Dye inks and safe display conditions
At what cost fade?
In May of 2011, a collector paid $3.9 million dollars for Cindy Sherman’s Untiled #96, a chromogenic dye print (C-print) already exhibiting signs of fade and color staining. C-Prints have a tendency to fade in light, in the presence of high humidity/temperature. A third phenomena of C-Print is the un-coupling of certain chemical bonds that produces yellow staining. Nothing can actually stop this process including cold dark storage.
This iconic photograph by of the most controversial photographers of our time is also an important example of analogue color photography. Decay in this regard is art. Its declining existence appreciated. Displaying it is destroying it. But, to not display it or to attempt to stave off its chemical decay by keeping it hostage in cold dark storage (where no one sees it) would be an art crime, even as it would be a futile attempt to prevent it from self-destructing.
Yet, labs are still processing chemical dye color images for photographers who could make the choice of inkjet printing with pigment. Why then do dye chromogenic prints persist as a choice?
The answer is mainly in aesthetics. Many photographers simply prefer the color saturation of chromogenic printing, and the way C-print absorbs and transmits light. It is more of a felt sense. For many, color inkjet is still too literal. Light is the main ingredient of photography, and too much of it is not a good thing when it comes to longevity. The C-Print medium has improved its stability in modern times with Fuji’s Crystal Archive process. It persists.
Dye inkjet prints do not have the same chemical fading that C-prints have. Dye inkjet prints if printed on archival paper, stored in a archival conditions, and displayed in museum conditions can be archived for many times longer than can a C-print (even a $4 million C-print). Most if not all of the IRIS prints produced at Cone Editions from 1990 to today on uncoated fine art papers are significantly more archival than C-prints and potentially more archival than EPSON Ultrachrome pigment ink on EPSON Exhibition Fiber paper.
The “potentially” is because while EPSON pigment inks have significantly greater fade resistance than any of the IRIS ink formulations, EPSON Exhibition Fiber paper is pre-coated (like all inkjet papers) and will continue to absorb atmospheric pollution and harmful gasses over its lifetime. It is loaded with OBAs that may eventually stain the paper. It is made from wood pulp rather than acid-free, lignin-free cotton. This particular popular paper may make a pigment inkjet print difficult to preserve as long as the longevity rating of the ink. There is “archival” and there is “fade resistance”.
But many dye and pigment photographs and fine art prints are often displayed without an understanding of safe display conditions and perhaps not enough understanding of display life ratings. Dye is especially susceptible to fast fading in strong illumination. It can be displayed for longer time in low levels of illumination. There are standards and best practices guides for collectors that are often available from museums. These pamphlets caution against too much display illumination with the recognition that every photon of light that strikes dye or pigment diminishes it in some way. So, it’s important to understand what safe and unsafe display conditions are.
Many indoor locations are unsafe for dye inks
Kodak indicates that 120 Lux is the limit of safe display conditions for dye color photographs and that 90% of all color photographs are displayed in 120 Lux or less. Wilhelm indicates that 450 Lux is the limit of safe display conditions for color pigment photographs. An interior room in a house lit indirectly by incandescent light is considered to be 120 Lux. Museums are limited to 50 Lux (for comparison). Bright offices are about 450 Lux but often much brighter. A print displayed at 450 Lux has only 25% of the longevity it would have if it were displayed at 120 Lux. A print displayed at 5000 Lux would have less than 3% of the longevity it would have had it been displayed at 120 Lux.
A good perspective to keep in mind in comparing dye inks to pigment inks is that it would take years to damage a pigment print displayed in an unsafe condition, whereas the same display condition might deteriorate a dye print in just weeks. Another perspective to keep in mind is that museums display at 50 Lux or lower and although much dimmer than a safe display condition of 120 Lux, it is more than adequate for viewing artwork. Galleries, because they are trying to sell work, almost always display artwork in an unsafe level of illumination. They are terrible examples to follow if you wish to preserve the artwork you purchase from them.
