Over the past few years, inkjet has emerged as a viable option for decorating architectural glass, though screen printing is still used in this specialized market. See how both processes have been employed in innovative projects from around the world.
By Wim Zoomer
Just a couple years ago, screen printing was the only method used to decorate flat glass for architectural purposes. One reason screen printing monopolized this market is its versatility. It can be used for both printing (selectively imaging designs) and coating (complete solid coverage). It also allows for an almost limitless range of deposit thicknesses depending on the ink and requirements of the job.
Screen printing also had the unique ability to print ceramic pastes with glass frits and deliver the tough physical properties this application demands. The final performance of the graphic depends upon the ink system the printer selects and the post-print treatment the ink requires. In order to achieve long-term weatherability and light fastness, printers commonly use ceramic pastes, which are fused into the glass at temperatures of approximately 1300°F after printing. Once exposed outdoors, glass printed with ceramic pastes won’t be affected by the climate, even when printed on the first (outside) surface. Other options for glass that don’t provide the same permanence include solvent-based sol-gel inks (which are temperature treated at 392°F) and UV inks (which cure by polymerization).
One disadvantage of screen printing is that every image requires a corresponding screen. Manufacturing these screens involves relatively high expenses for labor (coating, exposing, and developing the stencil) and materials (including frames, chemicals, and screen mesh). Glass printing also demands a relatively large, dust-free area to process and store the screens.
Screen printing remains a cost-effective technique for decorating flat glass for architectural applications, especially when the job entails decorating a number of panes with the same design or selected parts of the image. But, just as it has in other segments of the printing industry, inkjet is carving a role in flat glass decoration. Inkjet presses can be operated by a single person and they eliminate the prepress expense
of screen printing, making the technology cost-effective.
It’s ideal for sampling, manufacturing one-offs, producing short runs, and handling jobs where graphics will be customized or changed slightly from one panel to the next.
The drop-on-demand printhead technology allows substrates to be printed edge to edge, and, as the technology has evolved, the systems have gained in throughput speed to the point that jobs involving a few hundred panes of glass may still fall below the breakeven point at which screen printing would be more economical.
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