October 23, 2015
By Brian Savage
As the demand for new and different design elements in the Canadian construction market continues to grow, digital printing on architectural glass is one element that can be ideal for adding a distinctive touch to projects. Multiple colours, versatility, and potential cost savings are just a few of the benefits available with this process.
Digital printing lends itself well to both interior designs and exterior façades for both functional purposes as well as artistic purposes. In fact, more than 50 Canadian municipalities have public arts programs and policies in place, and there have been multiple projects sponsored by these programs that integrate digital imaging into their final design.
Previously, when architects wanted to add printed design elements to the glass skin or the interior of a building, they were limited to processes like one or two-colour silk-screening or digital prints with difficult-to-use and organic-based inks. Ceramic-based inks have now transformed digital printing, resulting in a much more controllable process with a durable, long-lasting, and colourful print. The current generation of digital printers gives the designer the opportunity to turn what was once just the functional façade of a building into a decorative canvas. The use of digital printing also provides the opportunity to optimize design, colour, and solar performance for façades.
For example, the new Centre hospitalier de l’université de Montréal (CannonDesign) will have 13 works of public art incorporated into the final design. The largest of these is a 2610-m2 (28,100-sf) digital print designed by artists Simon Rivest and Mathieu Doyon, made of up five mountains spanning eight floors formed by digitally printing approximately 15,000 individual starburst-shaped elements in multiple colours.
One of the largest public arts installations ever in the city of Montréal, Rivest and Doyon worked closely with the glazing subcontractor (Gamma) and glass fabricator to ensure their vision and design intent was met while still providing the high-performance glazing required on this project—dual-insulating and triple-insulating glass with the digital printing and a low-emissivity (low-e) coating both on Surface #2.
The basics of digital printing
There are differing types of digital printing processes available for the architectural glass market, with the two main differences being the types of ink used and how the machine transfers it onto the glass substrate. This article focuses mainly on inkjet-style printers that use drop-on-demand technology.
Inkjet-style printers utilize a programmable print head that travels back and forth just above the substrate where the image is being applied. Each colour of ink has its own grouping of nozzles on the print head that are individually activated and drop the ink onto the glass substrate in the proper location—hence the name ‘drop on demand.’
Most digital printers specializing in architectural glass are capable of printing in resolutions up to 720 dots per inch (dpi). There is generally a per-square-metre upcharge for digital printing over and above the per-square-metre charge for a glass unit. Additionally, there may be added fees if further work is performed by the glass fabricator, such as prepress adjustments to the electronic design file. Understanding the fabricator’s requirements and capabilities early in the design process can help minimize these added fees.
The flexibility of digital printing means it can be used monolithically or included in laminated and insulating glass (IG) units. It can also be used in combination with interlayers and have solar control coatings applied directly over the digital print resulting in improved solar performance. Digitally printed glass can be used in many different areas of a building, including exterior façades, interior dividing walls, signage, and office walls.
With the use of specialized Surface #1 inks, digital printing can be applied to the exterior of a piece of glass. Some areas where Surface #1 inks can be useful are in bird-friendly applications or adding an element of depth to a building. However, these inks are limited in colour to black, white, and grey hues, which may limit design flexibility.
The versatility and resolution capability of ceramic ink means many different types of images can be printed, including photorealistic images, text, variable graphics, and patterns. Additionally, visual textures similar to wood grain, granite, and marble can be produced with excellent results. Both the transparency and opacity of the print are also controllable.
Digitally printed glass can be cleaned and cared for in the same manner that other ceramic frit coated glass is maintained. As a general rule, if it harms the glass, it will harm the print. However, in most applications, it will be permanently protected in an insulating or laminated unit.
A striking example can be found with the approximately 18-m (60-ft) tall El Paso Clock Tower (designed by Populous) at Southwest University Park. The colourful artistic glass window depicts more than 800 years of the Texan city’s diverse history. Artist Roberto Davidoff’s creation, with work by glazing contractor Signature Architectural Elements, includes many vivid colours digitally printed on the monolithic and laminated glass’s Surface #2. The piece is viewable from both the exterior of the stadium and from the staircase within the clock tower. A clock-face was also printed on Surface #2 and then fabricated into a laminated unit to complete the installation.
