The durability of digital prints is an important issue, with many paper manufacturers making claims about the longevity of prints on their media. This issue is vital if you want prints for display or to hand on to future generations because some ink/paper combinations are even more prone to discolouration than traditional photo prints.
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The durability of digital prints is an important issue, with many paper manufacturers making claims about the longevity of prints on their media. This issue is vital if you want prints for display or to hand on to future generations because some ink/paper combinations are even more prone to discolouration than traditional photo prints. The good news is that most inkjet prints should keep their colours and vibrancy much longer than colour photo prints. Many have been ‘lightfastness’ rated for more than 100 years.
Ensuring Stable Prints To complicate matters, prints made on some papers can take several days to finally stabilise – a phenomenon known as ‘short-term colour drift’. It occurs mainly with cheaper dye inks and can lead to uncertainty about what the final print colour balance will be. Regardless of which type of ink your printer uses, high quality, acid-free papers are more stable than standard papers, which is why they are used for all archiving and fine-art applications. Pigment inks are slightly more stable than most dye-based inks, although the differences have been reduced with the introduction of highly-stable dye ink sets in recent years. The most common cause of colour changes in dye-based inkjet prints is a change in the dye chemistry due to oxidation. This often results from exposure to ozone, which is common at low-levels in urban environments and reaches high concentrations around devices like refrigerators and air conditioners. (This is why you should never display unprotected inkjet prints on the fridge door.)   The above images show the fading that can occur when a print made with dye inks is displayed on a fridge door for six-to-eight months. Light can cause differential fading, particularly with cheaper magenta dyes. Cheap cyan dyes are most susceptible to chemical contaminants and, as they fade, prints turn orange. To obtain the maximum stability from your inkjet prints, give each print a minute or two to dry then cover it with a sheet of plain paper. Leave the covered print for at least 24 hours before framing it or storing it in an album. Inkjet prints last longest when framed behind glass or encapsulated in plastic (‘laminated’) to protect them against airborne pollutants. This is also a good way to protect traditional photos against light, dust and moisture – as well as airborne fungal spores. Don’t expect them to last as long if you stick them up on the fridge door – or in any other place where they may be exposed to ozone or other atmospheric pollutants.
Assessing Print Quality It is generally best to avoid viewing prints in artificial lighting as it can produce colour casts that may cloud your judgment. However, some photographers find a daylight fluorescent tube comes close enough to simulating daylight conditions – provided the viewing environment itself is relatively neutral. Here are some things to look for: 1. Fine (or not so fine) track lines across the print surface that indicate uneven ink deposition. Initiate a head cleaning cycle and re-do the print if this occurs. 2. An uneven surface texture. This problem is called ‘bronzing’ and indicates that ink has been unevenly deposited and/or absorbed by the paper. Cleaning the print head and reprinting the image may solve the problem but some ink/paper combinations are inherently prone to this fault. Try changing to a different paper for your reprint. 3. White patches on the surface of the image. This usually indicates dust on the paper surface before the print was made. However, if the print was made with pigment inks on paper with a textured surface, it could indicate abrasion as the print was removed from the printer. Re-print on a clean sheet of paper – and take more care with storage and handling of media. 4. Prints that are consistently too dark or too light or off-colour indicate your monitor is not calibrated to match your printer’s output. Recalibrate the monitor and make test strips until the print you make matches the image you see on the screen. If you plan to display your prints under artificial lighting you should also check how the print will look under the actual lighting conditions in which it will be displayed. Older technologies for producing pigment inks often produced inks that would look different under daylight, tungsten and fluorescent light sources, a phenomenon known as ‘metamerism’. Metamerism is rare in modern inks but prints made on papers with optical brighteners (see page 38) may still appear slightly different in lighting containing different levels of UV light. Consequently, you may need to make some slight adjustments to brightness, contrast and colour balance to ‘optimise’ the print for its viewing situation.
Optical Brighteners Because the natural colour of paper is very pale buff, OBAs are used in many inkjet papers. The white light reflected from the brighteners overwhelms the paper’s natural colour, making them appear totally white. The effect of the brighteners is to artificially enhance the maximum colour gamut and black density of the printed image. For prints of landscape and architectural photographs, in particular, both enhancements are seen as worthwhile. Prints of portrait photographs often look better on papers without optical brighteners where the natural buff tone tends to soften colours and contrast. Because they rely for their effect on UV light, OBAs work best under light sources containing a lot of UV, such as sunlight. Fluorescent lighting will produce different results, depending on the amount of UV in the light’s emission spectrum. Incandescent lighting emits very little UV so differences between prints on papers with and without OBAs will be minimal. Because of the way they work, OBAs decompose over time and the paper substrate reverts to its normal pale buff colour. You may be able to avoid this issue with over-coats that reduce the UV activation of OBAs, but their effectiveness has still to be proven. Consequently, prints made on papers manufactured with OBAs should not be seen as ‘archival’. To quote Henry Wilhelm from the Wilhelm Research Institute: “When long-term image permanence is an important consideration – or may eventually become an important consideration – fluorescent brighteners should be avoided”.
USEFUL URLs  Visit epson.com.au for the latest Epson printers.
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