High-quality, continuous-tone decals can be printed easily and quickly using a new digital printing technology.

The beauty of a ceramic piece is a complex interplay of form, color, texture and surface decoration. One type of surface decoration is the decal or transfer, which is traditionally produced through direct screen printing. However, direct screen-printed decals require relatively large, expensive equipment and substantial floor space, and dryers and solvents place heavy energy and environmental demands on the printer. Additionally, long production runs are generally required to distribute the cost of color separations, sizing, screens, changeovers and other processes over a large number of decals.

Today, with new ceramic toners and commercially available digital technology, high-quality, continuous-tone decals can be printed easily and quickly. Short runs and even one-offs are economically possible. Using digital decals, custom-decorated products, prototypes and personalized ware can be manufactured at a reasonable cost.

Using Ceramic Toners

The key breakthrough in digital decals was the development of ceramic toners designed to work in commercially available laser copiers and printers. These toners are being produced in Germany through a patented process in which selected ceramic colors-i.e., a flux and ceramic pigment mixtures-are melt-mixed in a suitable resin. During the mixing process, the organic material surrounds the ceramic color. When cooled, the solidified resin and color mixture is pulverized and graded to yield the properly sized colored particle or toner.

Digital ceramic decals are printed using a four-color process-cyan, magenta, yellow and black (CMYK). To achieve good color management on ceramics, the four selected colors must be of the proper color strength, tone and refractoriness so that they work well both individually and in combination. This allows the widest possible color gamut (color space) while ensuring that the mixture color is consistent and reproducible. For the color green, for example, the yellow and blue (cyan) must be of the same refractoriness and the proper color strength and tone to yield a wide gradation of green shades and hues. The green must vary predictably with the total amount of color printed and with the relative amounts of blue and yellow deposits making up the final color. The new toners were specifically created to achieve these properties.

The new ceramic toner system meets the vast majority of printing requirements, including portraits and landscapes. Recently, a selenium-based palette was also added to the color mix. The modified four-color system produces a somewhat different color range, including true red and orange hues. With the properly engineered cover coat systems, the ceramic toners meet even the stringent requirements of California's Proposition 65.

Creating a Digital Decal

To create a digital ceramic decal, the film, artwork, print or photo is first scanned directly into a computer. A digital camera can also be used to provide the image. Regardless of the source, the image must contain enough optical data to print with 300 dots per inch (dpi) of "real" information. This means that an image scanned at 600 dpi optically can be enlarged two times and still have great detail. If a digital camera is used, a three- or four-megapixel unit typically provides enough resolution for a 5 x 7 in. image.

Since the image files are rather large, the user should have a fast PC or Mac with a large amount of memory and a high-quality monitor designed for graphic work. Software for image manipulation and desktop publishing is also required.

After image adjustments are complete and the decal sheet has been previewed on the computer monitor, the data is sent to a color server, which manages a laser printer. A relatively high-end copier and printer, such as the Canon 900, is recommended to produce digital decals. When used as a copier, the machine can print decals directly from images placed on the glass. When used as a printer, the color server manages the data and the printing process, freeing the PC or Mac for other tasks.

With ceramic toners in place and water slide decal paper in the carriage, printing begins. A3 (11 x 17 in.) paper is currently the largest size that can be used to print digital decals.

After printing, a cover coat is applied to the decal paper to protect the printed image and to allow the print to be transferred to the ware. The cover coat, which can include an optional flux, can be applied using special heat release cover coat sheets. The sheets are placed on the print and are run through a laminator to transfer the cover coat to the print. The cover coat can also be applied by conventional wet screening over the decal sheet. If necessary, a screen can be made to cover coat only the actual image.

Once the cover coat is in place, the water slide decal is ready to be applied to the ware and fired. The ceramic toners are designed to be fired on glaze at 800C, enabling them to be used on fine ceramics. The 800C firing also allows digital decals to be used as surface decoration on porcelain enamel and borosilicate glass. The entire printing and coating process typically requires only one to two minutes to complete.

The Digital Advantage

Digital ceramic decals offer a number of advantages to decal producers and ceramic decorators. The process is fast, and short runs are possible at a relatively low cost. A scanned image is manipulated on the computer; a decal is printed, applied and fired; and the final result is available for review on the actual ware within several hours. Runs as short as one decal or as long as several thousand decals are possible, and since the image data is stored on a CD, a run of one or more of the exact same print is possible the following week or the following year.

Samples or prototypes can be quickly produced and presented to buyers, focus groups or management. Adjustments to the color, size or overall image can be easily made, and corrections are just a click away. Additionally, the images achieved by the 300 dpi printing are near photographic quality. For comparison, a typical TV monitor displays at about 72 dpi (or pixels per inch), and a typical magazine picture is printed at about 266 dpi.

Production space requirements for digital ceramic decals are also minimal. A 12 x 12 room can easily contain the scanner, computer, server, copier/printer and laminator, thus becoming a mini-factory. Approximately 1400 A3 sheets can be printed in an eight-hour shift (at 3.5 pages per minute). Since six wall tile-sized images will fit on a single sheet and since each image can be different, up to 1400 decals of each motif, or 8400 total decals, could be printed for decorative tiles. Depending on the image size and coloration, a single set of toners will print 4000 to 6000 A3 sheets. An office-sized space can typically be fully equipped with purchased and/or leased equipment for less than $20,000. For companies that prefer not to invest in their own equipment, digital decals can be obtained from some decal producers.

Future Improvements

Digital ceramic printing is in its infancy. Due to current limitations in technology, digital decals are limited to 11 x 17 or smaller images and can only be used as on-glaze decorations on ceramic and porcelain enamel products. However, research and development efforts are ongoing. New and modified fluxing materials will enable the development of toners for glass, as well as in-glaze and under-glaze decoration. Printers will be faster and will be capable of producing larger formats with up to eight colors. Engineering work is also under way to make digital printing with ceramic toners an in-line process, making it more cost-effective for extremely large production runs.

As digital printing develops and adjusts to the specific needs of the ceramic industry, the cost reductions and increases in speed, flexibility and quality enjoyed by others in the printing industry will also become available to the decal producer and decorator.

Editor's Note

The patented digital decal technology discussed in this article was developed in Germany by Michael Zimmer, who also manufactures the ceramic toners, and is being marketed and distributed worldwide by Digital Ceramic Systems, a partnership between Zimmer and Stuart Jones, located in the UK. The technology is available in the U.S. through licensing agreements from Design Point Decal, Inc. and Urban Clay Inc. For more information, contact: John Gayle, Design Point Decal, Inc., 10 Midland Ave., Port Chester, NY 10580; (914) 935-3300; fax (914) 935-3310; e-mail info@designpoint.com; http://www.designpoint.com; or Dennis Caffrey, Urban Clay Inc., 2424 E. 55th St., Los Angeles, CA 90058; (323) 581-8702; fax (323) 581-0198; http://www.urbanclay.com.

SIDEBAR: Award-Winning Technology

Decal producers are already experiencing a great deal of success with digital ceramic decals. Design Point Decal, Inc., one of the first companies to embrace the new technology, won a Discovery Award for Technical Excellence at the Society of Glass & Ceramic Decorators' DECO 2002 show in Arlington, Va., for this highly detailed four-color design titled "Tea Time." The design was produced using the digital decal process.

Design Point Decal supplies both conventional screen-printed and digitally printed decals, and also supplies the new digital decal printing technology to companies interested in producing their own digital decals in-house. For more information, contact the company at (914) 935-3300, fax (914) 935-3310, e-mail info@designpoint.com or visit http://www.designpoint.com.