Is dye or pigment right for you?
The differences between dye and pigment (and there are many) can be summed up in a few qualities. Dye is more brilliant in color. It is glossier. Pigment has better light stability. Dye is a long chain of engineered molecules that are held together in a delicate balance and are soluble in ink base. Pigment is a solid material that though ground to extremely fine tolerances remains suspended as solid particles in a delicate balance in ink base. The delicate balance of the dye is that strong light can cause the molecular chains to unravel and cause rapid fading. The delicate balance of the suspended pigment is that over time or under certain weather conditions these particles can fall out of suspension causing a large amount of solid material to attempt to pass through the ink delivery system of a printer.
Dye is certainly not a substitute for pigment. Dye ink’s best allure is the extremely low cost coupled with trouble-free operation.
It is possible to buy dye inks from InkjetMall that can have a display life in safe display conditions for up to 30 years (InkThrift PRO) and over 60 years (InkThrift CL). Of course, ConeColor pigment inks would be the best choice for photographs and fine art – or the best choice if longevity (fading) is your primary concern. But, if your needs are for short term graphics, dye ink is perfect. It can be jetted at high speeds, is cheap, and can make the difference between profit and loss on tightly bid projects such as trade show graphics. InkThrift PRO inks are designed for rapid low-cost printing using expensive EPSON professional printers. InkThrift CL is designed for the Claria based personal photo printers that EPSON released for home users who print photographs.
How long a print lasts is the subject of much controversy. OEM’s boast significantly high numbers. Most OEM ink and media users believe that their prints will not fade for 100 years if the OEM claims that a specific ink/media combination has a longevity rating of 100 years. However, that is simply not what the OEM is actually reporting. What they are reporting is that at 100 years, the print will have so badly faded to a 35% loss, that anyone can easily detect the fade. The term “easily detected fade” is used to describe the endpoint that the OEMs are using for their fade ratings – and it is an industry standard endpoint.
The industry standard WIR Visually-Weighted Endpoint Criteria Set v3.0 which is used by all the major printer OEM’s to give their longevity ratings does not measure for fade in neutrals, flesh tones, near neutrals, near whites, mixed colors, saturated colors, the paper, etc. What the industry standard tests by Wilhelm do measure are simple densitometric changes in a 1.0 and 0.60 density patch each of cyan, magenta, yellow and three color black. When any one of these patches has faded about 35%, assumptions are made on all other possible colors and a longevity result in years is given for when the print will have faded about 35%. Oddly, and thinking back to Cindy Sherman’s C-Print that cost $3.9 million dollars…the industry standard testing method is still based upon the technology of cyan, magenta, and yellow dye layers from the days of chromogenic dye printing.
And it was in part the failure in chromogenic dye prints that fueled Henry Wilhelm’s passion for understanding longevity, and to develop a CMY method for predicting their longevity. The system worked for inkjet when ink sets were limited to four inks (CMY&K). Later in the 2000’s when complex inkjet ink sets were released that included light cyan, light magenta, light black (as well as other colors), Wilhelm stated that he had lost the ability to analyze color shifts in these ink sets by only measuring the cyan, magenta and yellow inks.
While a research scientist at Wilhelm Imaging Research (WIR), Mark McCormick-Goodhart (Aardenburg) invented the WIR i-Star, a new test method based on CEILAB colorimetry for evaluating the permanency of photographic images. The WIR i-Star uses a complex color target that is measured with a color spectrophotometer rather than with a densitometer.
The WIR i-Star is the most advanced method for evaluating the light stability of inks and making longevity predictions. Some of the other benefits of using WIR i-Star are that fade results for the first time can be compared in prints that use different ICC profiles (yes it makes a difference), or from cartridges that are in different stages of nearing exhaustion (yes it makes a difference), or to determine when the OBAs in a paper will affect the color appearance of an image (yes it makes a difference). Most importantly, the i-Star can be used to determine when fade will first be visible (about 5%), or/and when it has reached 35% fade, or/and many intervals in between.
