Although the decoration of ceramic and glass articles dates back over 10,000 years, recent changes in technology, government regulations, demand, and materials are transforming the industry. The proliferation of small batch wineries, microbreweries, distilleries, and other beverage companies has led to increased demand for customized beverage bottles, growlers, glassware, and even tap handles using ceramic and organic decorating materials, as well as precious metal preparations. Companies and consumers purchase customized decorated articles for promotional use or for special occasions. Production of specialized ware for theme parks, restaurants and other consumer brands also continues to grow.

The demand for ceramic tile has rebounded following the recovery of the U.S. housing industry. As major tile companies have moved to the production of larger-format porcelain tile, digital decoration is now being used by the majority of domestic tile producers. Meanwhile, consumer demand for artisan tile is increasing, with much of it decorated by hand.

Organic vs. Inorganic

Regulations such as the Consumer Product Safety Commission Reform Act of 2008 in the U.S., California Proposition 65, and REACH legislation in Europe have resulted in the decreased use of lead, cadmium, and other heavy metal oxides. This has led to the development and control of decorating colors containing less than 100 ppm of lead in the material. The restrictions in the use of lead, cadmium, and other oxides further limit the color space obtainable using ceramic decorating colors, which has also led to an increase in the use of organic decorating products by U.S. decorators and for those in countries supplying the U.S.

Ceramic decorating materials are typically composed of frits combined with ceramic pigments, and they are formulated to mature at the decorating temperatures needed for glass or ceramic products. They are applied directly or indirectly onto the surface of glazed ceramic or glass articles and fired at high temperatures. While glass enamels typically fire at 1,000-1,200°F, ceramic decorating colors fire at higher temperatures depending on whether they are onglaze or inglaze colors. Fired properly, these all form permanent glassy decorating colors.

Organic decorating colors vary in composition depending on whether they are two-pack systems, heat cured or UV cured. While the majority of organic decorating products are applied directly, some are also applied using waterslide decals, heat-release decals and reel-to-reel methods. Precious metal compounds, such as gold, platinum, and lusters, are also applied directly or indirectly onto glass and ceramic articles and then heat treated to mature and bond to the surface of the substrate.

The final properties needed by the customer tend to determine whether inorganic or organic decorating materials are suitable for use. Both types of products have advantages and disadvantages; decorators need to determine the suitability based on the final product characteristics or even regulatory compliance.

Ceramic decorating colors have better scratch resistance and chemical resistance than organic colors, but they have a limited color space and a need for heavy metals to achieve some colors. High temperatures are also needed to fire glass and ceramic decorating colors.

Organic decorating products allow for a wider range of colors to be produced and are cured at much lower temperatures than ceramic colors. While they may lack the scratch resistance of ceramic colors, the detergent resistance of organic colors can be suitable for many products. Organic colors also typically contain no heavy metals in their formulations.

Both organic and inorganic decorating colors can be applied directly onto glass and ceramic articles. Techniques include direct screen printing, spray, banding or brushing, pad printing, and total transfer.

In the U.S., the use and type of decorating products vary by industry. As domestic production of ceramicware has decreased, imported ware is also decorated in the U.S. using onglaze and inglaze decorating colors, as well as precious metal decorations. As the majority of glazes are now unleaded, decorating colors are available with less than 100 ppm of lead. While some leaded glazes and decorating materials are still in use, all decorated ceramicware and glassware must comply with current regulations for lead release or content.

Unleaded and organic decorations continue to increase in usage by ceramic and glass decorators. Even precious metal decorations are now possible using inkjet and organic systems. Organic decorating materials are also applied directly or indirectly onto the surface of glass and ceramic articles and heat treated at low temperatures or cured by exposure to UV lighting.

While primarily developed to color clear glass, forehearth colors are now being used to decorate ware using different techniques in production. Potential effects include streaks, bubbles, fluorescence and snow.

Organic decoration has gained a major share in the decoration of glass and ceramic articles. Direct-print inks can be applied by screen print directly onto the substrates and then heat treated at low temperatures or UV cured. Waterborne coatings are sprayed onto pieces and then heat treated to mimic colored glass.

The direct printing of UV-cured and thermoplastic decorating colors allows for multi-color decorations onto glass surfaces. Waterslide organic decals have been developed with improved scratch and detergent resistance, although they currently need to be applied by hand. Heat transfer technology allows for direct application of organic decals onto glass, ceramic, and even some plastic articles using high-speed digital transfer technology and equipment.

Dye sublimation has also increased in use for the decoration of ceramic substrates. Images are printed using special inks onto sublimation paper. The decals are applied using heat-resistant tape, and then heat treated for adhesion to the substrate.

Direct screen printing of glass enamels continues to be the dominant decorating technique for architectural and automotive glass. Direct inkjet application of glass enamels onto architectural glass has seen some limited use, however. Appliances continue to use ceramic decorating materials for glass and areas needing heat resistance. Organic inks, however, are now the primary method used for decoration by the appliance industry, even onto porcelain enameled surfaces.

Over the past 15 years, the U.S. tile industry has seen a swift transformation from screen and roller printing to ink-jet technology of ceramic decorating colors by high-volume producers. Digital inkjet printing has become the standard decoration technique for all major U.S. ceramic tile producers, as well as most major tile-producing countries. Over 70% of tile in the U.S. is produced using ink-jet technology.

At the same time, the number of smaller artisan tile producers continues to grow. While some are using new decorating technologies, many are screen printing or hand brushing the decorating colors. Due to the durability needed for ceramic tile, the use of organic decorating products is very limited.

Recent Developments

Equipment producers have developed digital inkjet printers that can decorate 3-D objects with UV-cured and thermoplastic inks. These allow for four-color printing, as well as additional spot colors.

Several companies have introduced direct digital inkjet printing of ceramic decorations onto dinnerware. While currently limited to flatware, the inks are applied directly onto unfired glaze and fired at normal glaze firing temperatures.

Laser marking materials have been developed for glass and ceramic substrates. Materials are applied by spray, brush, or screen printed and then heat cured using carbon dioxide (CO2) or fiber lasers to produce permanent marks on the surface. This method enables the personalization, customization and sequencing of individual articles.

Ceramic waterslide decals can be produced using laser-jet toners that contain ceramic decorating colors. This method is a good option when custom decals need to be produced in limited quantities or for the development of prototypes.

Going forward, digital printing technology will continue to gain in popularity for both organic and inorganic decorating products. In addition, the use of leaded products will continue to decrease, along with some decorating colors, due to regulations in the U.S. and abroad.

For additional information, contact the author at todd.barson@ferro.com or visit www.ferro.com.