Comparison to other glass enhancements
In the past, when there was a desire to add a visual design element to a building’s façade or interior, architects have by and large been limited to a narrow range of products and methods, including silk-screened designs and various interlayer systems. Each has its advantages and disadvantages.
Silk-screening is usually most cost-effective when there is a desire for just one or two hues, a repeating pattern is used, and there are many units to be silk-screened. However, the actual screen used in the silk-screening process can be cost-prohibitive and it is limited in the number of prints it can produce before it reaches the end of its useful life. Printed and coloured interlayers can be useful when solid colours are required, but they can only be employed in laminated makeups.
Characteristics of ceramic ink
The inks in digital printing are very similar in nature to the frit used in the silk-screening process. Both frits and inks are ceramic-based; they perform and behave almost identically to each other. The main difference is the latter is produced with smaller particles of glass to allow the inks to flow through the print head onto the glass substrate. The inks also contain inorganic pigments, which help them to be as colour-stable as ceramic frit over the life of the printed image.
Although the ceramic inks are durable and resistant to scratches and weather, care must be taken to protect the image from damage, especially when it is exposed (e.g. on a monolithic piece of glass). With proper maintenance and protection, the printed image should be expected to last the unit’s lifetime.
The inks used in Canada and the United States contain no heavy metals such as cadmium or lead—consequently, some brighter pinks, reds, and purples may be difficult to achieve. Even with that limitation, a wide gamut of colours can be attained by mixing the base ink colours into final printed colours. All of the colours will have similar ultraviolet (UV) fading resistance.
The inks are also able to be applied by the printer at varying thicknesses to achieve design results like solar control or desired colour variations. For example, blue ink tends to be more translucent than other colours, so a print with more blue in it may allow more light transmission to the interior of the building during the day. A design incorporating more blue than other colours may also let out more light at night as viewed from the exterior of the building.
Since digital printing is so versatile with regard to colour selection, ink opacities, and design choices, the calculating of performance data can become quite complicated, especially when the print is artwork versus a dot or line pattern. Artwork can involve multiple colours and ink opacities in random layouts, potentially making performance data variable across the image. If specific performance requirements are specified, the designer and architect should work with the glass fabricator as early in the design process as possible to achieve the desired performance metrics.
If the intent is to limit the transfer of light, the various colours can be applied at different opacities to balance the amount of light transferred. However, the reverse is also true. If the intent is to create a façade that essentially glows with a stained glass effect from the interior or exterior, the image can be adjusted to achieve the desired outcome. Viewing small-scale sample and large-scale mockups of the print in the final makeup at the target location and environment for an accurate representation of how the colours will actually appear is recommended.
The digital print process
The actual digital printing procedure can be separated into two distinct but dependent processes—electronic design file manipulation and printing the actual image on the glass substrate.
The electronic design files can be produced in many different formats. Raster and vector-based images are both acceptable in this process, but the latter are printable at any size without resolution loss, so they tend to be preferred. Proper preparation of the image files is one of the most critical steps in the entire process. The quality of the printed glass can only be as good as the file used to generate the print.
The design files can be individually designed for each unit to be produced, or the entire elevation can be designed as one file and the software can tile the image across the façade. The glass fabricator’s software can also adjust the image for the inclusion of items such as mullions and holes for point-supported glass so the image flows seamlessly from one pane to the next. Finally, the software rips the image into a final digital file that will be used at the production stage.
These electronic files are then sent to the printer where the image is interpreted and the ink is deposited onto the glass substrate. Once the lite of glass has the image printed on it, it is sent through an infrared tack oven to dry the ink. At this point in the process, the ink has a matte finish and has not permanently adhered to the glass substrate. The printed image is sent from the tack oven through a tempering oven where it must be either heat-strengthened or fully tempered to permanently fire the ceramic ink to the glass.
It is only after being permanently fired to the glass that the ink takes on a glossy finish. From here, the printed glass can be directed to other processes, including having a coating applied, laminating, and insulating lines. If it is to be used in interior applications, it might even be left in monolithic form.