Unfortunately, the OEMs are still not using WIR i-Star for their current longevity ratings. There is no way to know if that is by choice, request, the expense of performing i-Star, or because an i-Star would reveal fade levels far below the industry standard 35% and upset consumer expectations that have been established.
IMHO, replacing the current density based CMY testing method and target of WIR v3.0 with the color and luminosity based WIR i-Star target and measurement method but keeping the 35% fade point would be a great interim move by the OEMs. They could then give a fade rating based upon fade that can first be detected (about 5%) by visually trained humans and a second rating based upon when it is easily detected by any human (35%). An OEM longevity rating might be something like 13 – 120 years. It would force more of the responsibility on the consumer to read the actual data. The i-Star is also designed to give varying lengths of longevity in varying display conditions. The consumer looks up their needs within the data and has a clear idea of a display prediction for their display condition. Further, if they bias their needs on portraits, or black & white made with color inks, or very saturated color they will find that some media/ink combinations actually have better or worse results in these areas. It is as perfect a system as it is complicated.
Vermont PhotoInkjet began utilizing the Wilhelm Imaging Research WIR i-Star beta several years ago. By using i-Star, we are able to effectively evaluate what changes to individual color positions will do to the overall light stability of an ink set as it relates to the entire color gamut of a print. It actually helped us to develop our second release of a dye ink set (InkThrift CL).
We use the i-Star to make longevity predictions based upon the industry standard “easily recognizable fade” of 20% – 35%. We fade samples in 10 Megalux doses and take color spectro measurements. We continue giving 10 Megalux doses to the samples until the a 35% fade is recorded in at least 3 of the 30 patches. At that point, we consider the sample to have reached its endpoint regardless of how well the other 27 patches have done. We now use a late generation Atlas accelerated testing chamber that is filtered to simulate sunlight through window glass. The unit is temperature controlled (stays cool inside while generating tons of heat which we vent outside). The amount of light energy the targets receive is measured and controlled by a computer to compensate for fluctuations due to either electrical load or bulb decay. We use an automated x-Rite DTP70 measuring system. The DeltaE differences are calculated using X-Rite Measure Tool which compares faded targets to targets kept in safe dark storage.
The three following i-Star visual measurement sets are for InkThrift PRO and the newly released InkThrift CL ink sets. Two of the tests are conducted within the same time period (38 years at 120 Lux) reveal the superiority of CL (test II interim) over PRO (test I endpoint). Where Pro has faded to 22%-35%, the CL ink set is averaging only 12%-16%. Test III endpoint is of CL allowed to fade to about 24%-32%%. It reveals a much longer display life (up to 95 years at 120 Lux) to reach what PRO reaches in just 30 years at 120 Lux).
Display conditions affect longevity in a manner that is nearly linear. Try to adhere to the 120 Lux recommended by Kodak for the safe display of photographs. Refer to the below to get an idea of accelerated fading compromises due to differing indoor display illuminations at 12 hours per day.
50 Lux = equivalent to current safe Museum display lighting = 220% of display life rating.
120 Lux = safe indoor display conditions = interior room indirectly lit by incandescent light = 100% of display life rating.
500 Lux = brightly lit room = 24% of display life rating.
1000 Lux = very brightly lit room for task lighting, or office work = 12% of display life rating.
2000 Lux = typical gallery lighting = 6% of display life rating.
5000 Lux = sunlight entering through a window but not directly striking the print = 2.4% of display life rating.
10000+ Lux = sunlight directly striking the print through a window or skylight = 1% of display life rating.
Actual print stability will vary according to image, display conditions, light intensity, ICC profile, RIP or driver settings, humidity, and atmospheric conditions. Vermont PhotoInkjet, LLC and InkjetMall do not guarantee longevity of prints. Ratings do not estimate the durability of the media or paper itself. For maximum print life, display all prints under glass or properly store them in archival conditions, use uncoated acid-free and lignin-free paper for best practices.