Archival Printing - A Guide For Photos, Giclee & CanvasTuesday, October 20, 2009
- Although photo paper is considered one of the crucial archival elements for photographs, just archival paper will not help much.
- Ink and paper work together. You need the combination that works best giving you the quality output and the life you want.
- Depending on what substrate you choose, the same ink will last for wildly differing lengths of time (by as much as 70 years!).
- Archival ratings given by the manufacturer are the very best that you can expect. Unless framing and display are perfect you will get less.
- Some paper manufacturers loosely use terms such as "archival quality" without making any promises for image permanence or giving any detailed information.
- Generally for archival prints you need a pigment printer. Most inkjets use dye based inks with a life of 10-15 years.
- Traditional chemical prints are only good for 20 or so years for colour, 60 or so for B&W (providing good paper and washing technique
- Sometimes the "archival" claim refers just to the fact that the paper is acid-free, as acid-free paper lasts longer than other papers.
- It's always best to keep digital copies of pictures on a CD or DVD.
- Labs test for image longevity based on exposure to light, heat, humidity, water, ozone and air pollution during display (glassed and unprotected) and in dark storage (ie in an album)
- A procedure called accelerated fading is used to test for resistance to light exposure. This involves exposing images to intense light and using math formulas on the results to project when the picture might degrade to an unacceptable level.
- Wilhelm Imaging Research is the main independent third party for testing the archival qualities of prints
- Also known as digital lithography, archival inkjet prints, pigment prints and archival pigment prints.
- Giclee prints are usually created using professional 8-Colour to 12-Colour pigment ink-jet printers.
- This style of printing combines professional grade large format printers with archival pigment inks and acid free watercolour papers or canvas. The use of custom profiles, precise colour correction and expert scanning results in subtle gradations and many colours that would be out of range with other technologies.
- As no screens are used the prints have a higher effective resolution than lithographs.
- Artwork can be reproduced to almost any size and on various media, giving the artist the ability to customize prints for a specific client.
- Giclee prints evolved from Iris prints which was a 4 colour ink jet printer line pioneered in the late 1970s by Iris Graphics. This technology was first developed as a proofing process for digital prepress. Giclee prints are now way more sophisticated than Iris prints.
- Special inks have been developed for giclee printers that provide better colour accuracy, expanded colour gamut and longer life of the print. Giclee inks resist fading 10 times longer than those used in Iris prints.
- More affordable than lithographs. With lithos, you have to print and buy all of the prints at once. With giclee prints, you can print a small run or you can print one at a time as you sell them. You can have little to no inventory, so your startup costs are much less.
- When choosing a giclee printer, check that your proofs are printed on the final output substrate (i.e. canvas or watercolour), not generic proofing paper.
Dye & Pigment Based Inks
- Traditional chemical based colour photography has always used dyes in its films and print material. It has not been commonly possible to use pigments in colour photography.
- Dyes are dissolved in the ink vehicle or dispersed in the image-forming layer at the molecular level itself. They are very, very small particles. Pigments are insoluble and are much larger particles.
- Pigment ink in general has better light stability than dyes due to their larger size and good water-resistance. They are also usually much more resistant to ozone, or gas fading.
- Short term drift is a measure of the amount the printed colours change over time after the initial drying.
- Pigments have very little short term drift. Dye based prints tend to drift more.
- Right now (2009) there isn’t a perfect high gloss paper solution for pigment based inks. There are top quality gloss papers for image permanence, but they display differential gloss.
- Differential gloss is when the gloss of the image is to some degree a function the density of the ink. In other words, the glossiness is uneven. Traditional colour photographs don't have this problem. Neither do dye based prints.
- Differential gloss is less noticeable in an image when it is displayed under glass.
- For large prints and fine art prints, a semigloss or luster finish is often preferred or looks better than a full gloss anyway.
Choice Of Paper
- Especially with dye based printers you need to be aware that your choice of paper can have a huge affect on the print's permanence. It can be the difference between two and 72 years. It can be that dramatic.
- To be sure of print permanence, pick a printer for which print permanence data is available, for the ink and media combinations used for that printer. The manufacturer should also have a detailed description on how the tests were done.
- Manufacturers often publish data just for their paper that does the best, even though they have additional papers available.
- By using the exact ink and paper combination tested and rated, you can achieve the same kind of archival image stability.
- The papers made by third-party companies, not the printer manufacturers themselves, are not optimized for any particular ink set or printer. They are a one size fits all approach and that means that they don’t fit any well compared to the printer manufacturers who design their papers specifically for their ink sets.
Swellable & Microporous
- There are two basic technologies used in high end papers, swellable and microporous.
- One easy way to distinguish between porous / microporous and swellable papers is that if the paper package says "instant dry" then it's very likely to be a microporous type.
- Another way is the squeak test. Just rub your finger across it and if the paper feels like it squeaks and somewhat grabs your finger, it is the microporous type. The paper is so absorbent that it absorbs the tiny traces of oil and moisture off your finger, which act as a lubricant on smooth surfaces.
