Wide-Format Inkjet Printing

In the last issue of the DP3 Newsletter we reviewed the new high-volume, commercial inkjet presses. In this issue we will examine the variety of wide-format inkjet printers. Wide-format printing has been around since the beginning of fine art and photographic inkjet output, as the IRIS Graphics printers, which were the first used for this type of output, created prints up to 34 x 47 inches. However, in 1993, wide-format drop-on-demand became available, and with it, a greater ease of use and lower cost compared to the IRIS printers. This was the beginning of the end for IRIS printers. The switch in drop-on-demand inks from dye to pigment in the year 2000 was the final nail in the coffin so to speak and the dye-only IRIS printers are very rare now.

But what defines a printer, or print, as being wide format? At first, any printer that created output wider than a desktop printer was considered wide format. Since the largest desktop printers output sheets up to 17 inches wide, anything above that would be wide-format. But things are not so clear today as printing equipment has continued to grow in size with the largest reaching 40 foot wide and capable of producing prints up to 150 feet in length! New terms such as large format, grand format, and super-wide have been added to the lexicon. While there is no clear agreement or standard within the industry on what these terms mean, there does seem to be an ad hoc consensus (though not everyone buys in) that wide format and large format are really synonymous and refer to anything between 17 and 60 inches wide, and that grand, giant, and super-wide are synonymous and refer to anything above 60 inches. The names don’t really matter on a technical level since the same printing technologies and materials can be used for either. For the purposes of this article, the term wide-format will be used to describe all of the systems.

That being said, the inks and substrates used in wide-format printing do differ from their desktop and digital press cousins. While wide format is sometimes used for photography and fine art, those are really just niche applications within the vast printing industry. Far more wide-format inkjet is being used for commercial signage and textile printing. These applications have different ink and substrates needs to ensure the quality and durability meets each end-user’s needs. This means that some very large fine art pieces or photographs may be made using different materials than smaller works.

Like desktop and digital press, wide-format uses either dyes or pigments as the colorants, but it differs in the number and types of ink vehicles that are used. The term ink vehicle refers to the liquid substance that carries the colorant from the nozzle to the paper surface. Below are descriptions of the variations currently being used:

1. In desktop and digital press, the vehicle is almost always water. After application of the ink, the water evaporates leaving the colorant behind to form the image. But the big problem with using water-based inks for many wide-format application such as signage and textile printing is that it does not hold up well when exposed to weather or washing. Aqueous inks are still used in many printers up to 60 inches, but above that specialty ink vehicles become increasingly more common.
    
2. Another type of vehicle is solvent. In this case, an organic solvent is the carrier liquid for the colorants. The solvent allows the colorants to bind very tightly to the substrate surface, and it evaporates quickly minimizing the time needed for the ink to dry. Its primary advantage is weatherability since prints made with these non-water sensitive inks are very resistant to rain and other outdoor eroding forces.
    
3. The sisters of solvent inks are eco-, mild- or low-solvent inks. These products do not use highly volatile organic compounds and are advertised as nearly as safe as water to the persons performing the printing. While, they are not as durable as traditional solvent printing, they are certainly better for the environment.
    
4. Another system used for signage is latex ink. This is not the latex as we typically think of for surgical or plastic gloves. Instead, it is ink that carries it own emulsion, which hardens into a thin film on the surface of the substrate when heated in the printer. The main advantage is that it can be applied to a very large number of substrates with differing surface textures and chemistries.
    
5. UV-curable ink is another coloring substance that hardens during printing like latex ink, but in this case by exposure to ultra-violet light. This type of ink is considered the most durable for use in the outdoor environment, as it is insensitive to water and highly resistant to abrasion.
    
6. Inkjet/dye sublimation is different from the dye sublimation process used for photo printing. In this system, an inkjet printer applies special sublimating dyes to a transfer sheet. The transfer sheet is then heat pressed against the substrate causing the image to cross over into the final substrate. In some newer sublimating systems the ink is applied directly to the substrate and then heated so that the colorant migrates directly into the paper, plastic, or textile.

In addition to the inks being different, there are also a wide variety of substrate types that are used in wide-format printing. Of course paper is used, but also plastics and textiles. The plastics can be opaque or clear depending on whether the print will be illuminated from the front or backlit like a theater marquee. A popular plastic for outdoor signage is polyvinyl chloride. Fabrics for printing can be either synthetic or natural fiber. For synthetics like polyester, the inkjet-dye sublimation process is used, while for natural fibers like cotton, ink is printed directly onto the fabric.

So why mention printing systems used for signage and textiles, when these types of objects are not as typically collected by institutions? Actually much advertising is collected, even in very large sizes, but the main reason is that many artists, photographers, and printmakers have been experimenting with these printers to produce either extremely large-scale pieces or for outdoor-specific works. They probably represent a much smaller portion of works being created and collected than aqueous ink prints, but they are still important and need care.

Unfortunately, little is known about how these materials will behave over time, or what the best practices for care will be. Certainly those that are aqueous-based ink on paper can be treated like the smaller versions, as the materials are identical. But for the rest, the ways in which these objects change and the relative effects of each decay force, such as light, pollution, abrasion etc., will be different. So while the manufacturers may tout these prints as being robust, until we have better experience with them in collections they should be treated as if they are as fragile.