almost all of the talks to be given in Archiving 2012 concern the acquisition and management of information in digital form, our keynote today deals with two topics firmly rooted in the preservation of human-readable, physical print media. In both topics we will contrast the situation two decades ago when silver halide imaging was the unquestioned leading technology for making reflection prints, with the current situation where silver halide is still widely used but three newer technologies—inkjet, electrophotography, and thermal dye transfer—are the primary methods in use for creating photographic prints.
One topic we will examine is testing, that is to say accelerated aging methods for predicting life expectancy when prints are exposed to stresses from heat, humidity, light, water immersion, abrasion, and air pollutants. Testing is something that we have done a lot of at the Image Permanence Institute over its 27 year history. For those of you who are not familiar with IPI (as we call it), we are a university-based, non-profit laboratory whose mission is research and education in the preservation of imaging materials and cultural heritage materials in general. We have a staff of 16 persons and are a department of the College of Imaging Arts and Sciences at Rochester Institute of Technology in Rochester, New York. We are co-sponsored by IS&T and we are very proud of that long association. We’re the only unit of RIT that actually has two logos on our letterhead and business cards. From the beginning in 1985 we have offered testing services as well as done grant-supported independent research on imaging materials. I will talk about how test methods have changed from the silver halide era to the digital print era. We are currently in the fourth year of a six-year, $1.2 million project, sponsored by the Andrew W. Mellon Foundation, to investigate the preservation issues of digital print technologies and compare them to the traditional benchmarks of silver halide chromogenic color prints and offset lithographic prints. We are also investigating the effects of ozone and NO2 exposure on inkjet prints with funding from the Institute of Museum and Library Services, a US Federal agency.
So, testing and indeed the value of testing for institutions, image makers, and society in general is one topic. The other topic I will speak about is one in which my own personal involvement predates even IPI, namely Standards—documents formed by a consensus of industry, governments, and consumers that are meant to define test methods, set specifications for performance, and guide the actions of institutions and individuals with respect to the permanence and physical properties of imaging materials. IPI’s testing activities and the standards creation process through the American National Standards Institute (ANSI) and later the International Organization for Standardization (ISO) have been closely interrelated, as IPI staff both learned from and contributed to the standards creation process. Dr. Peter Adelstein, who has worked at IPI for 27 years, has been the leader of many of the ANSI and ISO Committees. Special recognition should also go to Henry Wilhelm of Wilhelm Imaging Research, who was and is a key figure in both standards and testing methodologies. I tell you all this to establish my credentials to compare and contrast what testing and standards have meant to the world of imaging in the past, and what they mean now.
Let’s begin the comparison with the silver halide era. Twenty-five years ago testing and standardization was simpler (though at the time we didn’t think so). It was also more meaningful in guiding the understanding and practices of the imaging community. Why simpler? Because there were only a few colorants, image-forming technologies, and substrates to deal with. Our work was with photographic materials, which were clearly distinct from graphic arts materials (products of the printing press). We had black and white images with silver as the colorant and color images with chromogenic dyes as the colorant. All chromogenic materials used a standardized set of chemicals for processing. The industry was concentrated in a handful of large, vertically integrated companies (who now are either bankrupt, merged, shrunken, or altered beyond recognition—how sad for so many who spent their working lives in that industry).
The questions on everyone’s mind—how long will prints and films last and how should they be preserved—boiled down to defining the vulnerabilities of substrate, colorant, and image-bearing layer. Once defined, appropriate test methods could be developed and published in standards by ANSI and later, ISO. In the case of black and white images, there was a long history to draw on to define vulnerabilities: fiber-based substrates were very stable but the silver colorant was vulnerable to oxidation due to moisture reactive air contaminants. Ultimately, test methods for oxidation resistance were developed and published but found little application because the industry, which had long understated the oxidation vulnerability, had largely moved on to chromogenic color. Although it took more than twelve years for a standards committee to develop and publish a test method for the most important vulnerability of chromogenic color (namely, dark fading), the standard that resulted was one of the greatest success stories for both accelerated aging test methods and for the standards process itself. The tendency to fade and stain both in dark and light was so obvious a deficiency with chromogenic color products that the predictive test methods published in ANSI IT9.9-1990 changed products for the better and benefitted industry and consumer alike.