- Swellable is the older technology. The swellable ink jet papers use an ink receptive coating on the surface that is more akin to traditional photographic gelatin. A gelatin layer was used to "swell" when the water based ink made contact, then dried to form a protective barrier from atmospheric contaminants. But the gelatin is susceptible to all forms of moisture, and are highly unstable in a humid environment. Even a sweaty finger will ruin the print.
- Research moved from gelatin to silica. Silica coatings form small pores that trap the ink, letting the water evaporate quickly. This is the basics of the technology of the "Instant Dry" and "Water Resistant" media. Most media today are micropore.
- The major disadvantage with instant dry papers is atmospheric contaminants. These coatings offer no protection from ozone or other airborne contaminants. If the printer is using dye-based inks then they are probably printing on microporous paper which has a high susceptibility to ozone.
- Now gelatin is ONE of the polymers frequently used in swellable papers, usually in combination with others. When the ink hits the surface of the print the image receptive coating actually swells up. In areas of high-density ink coverage it can take a number of minutes, or even longer, before it actually feels dry to the touch. The ink is absorbed into the swollen layer and then, as the water evaporates, it shrinks back down to its original surface thickness with the dyes or pigments to some degree encapsulated in it. That encapsulation provides a significant amount of protection from the ambient atmospheric gases.
- Traditional B&W photos have an image composed of pure metallic silver under a gelatin emulsion. If it wasn’t for the protective effect of the gelatin emulsion and the overcoat in which that silver layer resides, B&W photos would only last a day or two before the image would become stained or discoloured.
- If you are using a swellable or instant dry media, your print still needs protection.
Fine Art Rag Papers & Canvas
- Cotton paper is naturally acid and lignin free. It is 10 times stronger than pulp papers. Most fine art papers and canvas are made from cotton as it has the potential to last up to 500 years. Acid-free paper lasts longer than other papers.
- Cotton rag papers can be divided based on surface and recommended black ink type. There are those that are matte and use black ink. And those that have a semigloss coating and allow the use of the richer and deeper photo black ink.
- Prints on fine art rag papers look VERY different to luster and gloss papers. They have a relatively weak Dmax and a reduced colour gamut.
- The Dmax is the darkest black (measured as an optical density) that a printer can output or that a paper can provide.
- The big difference among rag papers is the surface texture. There are huge variations in the surface texture from no texture at all, to very textured.
- Smooth rag papers make very sharp, relatively high contrast prints, the more textured papers are less sharp and usually have less contrast.
- A textured paper surface provides a beautiful soft 'painterly' look to prints, and especially with large prints, adds interest and apparent detail to things like snowy landscape.
- When matte paper is framed behind glass it looks a little bit glossy. The differences between matte and glossy papers are not so great when they are framed. The mediocre Dmax and gamut are also not as apparent. And there are no under glass reflections with a matte surface.
- Matte papers can be coated with various spray coatings which make them look glossy and increase the contrast.
- Cotton rag based papers with semigloss surfaces allow the use of photo black ink. This improves their Dmax to rival the plastic luster papers.
- In general, for archival properties with the least image change, choose un-brightened, non-OBA papers.
- Fine art reproduction is usually more pleasing on a matte surface than any other.
- Many digital papers have coatings which enlarge the paper's colour gamut and Dmax. These coatings are prone to scuffing and scratching and reduce the archival properties of the print.
- ISO 9706 sets the standard for galleries and museums for age resistant papers.
- Unfortunately the ISO 9706 does not take OBAs into account and these additives are known to deteriorate in time.
- OBA stands for Optical Brightening Agent. They are chemical additives used to enhance the colours printed on the paper and have an optical whitening effect on the paper.
- After being exposed to light for a time OBAs will lose their fluorescent properties, leaving the natural colour of the paper and less vivid printed colours. OBAs tend to fade quickly and make the paper appear to be yellowing. The paper can end up looking like cheap acidic paper even if it's acid free cotton.
- If you choose a paper whitened with natural pigments instead of OBAs, the colour you see on the first day of printing will still be the same in 50 years time.
- Traditional black and white RC (resin coated) prints also suffer from deterioration in which oxidants generated by the top plastic layer of the paper attack the silver image below. This does not happen with fiber based black and white prints.
Protection - Varnish & Glass
- Susceptibility to ozone is a large problem for prints that may be exposed to the atmosphere for long periods of time.
- Ink jet media has a receiver layer on the top of the substrate that acts like a sponge. Ink jet inks are water based, and when sprayed into the receiver layer, the layer absorbs the ink. Even when an image is on the media, the receiver layer still acts like a sponge, and will absorb all moisture, fingerprint oils and atmospheric contaminants.
- It is strongly recommended to either frame an ink jet print under glass or seal the print and keep it out of direct sunlight, even those on high quality fine art paper.
- Canvas prints are often coated with a protective varnish so that they can be displayed in the same manner as an oil painting, without glass.
- Adding a protective varnish can add 10 to 100 years to the permanence rating of a print. http://www.premierart.info/pdf/press/WIR_Seal_PR_for_Press.pdf
- Using a UV blocking glass vs plain optically clear glass when framing can double the permanence rating of a print. http://www.wilhelm-research.com/canson/canson_infinity.html