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Glass and ceramic manufacturers have a variety of options to consider when deciding how to decorate ware to create a desired appearance. Decorators must consider design goals, production quantity, budget, product usage, desired ware longevity, inventory storage and other factors when deciding whether to use either direct screen printing techniques or decal transfer applications. There are no absolute rules that must be followed; however, experience and a basic understanding of decorating technology are critical.
Direct ScreeningScreening a decoration directly onto glass or ceramicware is the simplest option. It is ideal for basic shapes like cylindrical glass tumblers and ceramic mugs, and it is easier when fewer colors are used and there are few tight registrations, or points where colors meet. Direct screening is also ideal for extended print runs and when time and space limitations demand immediate firing of the ware after screening.
Substrate shape is a critical consideration when determining whether to use direct screen technology or decal transfer applications. It is generally more effective to use transfer technology to decorate surfaces with compound curves such as goblets; however, the screening process can be used to achieve certain designs on such ware. Also, when a decoration is too close to an obstruction, such as a mug handle, it is generally easier to use a decal that can be applied right up to the obstruction.
Although art glass decorators such as Glassmasters in Richmond, Va., have registered up to 20 colors when screening intricate designs on glass panels and similar surfaces, screen printing is generally more effective for less complicated designs. Tight registrations are more technically demanding on curved glass and ceramic surfaces than on flat surfaces, and failures are more easily noticeable on the finished product.
A decorator must also consider how quickly the ware is to be shipped when determining whether to screen or decal ware. If the ware is to be stored for a length of time, it would be economically sensible to print even a simple decoration on decal paper and apply as needed to maximize storage capacity. Some decal printers are also working to closely coordinate production with decorators to minimize storage requirements at decorator plants.
Numerous Society of Glass and Ceramic Decorators (SGCD) member companies produce screen printing equipment that is customized for a specific use within the glass and ceramic industries. From high-speed, multiple-color glass bottle decorators that can handle up to 125 glass containers per minute to basic, one-color ceramic mug decorators, equipment makers can provide a manufacturer with the necessary equipment to meet decorating requirements.*
The screening process can be fully automated with electronic color dispensers, lehr loaders, cross conveyors, storage conveyors, palletizers, depalletizers and other equipment to handle large ongoing decorating projects. Other custom screen printing equipment is available to efficiently print promotional mugs, tumblers or other ware. For small decorating runs, ware is generally loaded and unloaded by hand using relatively small units with printing quantities numbering in the hundreds of pieces or less.
Decorators can also use direct applications to apply precious metals, ultraviolet (UV)-cure colors, and specialty applications such as finely crushed glass. For example, the “Times Square 2000” mug (see Figure 1) decorated by The Allen Co., Blanchester, Ohio, was decorated using four iridescent inks in the first screening and finely crushed glass in the second screening to provide a special texture.
Direct UV-cure decorating options are available to decorate ware without firing. UV inks are generally used to decorate glass containers that have been previously sprayed with a ceramic coating or frosted, and this technique is typically used when durability is not critical. Several companies produce UV-cure systems, and research continues to enhance this process.
The screening process is heavily used in the glass bottle and tableware markets, where colorful but less intricate designs are generally popular. Decorators of promotional glass tumblers and ceramic mugs also use screen printing to apply basic logos or designs to ware quickly to meet urgent customer demands. In addition, some ceramic tableware is screened when basic patterns such as borders on flatware and hollowware are required.
Transfer TechnologyThe transfer decorating process is ideal when more intricate designs are applied to either glass or ceramicware. Instead of printing directly to a glass or ceramic substrate, an image is printed either by the decorator or by a decal printer to ceramic decal paper, and then applied to the ware. A skilled decal printer can achieve outstanding mass reproduction of just about any pattern using a great variety of colors. Decals are produced for over-glaze, in-glaze and on-glaze applications, and special effects including reactives, micas or interference colors can be applied.
Decal printers can readily achieve extremely tight registrations using as many colors as a design requires, as the printing process is conducted on a flat surface. Decal paper is much simpler to control while printing than bottles, mugs, tumblers or other glass or ceramic substrates, as it does not vary in dimension, roundness or surface texture. It should be noted, however, that decal paper should not be stored where large variations in humidity or temperature can affect its consistency, as the paper will curl and cause application difficulty.
