Image Permanence: How archival are digital prints?
No photographic print can last forever, but responsible manufacturers are continually striving to improve the permanence of inks and papers so that photographic prints can last for generations even when displayed and exposed to light.
But if any company makes compromises to print permanence testing methods that artificially inflate longevity predictions, a new generation of consumers may see their precious memories fade, just as they have in the past.
The subject of image stability of color photographs has become considerably more complex in the last decade. As photography moved into the digital age and as more companies entered the business, the industry developed predictive print permanence tests that give better insight into how all prints, especially those displayed in light, will look to future generations.
Several factors affect the longevity of a digital print:
- Inks (dye-based or pigment-based)
- Media characteristics (coating, absorbency) of the material receiving the ink
- Environmental factors (light, moisture, and oxidation)
Dyes can interact chemically with coatings on papers—you should always make sure a paper is compatible with your inks. Many dye-based inkjet prints are susceptible to rapid, unpredictable chemical fading caused by oxidation from air pollution, especially in standard glossy or semigloss papers.
Dye-based inks are less expensive than pigment inks and tend to have larger color gamuts, but they are less lightfast and chemically stable. Early dye-based inkjet prints faded very rapidly—in months, but newer dye-based inks have much greater fade resistance—25 years or more when displayed under glass. Archival dye inks are stronger than ordinary dye inks, except when used on coated papers.
Pigments are tiny particles that come suspended in the solvent—that aren’t dissolved. Pigment inks tend to be more expensive than dye inks, but they are much more lightfast and chemically stable. Lifetimes are estimated at 80 to 200 or more years.
Early pigment inks had poorer color gamuts than dye inks (in part because pigments tend to be more opaque than dyes), but recent pigment inks are competitive. Early pigment inks also tended to clog printer nozzles, but newer pigment inks are much improved.
Pigmented inks are more resistant to fading and are not affected adversely by inkjet coatings. Epson is currently the only supplier of pigmentbased inkjet printers, but several independent ink manufacturers supply pigment inks (Luminous, Lyson, Media Street and MIS).
Because pure pigment inks have a difficult time achieving high Dmax (deep black), dyes are often added to pigmented inksets. Fortunately, black dyes tend to be more stable than colored dyes. Pigment inks which have zero dye components offer the most stability.
Cheap third party inks should be avoided, period. According to HenryWilhelm, who wrote the book on print longevity, none of them have decent longevity. Even worse, some clog print heads.
Not all third party inks fall into the "cheap" class. Several have been formulated for high quality, longevity, and/ or excellent B&W performance.
In the past several years Epson developed a unique micro-encapsulated technology for pigment-based inks in which each pigment particle is coated in resin, yielding an increased color gamut while retaining the excellent longevity characteristics of pigment inks.
Image Permanence: How archival are digital prints? This technology has resulted in an inkset called UltraChrome™, which has become the de-facto standard for the most discerning professional photographers who seek the highest image quality combined with the greatest print permanence.
UltraChrome™ inks deliver outstanding image quality and print permanence on a wide variety of papers, allowing end-users more flexibility and greater creative expression.
No longer can we think in terms of ink alone. The media, upon which the inks are printed, has an extraordinary effect on the longevity of inks. In effort to guide customers to quality inkjet supplies, the Wilhelm Imaging Research devised an Image Permanence Testing Program that certifies that any paper carrying the WIR Seal has been tested to have a display life of 25 years or more. An April, 2005 news release by Wilhelm Imaging Research, explained, "The new seal program provides an immediate, uniform test method to provide consumers with the information needed to understand the difference between various products used to print their digital photographs."
Over 90% of the market has agreed to the rating system: Canon, Epson, Hewlett-Packard and Lexmark are using Wilhelm certified numbers for their papers and inks. Several third party paper vendors, such as Ilford, Moab and Hahnemühle are also using the rating system.
The major non-conformist is Kodak, which maintains that the intensity of the testing light (450 lux) used by Wilhelm Imaging Research is not appropriate for the average home. Instead, Kodak testing uses 120 lux light, providing an entirely different standard of longevity. Until the International Standards Organization established a clear standard to follow, the majority of the industry is following the Wilhelm standard—based upon his reputation within the industry and the independent nature of WIR’s research.
The best papers for archival longevity are 100% rag or cotton-based and acid-free, though some non-cotton papers are quite long-lived. RC media can also have excellent longevity with pigment inks. Standard RC papers (not swellable polymers) and some coated art papers should be avoided with dy-based inks. Specific Print Permanence Ratings can be found at Wilhelm Research.
PremierArt™ Print Shield is a lacquer based spray for all ink jet prints that offers protection from light, water, moisture, airborne contaminants and even fingerprints. Testing by Wilhelm Imaging Research indicated significant increases in print permanence ratings.
Other manufacturers may promote a single ink and media combination that achieves a high lightfastness rating; but this high rating is often achieved with only one or two specific papers, and the prints, especially those made with a swellable paper, may be susceptible to damage with normal handling.
Other protective measures include covering the print with UV filtered plexiglass. As with any artwork, it is important to include a mat around the print to maintain a protective air space between the glazing and the artwork—preventing moisture condensation on the print.