Age shall not weary them
By Andy McCourt
Since the dawn of dye-based digital inkjet reproduction, issues of colour fastness and print longevity have been at the fore. Today, with pigmented inks and non-wood fibre papers that are acid-free, claims of durability can run into hundreds of years. Andy McCourt looks at print archivability, and the test methods used to determine the claims.
Paper is an amazing material and some researchers have linked any civilization’s success to its ability to effectively produce paper. Looking at paper’s etymology – the name comes from papyrus, the reed used by ancient Egyptians to make a writeable, portable surface – it would seem so. Rome prospered under instructions and laws conveyed on vellum (animal skin) and parchment; China (T’sai Lun), invented true paper-making using a combination of pulped fibres and Europe prospered artistically and politically as its paper consumption escalated following the 15th century invention of the printing press.
|“Whereas books and art from the 1400s, such as the Gutenberg 42-line bible and Albrecht Dürer prints, have survived well in museums; many works on early wood-pulp paper have either crumbled away or are so fragile they are stored in virtual isolation from the 21st century.”|
Paper is made of fibres – mostly organic but there are synthetic alternatives. Plant fibres used over the centuries include hemp, kenaf, linen, flax, waste rags, cotton, straw and sugar cane bagasse. Where’s wood in all this? It may surprise you that wood fibre was hardly used in papermaking prior to around 1850. With the invention of the ‘Fourdrinier’ pulping process by Frenchmen who moved to Britain, wood fiber derived from plentiful and cheap trees rapidly became the main raw material of paper.
The downside was that wood made weaker (shorter fibre) paper that was prone to rapid deterioration, yellowing, insect attack and mold. Whereas books and art from the 1400s, such as the Gutenberg 42-line bible and Albrecht Dürer prints, have survived well in museums; many works on early wood-pulp paper have either crumbled away or are so fragile they are stored in virtual isolation from the 21st century.
We all know what happens if you leave a newspaper out in the sun even for a few hours. It starts to go yellow. This is caused by a photo-reaction with the lignin that remains in newsprint. Lignin is the polymer material that composes the cell walls and interspatial ‘glue’ of cellulose. Because most newsprint is made from mechanical pulp (i.e. the trees are chipped up, mashed up, ‘cooked’ and spread out as thin pulp on wire conveyors); much lignin remains in the paper, even if combined with de-inked recycled paper.
Chemical pulp – where various chemistry and bleaches are used – removes a lot of the lignin but it costs twice as much and some lignin inevitably remains and acidity levels can be high. Fine wood-based digital papers as used in art and photo reproduction on inkjet machines, invariably go through many refining stages where as much lignin as possible is removed and additives such as Kaolin, sulphites, oxygen, chlorine and sodium hydroxide used to whiten the paper.
It is generally accepted that, for art reproduction purposes, a cotton-rag acid-free paper is preferred. Cotton fibres are longer, stronger and low-acidity. However, this does not discount all wood-fibre papers from ‘archive’ quality. Acid neutralizers can produce wood pulp papers of pH7 and above – acid free. Of course, canvas is cotton anyway but care still needs to taken in selecting it as coatings can crack and peel.
CONSIDER THE COATING
For digital reproduction purposes, once a fine paper is manufactured, it is invariably coated with an IRC (Inkjet receptive layer), which maximizes ink density and image quality. There is a move towards uncoated papers where ‘sizing’ in the mill with starch or gelatin, or ‘infusion’ additives are used. Inveresk Mill’s uncoated Somerset Velvet has been used for years by DFA printers as it allows the true texture of the paper to remain but there is a trade-off in saturation and dot-gain (where the ink droplet ‘spreads.’)
IRCs are complex, sometimes up to 7 layers, and themselves should be acid-free for archival results. Some names to look out for in archival-quality art papers include Hahnemuehle, Canson, Arches, Ilford (Gallerie), Innova, Moab, Hawk Mountain, Breathing Colour, Museo, Crane and Bockingford. The major inkjet printer manufacturers – Epson, HP, Canon also have archival papers and these are often sourced from one of the abovementioned mills.
On the photographic side, the choice is huge with familiar brands such as Kodak, Ilford, Konica Minolta, HP, Epson, Canon and Fujifilm there along with diverse bands such as Intelicoat, Folex, Olmec, Mitsubishi, Sihl and others. Surface choices and weights reflect traditional photo paper choices with glossy, semi-matte, matte and silk. Generally the lower gloss surfaces exhibit better archive qualities.
A WORD ON INKS
Of course, the paper (or canvas) chosen is only one third of the archive equation. Ink is another third – and method of storage/display is the final third. Inkjet inks have improved enormously since the early dye-ink days where you could literally see the colours change in strong sunlight. Today, pigmented and enhanced dye inks last a lot longer before noticeable fading or colour shifts.
