ABSTRACT

Sublimation is a chemical term that is used to describe a specific method of printing. For many years this process has been used to imprint all types of fabric articles ranging from clothing to pillowcases. Until recently, equipment and preproduction costs limited this technology to use in high-volume manufacturing.

The advent of new photo processing equipment and supplies brought the technology into the personalized products industry. The most common items produced using sublimation technology are t-shirts and mugs. In a marketplace where consumers constantly demand new products, many other personalized gifts are coming on steam.

Personalized jewelry items are one of the latest products to fill consumer demand. This paper will explore methods by which photographic and/or computer-graphic images can be applied to metal substrates used for jewelry production, and other products.

THE SUBLIMATION PROCESS

Sublimation printing is a process that uses special ink applied by an inkjet printer onto a photo paper. Unlike in other decorative transfer methods, this image is then heat transferred into the substrate’s surface.

Sublimation printing first became popular as a way to color and decorate many products, from fabric for sports uniforms to shoelaces. One of the first products that I had experience with was woven fabric material used for children’s belts. Some belts were decorated with popular designs such as flowers or camouflage patterns, while others were decorated with licensed characters such as Spiderman and Ninjas. The advantage of this type of printing, though a little more expensive per piece, is that it could be set up quickly with limited change over expenses. The drawback to this process was that the images were only available from special offset printers, with all the associated production expenses.

Recent advances for producing digital imagery, user-friendly coatings and innovative substrates have made sublimation a viable and cost effective means for making small to medium production runs and individual personalized products such as jewelry.

THE CHEMISTRY OF SUBLIMATION

The physical properties of matter follow the general rule of phases: it will be in the solid stage at its lower range of temperature, the transform into a liquid as the temperature is raised and then change into a gas at its high-temperature range. The typical example of this is H2O which changes from solid-phase ice to liquid-phase water to the gaseous phase of steam.

Webster’s Dictionary defines sublimation as, “to pass directly from the solid to the vapor state.” That is to say that the compound has the special ability to skip a phase. For example, CO2 as dry ice changes from a solid directly to a gas as you elevate the temperature.

There are several forms of sublimation printing. Dye sublimation printing is the form that we will refer to throughout this paper. In this method of printing, heat is applied to a solid dye, transforming it directly to a gas. The dye is then transferred to the substrate, using pressure and heat.

SUBSTRATES

Substrates are the base to which the images are applied. The substrate materials are limited only by their ability to accept a coating and maintain their mechanical properties and color fastness at the temperature used in the process. Materials must be able to withstand temperature ranges of 300-400f. Typical substrates include polyester-based cloth materials, ceramics, porcelain, most wrought metals and metals that are cast above 400f alloy melting points. Plastic blends that can maintain their integrity at 300-400f, such as FRP, nylons and some thermo-set plastics can also be used for sublimating.

COATINGS, INKS AND PAPER

For a substrate to accept a color image with any degree of quality, the surface must be coated with a polymer specially designed for the particular application. The key to a superior product is the coating. Dye penetration of this surface is necessary to replicate the vibrant colors and to keep the dye from rubbing off the surface. The color and reflectivity of the substrate and its ability to form a good bond with the coating is another factor in creating a vibrant and durable image. Paper and inks are specially formulated for this type of printing process. The inks and paper combination must be so as to have an even release during the heat and pressure stage of sublimation. Normally, the imaging process uses the standard CMYK printing system, although newer developments allow the use of five – or six- color printing as well.

JEWELRY PRODUCTS

Quality jewelry featuring personalized photos is increasing in popularity and there is now far greater consumer demand for these products. This is partly die to advances in digital imagery and user-friendly products. Subliminationn technology provides the ability to utilize customer logos, artwork or individual photographs to create on-of-a-kind, full-color products. Gold, sterling silver or base metal substances can bring these personalized items into any price level of jewelry marketing. Products such as pendants, earring and bracelets can ne personalized with full-color photos. The process also lends itself to imprinting on items like jewelry boxes, keychains and pill boxes.

THE PRODUCTION PROCESS

The first step is deciding the type of item to be produced and what subject matter is to be sublimated into it. There are a variety of substrates currently available tat will accept sublimation printing, but special items can be manufactured from scratch as well. To illustrate the process, I chose a simple blank of pre-coated sublimatable aluminum. The size and geometry of the blank must be gauged.

Next, select a photograph that is appropriate for the geometry and size of the aluminum blank. it must be noted that the most vivid color photograph will produce the most spectacular piece of jewelry. The size of the image to be transferred is important because it will be reduced dramatically in order to fit onto a relatively small piece of metal. If a photograph or other type of image is to be used, it must be scanned first. Digital images can be used directly. All the basic rules of image production apply to this step, just as it would in any form of graphic art. The image must be cropped and sized so it will fit onto the substrate blank with some bleed.

The next step is to import the scanned image into your desktop computer. Any graphics program can be used to make final color or image changes. The PC must be specially set up with a color adjustment program, which is usually supplied by the ink manufacturer. The printer must be loaded with special sublimation cartridges and transfer paper. Filter the image on the computer with the color correction software and print the image onto the special paper. The image look muted and reversed. The ink colors are not vivid on the transfer paper. The colors will only come alive once the image has been printed.

The next step is to sublimation print onto the jewelry finding, in this case an aluminum blank. The image that was printed on paper must now be overlaid onto the metal substrate and placed into a heat press. The heat press is usually set a temperature between 350-400°F with a standard clamping pressure. The press is then closed over the part, with a dwell time of about one minute, at which time the press is raised and the part removed. The image paper is then removed from the blank and the result is an indelible photo-quality color image sublimated into the surface of your jewelry piece.

DRAWBACKS AND RESTRICTIONS

Despite the fact that sublimation printing has advanced a great deal and been simplified to the point that it is an extremely user-friendly process, there are restrictions and inherent problems as with any form of decorating. Best results are achieved when flat substrate objects, or slightly domed ones, are used. Odd-shaped jewelry findings will require special adjustments to the heat press, which may often be difficult to achieve.

Color matching can be another inherent problem. The images are generated on a computer screen in an RGB format and then transferred onto special paper in a CMYK format. The true color tone of the image on the final piece is not visible until the part has been completed. This eliminates the ability to fine tune the image coloration. Exact color matches are extremely difficult to achieve using the sublimation process.

Another drawback worth mentioning, though it is not always important for jewelry items, is that the coatings that have been developed to-date are susceptible to UV degradation. Continuous exposure to sunlight will fade the image slightly over long periods of time.

OTHER PRODUCTS

There are scores of other products in the marketplace that lend themselves to the sublimation process for personalization. Goods available in the home furnishings industry and the awards and recognition field are good examples. Signs, name tags, decorative tiles, drinking mugs, mouse pads and many other items are suitable for sublimation printing. The sublimation process for consumer goods is limited only by the imagination of innovative manufacturers, and the market is always eager to accept new products.

ACKNOWLEDGEMENTS

Universal Woods, Louisville, KY