In the silver halide era, however, there were sometimes cases where the vulnerabilities were not so obvious—but were known to those who took an interest. One prominent example was the introduction of resin-coated paper supports for black and white prints. A standards committee took up the problem (which was that framed resin coated black and white prints exhibited rapid silver oxidation and image discoloration) but never found, or at least agreed on, a satisfactory accelerated test. Although to be fair, testing for this behavior was very difficult, it is my personal belief that industry representatives knew the entire class of products had this vulnerability and never participated in good faith in the standards process because it would hurt sales. This was not the most glorious moment for the standardization process, which always was carried out by humans whose livelihood depended on the commercial success of their companies’ products. However, in the silver halide era, the fact that there were fewer, more well-established players who all made roughly similar products in mostly similar ways meant that the archives and institutions that needed to know how to preserve images could get the answers from testing and standards. It was possible to form coherent preservation strategies around a general sense of what silver products and chromogenic color products needed to survive. IPI’s Storage Guide for Color Photographs, in which the leading print, negative, slide and motion picture print materials were brought together into a single overall presentation of life expectancy, made good practical use of the homogeneity that characterized the silver halide era.
Now we come to the present day and consider the saturation with prints made with inkjet, electrophotography, and thermal dye transfer technologies. Once again, the basic need is to define the vulnerabilities, develop adequate test methods, and publish standards to guide consumers and institutions. But gone is the homogeneity of colorant, substrate, and image-bearing layer. The industry has fractured and diversified, commercial interests are fiercer than ever and worst of all, the products and technologies change at dizzying speed. New technologies bring new vulnerabilities, but many of the old ones are still there. Product life cycles are measured in months, testing in years, and test material development and standardization in decades. The products evolve faster than the test methods that can discover their vulnerabilities and accurately measure the predicted performance.
What we have found in our own work at IPI on the new digital print technologies and by participating in the standards process through ISO, is that the enemy of useful preservation knowledge for those materials is their diversity and rapid evolution. Inkjet alone has two families of colorants, pigments and dyes; two families of image-bearing layers—swell-able polymer and porous coatings; and a truly wide variety of substrates from RC-like photo papers to fine art papers akin to water color paper. In some ways things are more hopeful. Freed from the constraints of chromogenic dye formation, color prints can be made with colorants that are extremely lightfast and dark-stable. This is especially the case with pigment inkjet products. In other ways, there is reason to beware new vulnerabilities: for example, pigment inkjet on porous papers are far more easily abraded than their silver halide predecessors.
Overall, the general concern about print permanence has shifted from the old light and dark stability of colorants to the physical and chemical stability of substrates. Some crack and peel under light stress or pollutant exposure or crack more easily, or become yellower in ways we do not yet understand. We are trying to assemble a set of general expectations about the permanence behavior of these new technologies but it is much more difficult because of the variety and complexity of colorants, substrates, colorant-substrate interactions, and never-before seen problems such as humidity bleed, poor water resistance, poor scratch resistance, and a tendency to abrade. These behaviors can be very specific and hard to generalize but some overall patterns are emerging.
Under the auspices of ISO Technical Committee TC42 Working Group WG-5, a number of new standard test methods for digital hard copy print materials have just been published or are about to be published. These include documents relating to dark stability, water fastness, ozone resistance, and humidity fastness. Close to publication are standards for light fastness and a standard test image target.
I think we should be grateful for the hard work done to create these standards (they have been worked on for more than a decade already) but let’s be realistic about the new world of digital imaging. Hard copy is still produced in large quantities but most images are never printed. When institutions are presented with the challenge of preserving hard copies for long time frames, the old paradigms have broken down. What exactly is this print object I have? Can I know its colorants, substrate, image-bearing layer, and be sure I am making the right choices for storage, handling, and display? We may have ISO test methods to measure a product’s characteristics, but those characteristics may be unique to that product. It’s difficult to identify even the broad technology used to make a given print. One example of the dilemma is the ISO Standard 18920 for color reflection print storage—the committee cannot resolve the general vs. specific problem to a degree where it can decide on whether to recommend cold storage or not.
More broadly, the very context for the testing and standardization efforts for digital print materials has shifted dramatically in the digital era. The same technologies are used for fine and applied photography and book publishing. Technology no longer identifies the application—is it photography or graphic arts or something else? In the past, photography had its own technologies and so did graphic arts, and they had their own test methods and standards. Now it is unclear how to organize and find the right context for such efforts.
Another major difference that is very apparent from the nature of this conference is that digital technology now underlies all the old categories of applications. What we are witnessing now is the complete recreation of approaches to archiving for the digital realm. This is something more than just the usual evolution of best practices and methods as new technologies become available, new lessons are learned, and libraries and archives adapt to them. It is a fundamental fact of archiving life that the pace of change is ferocious and therefore we have to reinvent everything far more often than we ever did. Indeed the evidence for this is that many of the issues to be discussed in this conference have been visited before, and will be visited again quite soon as digital technology evolves.
In closing, to return to the world of testing and standards for physical objects like hard copy print materials, we have seen it become much harder to accomplish because of diversity of products and rapid technical evolution, as well as confusion over which standardizing body should rightfully take jurisdiction. In the digital realm those same problems exist to an even greater degree. We certainly have no lack of challenges ahead of us. Thank you.