Like direct screen decorators, decal makers can use the full range of unleaded ceramic colors to produce decals that will enable a tableware decorator to easily comply with heavy-metal leaching standards. Decal printers generally use four-color process or single color offset technology, although some decal printers are working with rotogravure and other technologies to reproduce near-photo-quality images for tile murals, collector plates and other ware.
Water-Slide Transfer TechnologyOnce a decorator has decided to use transfer technology, that decorator must determine whether to use a water-slide format or automated heat-release application technology. Water-slide applications are ideal for small-quantity decorating projects, where automated production would not be practical. In addition, water-slide decals can be used on almost any surface that can be direct-screened, and they are ideal when decorating around compound curves, over corners and through the loop of a handle. Many collectible decorators use the water-slide process to produce limited-edition collector plates and similar ware.
However, the water-slide process is labor-intensive, with decals applied by hand at rates in the neighborhood of 25 to 35 pieces per employee per hour for some types of ware. The application process itself requires skill. Water-slide decals are separated from their base paper through brief immersion in a water bath, and they are then applied by hand to the ware. Employees must carefully apply the decal without leaving air or water bubbles that will create defects when the ware is fired. In addition, ware must dry for about a day before firing.
Water-slide technology is used by glass as well as ceramic decorators. For example, Custom Deco South, Orlando, Fla., decorated 6,600 Masterpiece bourbon bottles for Jim Beam using water-slide decals to create a high-quality etched appearance (see Figure 2). The bourbon retails for $250 per bottle, and this enabled the distiller to budget accordingly to achieve a high-quality appearance, although the transfer process was much more cost-effective than actually etching each bottle.
Heat-Release Transfer TechnologyHeat-release decorating technology is ideal for large production runs, where speed is critical to produce ware cost-effectively. The technology is especially popular in the ceramic tableware industry, where both formal and casual patterns are produced efficiently in great volume. Heat-release decorating machinery is used to place a decal on the ware, and heat is then applied to separate the decal from its base paper. Unlike the water-slide process, ware decorated with heat-release decals need not be dried before firing. It is, however, difficult to decorate ware with varied compound curves using the heat-release process.
Heat-release technology is also used by companies in lieu of paper labeling to cost-effectively decorate glass containers, such as Gallo’s popular “Wild Vines” bottles, which are decorated using an Avery Dennison technology. The mass-produced bottles feature a unique multi-colored decoration with an etched appearance.
Advances in decal papers, transfer pads, decal printing and machinery continue to enhance the heat-release process. James Keegan, a pioneer in the development of heat-release decorating with The Pfaltzgraff Co., York, Pa., and now an independent consultant in Spring Hill, Fla., notes that advances in vacuum image application may enable heat-release decorators to work under handles, around curves and in hard-to-reach surfaces. He also questions the need for covercoat on heat-release decals.
Other Decorating OptionsGlass and ceramic decorators can create special effects using a wide array of decorating options. These options are often used to enhance the appearance of ware that has already been decorated using direct screen or transfer technology.
Decorative techniques including sandblasting, etching and frosting are used to enhance the appearance of glass containers, tableware and promotional products. Hand decorating is also an option when producing ceramic figurines, high-end tableware or similar products. This process is naturally labor-intensive, and skilled workers are required to produce the ware.
Pad printing is an alternative technology that is used to decorate glass and ceramic ware if screened decorations are not practical. In this process, the decorator engraves a plate with an image that is to be transferred. An enamel is then carried across the plate by a squeegee and followed by a sharp blade, which leaves only the enamel on the engraved plate. A silicone pad is then pushed against the engraved plate to pick up the image, which is then transferred to the substrate surface. Color selection, mediums, viscosity and ink surface tension are all critical elements to the pad printing process.
Increasingly, companies are striving to make photo-quality reproductions on ceramic substrates. The dye sublimation process has been improved dramatically in the past 10 years with tremendous color options available. The process is frequently used to economically reproduce photographs or other scenes on promotional mugs or souvenirs. Sublimation is not feasible on glassware, however, and the ware is susceptible to UV damage and image deterioration in the dishwashing process.
In the final analysis, a glass or ceramic manufacturer must decide based on experience how to decorate specific ware. It is important to work closely with decal printers and suppliers of colors, equipment and blankware early in the planning stages of a specific project to ensure maximum efficiency.