Inkjet Pigments and Color Longevity
Initially inkjet prints in the early 1990s, like the Iris or Colorspan inksets, utilized unstable dye colorants. In a broad sense, dyes are smaller and less complex molecular bonds that can fade easily when exposed to daylight. Pigments as a class of molecules are composed of much more complex larger molecular bonds that can hold up quite well in daylight. Early inkjet pigments could be somewhat dull in comparision to the gamut of dye inks, but that's no longer the case. Amazing progress in both permanence and color intensity has been made in the last decade. But there are different kinds of inkjet pigments on the market today, a lot actually, some of them great, some of them very good, and some not so good depending on what may or may not be added to them. Since the mix that goes into various brands of pigments is proprietary information, usually patented, the only way we can possibly know how they compare to one another is to have them tested by third party testing labs.
Our most recent pigment printers, the 44" Canon IPF 8300 with Lucia pigments and the 44" HP Z series printers with Vivera pigments, have much improved potential longevity over any traditional color chemical photographic process such as type C, Cibachrome or dye transfer as examples . A color framed print from this configuration printed on Canson rag media is rated at 384 "Wilhelm years" in daylight for 12 hours a day in normal viewing illuminaation of 450 lux with its built in uv filter encapsulaed Vivera inks, and 199 years with our post sprayed uv coat with the Canon Lucia color inks. Black and white prints from the Vivera and Canon Lucia inks, using only the carbon based channels show much greater longevity. We always suggest that our clients become familiar with Wilhelm's test data since this organization is a major consultant not only to Epson, HP, Canon, Microsoft, etc, but also to various international museum conservationists, the American National Standards Institute, and the Museum Of Modern Art NY among many others. Tests have been completed for all the most common HP, Epson, and Canon inksets and oem media, as well as traditional processes like Cibachrome and Type C print technologies. It is important to realize that the degree of permanency, fade, color shift, etc, is greatly effected by many factors, including media type, optical brighteners present in that media, the degree and intensity of daylight illumination, long term relative humidity, and whether or not the artwork is being protected by glass or plexi, or a uv coating over time. Protecting the surface of an inkjet pigment print (or any print) is the single most important thing you can do besides selecting a quality paper/ink combiation in the first place. That is especially important in the case of coated inkjet media that can act as a sponge for absorbing alll kinds of toxins from the environment. Our company has always considered the stability of media and the inks we use to be of a major consideration in everything we do. We rationalize Wilhelm's comparative data as a method of comparing one brand of color output to another and view these relative annual figures as one way of comparing this set of inks in a comparative way to another. His end point refers to "easily noticable" differences in the orginal and the exposed excellerated print test.
Image Engineering in Germany has documented through their excellerated fade tests, very similar relationships as Wilhelm between the fade figures of the leading color pigment brands on the market. However their figures are lower in total projected "years of display" due to the fact that they are not testing behind glass and are using harsher bluer illumination sources. But the relationship between brands of pigments and their comparison to type C and Cibacrhome remains the same as Wilhelm.
In addition to Wilhelm Research as a reference point, we are now very happy to see the emergence of a new, far more interesting and totally independent testing facility, Aardenburg Imaging, to be testing the inks and media we use. Directed by Mark McCormick-Goodhart, a leader in the scientific print imaging community, his organization is the co-developer of the more accurate and more useful I Metric system of print longevity testing. And, unlike other such organizations, Mark is not being funded by the big inkjet corporations like Epson, Canon, and Hp. He is doing this very detailed testing solely from the support of individual end users, who may submit samples of paper/ink combinations of their choosing. Mark is giving us a lot more information about all of the factors of print fade and color shift than is published on similar website charts, especially in regard to paper stability. New tests for all the major brands of pigment inksets are in progress. We will contunue to monitor his results and compare that to Wilhelm's already published data. Mark's methods reflect a "noticable" difference to the human eye along with direct sequential comparisions between the unexposed and the exposed test print. Unique to Aardenburg's methods is the ability to see from his published color charts and individual color and tone patch data, exactly the impact that optical brighteners contrubute to the ultimate daylight exposed color and potential stain of various papers white base that can change the light values of an image. In other words, not all papers and their whiteners are created equal, and without Aardeburgs published tests none of us would have any concrete knowledge about the various manufactures papers as they are used with different sets of pigments and vice verca.
Anyone interested in learning more about the Aardenburg testing methods and seeing the results of his ongoing tests on a wide variety of ink/media combinations should join his website and learn how to use it. If you are a company please consider sponsoring him with a donation as a corporate sponsor. As new papers and ink combinations become available, we are hoping this website and his organization will become the defacto standard for communicating this kind of valuable information in the near future. This is as precise as it gets for this kind of info and we are all lucky to have it.
Check it out at http://www.aardenburg-imaging.com, follow it and please donate a contribution if you like what you see.