Printing on Aluminum
This is a truly inspiring time to observe the evolution of printing, and the expansion of printing technology to create a bridge between fine art and commercial art.
I attended a craft fair this Memorial Day weekend and saw some striking photo prints on metal. I asked the artist for an explanation of the technology she had used, noting that I was a printing broker.
The artist explained that she had photographed the images with a digital camera and then enhanced them in Photoshop (many of the images were of ethereal female subjects with a romantic, Arthurian-Legend sensibility). She had then sent the digital photo files out to a commercial photo printer for rendering on aluminum, using a proprietary, dye-based technology.
Upon returning home, I researched printing on metal. I remembered that the artist specifically had said this was a dye-based process, not an inkjet process.
(I had assumed it was therefore a dye sublimation process, using heat to vaporize solid ink, thus turning it directly into a gas to be infused into the substrate. Using a separate pass for each of the cyan, magenta, and yellow dyes plus a coating, the dye sublimation process brings carrier sheets containing the dyes—one by one—into direct contact with the substrate, building a continuous tone image layer by layer. Unlike offset, inkjet, or xerographic printing, dye sublimation can deposit more ink or less ink, creating lighter or darker tones without the need for halftone screens. Unlike other digital and offset technologies, dye sub can therefore provide true continuous tone images—just like a photographic print.)
With this in mind, I found the Magna Chrome website, which sells images printed on aluminum. (There are other vendors selling similar technology.) I found this whole concept particularly intriguing for the following reasons:
- It reflects the increasing convergence between digital printing and the fine arts.
- The metal-imaged prints are more vibrant than any other digital prints I had ever seen.
- It was therefore clear that the substrate has a profound effect on the overall look of a photographic image.
- The images were scratch resistant and rigid, requiring no glass or framing prior to hanging. (This changes the nature of photo presentation and provides a more intimate and informal viewing experience.)
The Magna Chrome website described the technique as follows: “Special dyes are printed onto a transfer paper and then infused into a patented coating under pressure and heat.” The images are rigid, durable, and waterproof. No glass or frame is necessary, so glare is reduced. Furthermore, the depth of the patented coating gives a luminous quality to the photos and brilliance to the colors. The image seems to float within the coating.
So I learned that the image is not really printed on the metal. Rather, it is infused into the coating on the metal. The artist at the craft fair who had taken the photos noted that prints could be made on a white background over the metal (like painting on a canvas primed with gesso), or on the glossy, metallic surface of the aluminum.
Looking closely at the fine art prints at the craft fair, I could see that the white substrate brightened the colors.
The silver color of the aluminum plate provided an even more shimmering image. It looked as though metallic inks had been used within the photo, even though the aluminum substrate actually provided the entire sheen.
In both cases, it was clear to me just how much the substrate on which an image has been printed affects the overall look, as light reflects off the substrate and back to the viewer's eye, brightening the hues of the image.
The Magna Chrome website notes that the luminosity of works by painters such as Rembrandt was due to these painters' practice of applying multiple, thin layers of paint to their canvases. In the same way, the layers of dyes infused into the thick, translucent coating on the aluminum plates give a similar sense of depth and luminosity, often leading viewers to think the images are backlit.
A Printing Trick with White or Silver Ink
If you don't want to go the route of printing on metal, you can still learn something from this process that can be applied to offset lithography.
Starting with a dark substrate, such as a black text sheet, you can print white directly on the sheet as a ground (like gesso on canvas) and then retain the brilliance of offset inks laid on top of the ground (otherwise, the darkness of the background color will alter and dull down the bright hues printed on top).
As an alternative, ask your printer about mixing a little opaque white ink right into the offset inks. Remember that in offset lithography, the process colors are transparent, as are many other offset inks. Mixing opaque white into your inks can increase their ability to cover colored substrates. You and your printer may want to try an ink “draw-down” to see how this will look before putting the job on press. (If it doesn't work, you may need to use screen printing, which covers darker substrates more evenly due to the thicker nature of screen printing inks.)
In addition, silver ink can be used in a similar way to increase the brightness and luminescence of the overprinted ink.
[Steven Waxman is a printing consultant. He teaches corporations how to save money buying printing, brokers printing services, and teaches prepress techniques. Steven has been in the printing industry for thirty-three years working as a writer, editor, print buyer, photographer, graphic designer, art director, and production manager.]