In their battle to keep the ink business away from third parties and refillers, the big inkjet printer manufacturers have resorted to intense R&D and branding to keep customers. Epson has its Ultrachrome K3 ink, HP its Vivera, Canon Lucia and Roland Pigment/Dye. It’s often very clever technology at the ‘nano’- level where miniscule pigment particles are ‘coated’ with UV-inhibitors to slow down the fading process.
WHAT ABOUT CHEAPER INKS?
Fierce debate abounds on the performance of third-party (and cheaper) inks over the manufacturer’s original. Whilst there are specialist ink makers producing Gicleé archival brews and special ‘Quad Black’ sets for monochromatic images, the consensus as indicated by research conducted by Wilhelm Imaging Research (www.wilhelm-research.com) is that the trade-off for lower prices is greatly reduced achievability – as much as 99%! This means if a print made with the printer manufacturer’s ink is rated at 100 years before noticeable fade, some third-party inks are rated at less than a year. Yes, if you go for unknown cheap refilled ink, your $500 Gicleé masterpiece could be a ghost image in a year!
That said; there are products from firms such as J-Teck3, Lyson, Eterna and ITL, for instance, that claim close performance results to original inks, at a lower price. The issue then becomes one of warranty and printer support in the event of a breakdown. The rule of thumb here is, test, test, test and if in doubt stick with the manufacturer’s ink.
HOW ARCHIVABILITY IS DETERMINED
One independent organisation has emerged as a world-leader in testing digital print longevity, and that is US-based Wilhelm Imaging Research. Conducted in a science-lab environment, prints are made, the printer-ink-paper combination noted and then accelerated light-fade test conducted for four different display situations, plus resistance to ozone and humidity.
Most leading printer manufacturers – except Kodak - now use Wilhelm to benchmark their offerings. His accelerated light-fade test is based on prints sustaining 450 lux of illumination for 12 hours a day. Wilhelm achieves this by exposing the prints to a 35,000 lux non-UV filtered light source, with 60% RH (Relative Humidity).
Kodak on the other hand, uses a less conservative test model, claiming it reflects real-life situations more. Its archive testing (which delivers results 3x-15x longer than Wilhelm’s) is based on prints being exposed to just 120 lux of illumination for 12 hours a day, and it uses a UV-filtered 80,000 lux light source with 50% RH.
Whether the more lenient Kodak testing method is any more representative of real life than Wilhelm’s (preferred by all other major manufacturers), will only be known by future generations, as some of the archive claims stretch up to 700 years!
PROTECT FOR LONGEVITY
One thing is very clear from Wilhelm’s testing and that is unframed, unprotected prints last a shorter time than glass or plastic covered ones, and those in photo albums. A typical result might reveal:
|Years before noticeable fading and/or changes in colour balance occurs:|
|Printer/paper/ink combination ‘X’ with Premium Semi Gloss Paper|
|Displayed Prints framed under glass:||85 years|
|Displayed Prints framed with UV filter:||98 years|
|Displayed Prints not framed:||60 years|
|Prints in album or dark storage:||200 years|
Looking at Wilhelm’s results shows that cotton rag papers and black-and-white prints made with special black ink combinations, deliver even longer archive attributes. Black ink is more stable than CM or Y as it contains a high proportion of carbon or ‘lamp black.’
Mention should be made of the various lacquers and coatings available to protect inkjet prints, such as Lumina coatings from GMS. Whilst Wilhelm does not routinely test these, there is no doubt they extend print life considerably, plus afford protection from ozone and other airborne pollutants.
THE FINAL WRAP
Moves are afoot in the UK and USA to formulate official standards for DFA (digital fine art) and photographic archive ratings. This is a daunting task as there are so many variables. Collectors, newlywed couples and galleries do not want to see their expensive digitally-produced images fade to nothing.
It is behoven on our industry to take extreme care in presenting products of high integrity that have been tested for durability. To achieve this the US Gicleé Printers Association have come up with Tru Gicleé™ - a logo that can only be used by members who have adhered to nine principles, as below:
The following are the GPA’s 9 standards for Tru Giclée™ printing:
1. The ability to exactly reproduce original artwork
2. The reproduction process bears no evidence of the technology used
3. The printer adheres to archival standards consistent with that of a collectable fine art print
4. The reproduction represents the highest quality product available to this culture, at this time
5. The printer fully discloses the products used in his art reproduction
6. The printer enjoys a generally recognised reputation for honesty and integrity amongst his customers and peers
7. The artisan producing (or supervising the production of the work) has been certified as a Master Printer by the G.P.A.
8. The printing company participates in an on-going research and development effort to improve his craft and the G.P.A.
9. G.P.A members actively educate customers and the industry as to the meaning and value of a Tru Giclée™.
All sounds good for us here too? Using the right printer-ink-paper combinations, and finishing your digital images for display and archiving using proven methods and materials, will ensure that age shall not weary them – and future generations will remember them.
Andy McCourt is a regular contributor to Digital Reproduction