Benefits and limitations
There are many benefits that come with the digital printing process. A few of the most frequently cited are cost savings, design flexibility, and repeatability. The cost savings over silk-screening occur when there are a large number of screens required relative to the final number of units that need to be produced. There are also no storage costs with digital printing that are usually associated with screens, as the files are stored electronically.
Design flexibility is achieved by allowing for custom images consisting of multiple colours. Micro-lines, micro-dots, and dual images add to the flexibility offered by digital printing. Dual images consist of an image viewed from one side of the glass with a different image viewed from the other side of the glass, even though both images are printed on the same surface of the glass. Finally, since the design files are stored electronically, replacements and reproductions can be produced months and even years later with dependable results.
However, if the print is exposed to UV light, it may fade over time. This makes precisely matching replacements more challenging. Colour adjustments may need to be made to the electronic art file before printing to ensure a satisfactory replacement.
There are also limitations to the digital printing process that must be taken into consideration to determine if digital printing is the appropriate choice for the project. Calculating performance data across the façade can prove to be challenging. As mentioned, the various colours of ink can transmit light and solar energy at different levels. However, minimum performance levels can be calculated because the performance characteristics of the glass substrate, any coatings applied to the digital print or glass substrate, and other enhancements are already known.
Matching the colour of the final printed image to the vision of the architect or designer can also pose a challenge. The amount of light being transmitted and reflected during a sunny versus cloudy day, time of day, and interior lamp colour temperatures and lumens, all affect the way the image is perceived at different times.
Additionally, applying a coating over the print may slightly alter the vibrancy of the colours. The choice of substrate can also cause the colours to appear different than the design. For example, regular clear glass may impart a green hue to the image while a low-iron glass substrate helps subdue the green shift effect. As each printed image is different in terms of colour, design intent, and the way the image is constructed within the designer’s software, the adjustments necessary to compensate for coating and substrate choices will be different for each printed image. All these issues must be taken into account when designing an image using digital printing.
Designed by Toronto-based Ziedler Partnership Architects and Snøhetta (Olso), Ryerson University’s 5000-m2 (53,820-sf) Student Learning Centre utilized more than 3000 digital printed glass panels, covering 60 per cent of the building. Digital printing on the façade (shown on this magazine’s cover) helped contribute to the building being designated as LEED-certified under the Leadership in Energy and Environmental Design rating program, with Silver currently pending.
Digital printing contributes to the Energy and Atmosphere (EA) category by helping achieve the Minimum Energy Performance credit through a contribution to a reduction in the glass’ solar heat gain co-efficient (SHGC). Further, digital printing can contribute to the Innovation in Design (ID) category though the pilot credit, Bird Collision Deterrence.
In the case of the Ryerson building, the design was intended to meet high energy efficiency while maintaining the use of natural light. The combination of digital ceramic in-glass printing with a triple-glazed construction and low-e glass coating help to achieve the required functionality that included thermal comfort, glare control, bird safety, and sun/shade control. The glass makeup for the project, with Flynn as glazing subcontractor, included triple-insulating glass with digital printing on Surface #2 and the low-e coating on Surface #4.
There is a constant demand for new and diverse ways for architects and designers to express their client’s design intent on the façade of the buildings they are designing. Digital printing has emerged as a versatile and colourful addition to the supply of products that help to define this vision. Not only can multiple colours and design concepts be added with relative ease, but many performance aspects within the design of the façade—such as solar control and privacy—can also be fine-tuned through both settings on the printer itself and via available software features.
Digital printing is versatile enough to be used in interior and exterior applications, can be employed in combination with other architectural glass products, and has the durability of ceramic frit applications that have been utilized for years in architectural design. As more projects in Canada incorporate digital printing and prove the artistic and performance benefits, now is the time to become aware of the technology’s capabilities on building projects.
Brian Savage is a product manager with Viracon. He is a LEED Green Associate and has worked in the construction industry for 12 years. Savage has helped launch numerous new glass-related products at Viracon. He can be reached via e-mail at firstname.lastname@example.org.
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