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Canvas - How long will it last?
by Bruce Connelly, Giclee Media Supplies Pty Ltd

I am constantly asked how long a printed canvas will last.  The only credible response is – "there is no simply answer". While there are far too many manufacturing and atmospheric variables to give definitive answers, we now know many of the factors that influence the longevity of inkjet canvas.

Archival or Not?
 
The term "archival" is one of the most abused within the inkjet printing industry. It has come to mean that the base product is both acid and lignum free (<1%), a fact guaranteed by the majority of cotton and cotton/polyester base products.

Virtually all canvas products sold by reputable makers for inkjet reproduction are archival by the above definition, yet their makers know that virtually none of them will survive more than 100 years without noticeable fading unless they are liquid laminated or covered by UV protecting glass.

The early inkjet industry was plagued by the premature fading of dye based inks and considerable attention was paid to improving longevity. Pigment ink vastly improved the longevity of inkjet printing, including canvas products but unlike paper, which is usually protected behind glass, inkjet printable canvas is exposed to the elements.

Image
Spray lamination

Accelerated light fade tests are a good guide to the best possible longevity given the prescribed tightly controlled environmental conditions but their usefulness in real life is questionable. Photographers have known for many years that films suffered from "reciprocity failure" and that means that say 10000 exposures of a single frame at 1/10,000th of a second did not produce the same result as a single exposure of one second. The relationship between the variables is not linear.

The same is true of accelerated fade tests, which only consider only the effects of light and suffer from reciprocity failure caused by various gases in the environment. As an example the first photo quality desktop dye based printers were sold with longevity claims of more than 10 years using the manufactures glossy photo paper. Many of these prints faded within weeks to an orange colour without exposure to light.

The fading was caused by ozone, a gas prevalent in the domestic home and this was the first time that we began to understand the impact of the environment on inkjet print longevity. Since that time, I have seen many archival canvas and fine art prints that have faded in the dark. There are many causes and they include excessive heat and humidity, gas fading and faulty formulation of the inkjet coating material during manufacture.

The study of print permeance has been expanded to examine the effects of both ozone and humidity yet we still see both printer and media representatives doggedly regurgitating print permanence in terms of a single number of years when it is well documented that the real world experience for unprotected canvas images may be dramatically different.

In 2004 Michael Berger and Henry Wilhelm published "Evaluating the Ozone Resistance of Inkjet prints" which showed what many disgruntled inkjet printer owners already knew, that dye based prints could loose a staggering 33%-65% in density when exposed to household air in Boston USA for a mere 29 days.  These tests were conducted using the manufactures own papers and at 70% relative humidity and 24 degrees C, common conditions in Australia.

Image
Roller lamination

Under the same conditions pigment inks performed much better but they still lost 2% of their optical density over the same period indicating that 30% of optical density would be lost in 1.2 years, the Henry Wilhelm endpoint criteria. It was noted that the rate of air-flow over the printed surface heavily influenced the results. If we assume that unprotected canvas behaves like the OBA free fine art paper tested in Boston then the life of unprotected canvas products may be dramatically shorter than previously expected.

Burger and Wilhelm state:

"Often, but not always, an accelerated test can overestimate the stability and thus the predicted life"
Therefore accelerated light fade tests can only be regarded as a theoretical maximum for the specification and any prolonged increases in heat, humidity or air pollution over those of the test environment may dramatically shorten the display life.

When selecting canvas I suggest you pay no attention to unsubstantiated claims of longevity as almost all products are now acid and lignum free. The greatest risk to canvas longevity comes from chemical contamination from by-products of normal modern living.

The Great OBA Beatup.

One of the areas where the inkjet marketing spin doctors have been working overtime is the tenuous link between longevity and Optical Brightening Agents (OBA's). It is my assertion that any potential canvas purchaser should match the whitepoint to that required by the artwork and pay no attention to the OBA content of the canvas product.

OBA's are white or colorless compounds that work by converting ultraviolet light into visible light, thereby making the paper appear brighter or whiter. After being exposed to light containing UV rays for a long period of time, they begin to lose their fluorescent quality leaving the natural color of the base canvas and gesso. This means the base white will usually shift towards the yellow, a phenomena that can easily be witnessed by rolling a heavy coat of a deep UV blocking Giclee laminate over the canvas.

Many unscrupulous canvas vendors exploit this fact to imply bright white canvas will yellow to a degree greater than that of original product before the inks fade. The normally restrained German fine art paper maker, Hannemule was prompted to write in a recent press release:  

"So the claim that OBAs cause paper to yellow or reduce its permanence is simply wrong. Eventually, the perceived color of the paper will revert to the same base color as papers without; but initially, OBAs allow a much brighter base. It is not yet known how long the reversion to natural might take. We do know that it is not an immediate thing; it could take as many as 50 years (even longer if the artist takes measures to protect the image from the effects of UV rays.) But the point to remember is that the paper will end up the same color as it would have if OBAs were not used."

A study of Henry Wilhelm's test results show conclusively that fine art products with OBA's often exceed the print permanence of media that media where they are absent. The most recently published results for the Epson K3 inkset on the Epson 9800 show that Epson Watercolor Radient White, a paper with a considerable amount of brightener outperforms Epson's Ultrasmooth fine Art which has no such brightener.

We should therefore dismiss the claim that the inclusion of a brightener should influence canvas choice from a practical longevity perspective. There are many proven threats to canvas longevity not the least of which is the possibility of an unlaminated coating ceasing to adhere and crumbling on the floor.     

Liquid lamination.

Since the majority of microporus canvas products are displayed without the protection of glass, chemical contamination of the unprotected inkjet receptor coating is possible. The science of effective liquid lamination of canvas is one of the most sophisticated within the inkjet printing industry and there are few suppliers with effective solutions.

Image
Machine lamination
 
Since the makers of the receptor coatings seldom work directly with the makers of the protective laminates, a prospective purchaser of a liquid laminate should ask the supplier searching questions with regard to the chemicals suitability for the particular brand of canvas and ink and other general properties of the product.

Today, all credible suppliers of inkjet printable canvas products can make water resistant products that are suitable for environmentally friendly aqueous liquid laminates. When selecting canvas, I suggest only water resistant products are chosen and explosive solvent laminates totally avoided.

The major cause of canvas failure is chemical contamination of the microporus coating from cleaning agents or other agents present within our modern environment. While canvas and printer manufactures continue to hype artificial accelerated fade tests and make unsubstantial references to OBA fading, the giclee laminate manufactures have began to address the real issues behind canvas longevity.

Effective liquid lamination addresses both the attack by airborne chemical agents and adds considerable physical resistance to the canvas surface itself. It also tends to bind low adhesion inkjet coatings to the canvas avoiding the tendency of the image to disintegrate over time.

In addition a correctly formulated Giclee laminate should include a permanent UV blocking agent which is usually based on the suspension of rare metals in the substance, an anti fungal agent to reduce the risk of fungus in high humidity climates and a defoamer designed to reduce bubbling when sprayed or rolled onto the surface.

Giclee liquid laminates should not be confused with the pressure pack solvent sealers often seen in photographic stores. These sealers were not designed for canvas as they are mainly propellents and solvent, the resulting coating usually being too thin to provide an effective barrier against UV radiation or higher ozone levels.

Giclee liquid laminates are usually constructed of acrylic compounds or acrylic/urethane mixtures. Acrylics are usually preferred as canvas is displayed indoors and the extra strength and cost of urethane is normally not required in the home. There are different types of acrylics and the cheaper aromatic types should be avoided as they may decompose in far less than 100 years. Shopping at the local hardware store for an effective laminate should therefore be avoided.

When selecting laminates it is prudent to ask questions with regard to the chemical constituents, covering power and suitability for the canvas purchased. Ideally the canvas and laminate should come from a single source to maximize compatibility.


Conclusion:

Once the marketing hype which surrounds inkjet canvas longevity is discarded we come to the conclusion that for the majority of well made products it is the printers inkset that determines the useful life if a suitable coating is applied to keep the atmosphere at bay. Pigments have long been known to improve longevity but it took until 2002 with the introduction of Epson's landmark Ultrachrome ink that a suitable trade-off between longevity and color gamut was struck.

Henry Wilhelm's testing of the Epson K3 inkset on canvas shows that it does not perform differently to other unprotected matt stock and that longevity is more than 100 years when coated. Similar tests by Hewlett Packard using Lumina laminates and an HP 5500 with pigments resulted in more than a century using the HP Powertest criteria and even longer in Henry Wilhelm years. The preliminary results from Canon's new 12 color Lucia inkset appear to indicate a new benchmark in the longevity/gamut ratio has been set and canvas printing will benefit as much as any other media.

The potential for airborne containments to dramatically shorten the life of unprotected media is well documented and is the only factor under realistic user control. Put simply, if your canvas is left uncoated on the living room wall it is more likely to be destroyed by a domestic cleaner in the short term or cigarette smoke and cooking fat residues in the medium term than it is to experience UV light or hypothetical OBA fading.  

Regardless of the printer or canvas type you choose, the single most important thing you can do to prolong the life of the product is to coat the end result with a liquid laminate designed for inkjet canvas.   


References:

Hahnemuhle PRESSINFO – June 2006,  The Truth About Optical Brighteners in Hahnemuhle Paper

http://www.wilhelm-research.com/epson/9800.html

http://www.wilhelm-research.com/ist/ist_2001_10b.html

http://www.wilhelm-research.com/ist/ist_2_04_preview.html