Artisanry, Architecture, and North American Glass Tile  

A boundless spirit of innovation, a passion for hot glass, and a new vision for the tile industry has marked the recent emergence of handcrafted glass tile manufacturing on the West Coast of the United States. The benefits of this relatively new scene extend to architectural design and interiors as well as specialty applications, such as swimming pools, water features, and sitework. For architects, the challenge today is how to best capitalize on this artisan heritage to create colorful, timeless, and highly durable designs and ensure proper, lasting installations, while also using a recycled and environmentally friendly material: old bottles and waste glass.

Photo courtesy of Oceanside Glasstile/Robert Thien

Mosaic tile is one of the world’s oldest forms of finishes, yet it is sophisticated, highly durable, and sustainable today.

As with any building material, however, issues can arise in working with architectural glass tile, whether mosaic or larger-format tiles. The two most critical are the quality of the manufacturing processes as well as the suitability of application specifications and installation techniques. A wide range in quality separates the producers. In fact, the boom in glass tile products over recent years goes beyond the artisanal makers and West Coast companies. A proliferation of manufacturers worldwide and the emergence of varied production techniques have made the specifier-designer’s task even more complex. “It is very important to select the correct product for the installation application,” says Johnny Marckx, an executive vice president of one North American maker. “The architect’s project team should be familiar with manufacturing and quality standards, tile mounting methods, and other installation techniques. It is also important to review the impact of glass tile on project sustainability.”

Before arriving on the jobsite, glass tile is produced and sourced in a number of ways. Architects experienced in glass tile use typically design with awareness that not all of these products are created equal. Some brand names have invested millions of dollars into quality control standards, product testing, installation technique support, and education. Other companies may make glass tile products in ways that hold up less than adequately in common application environments.

To become reasonably expert in glass tile design and specification, it also helps to know enough about the key ingredients of glass tile, how various products are made, and even some history about glass tile. In addition to reviewing key manufacturing methods, design professionals should be familiar with glass tile testing protocols and installation standards. These provide guidance and help ensure successful buildings, landscapes, and interiors made with glass tile. The three key groups to reference are the American National Standards Institute (ANSI), ASTM International, and the Tile Council of North America (TCNA), which publishes its widely referenced TCNA Handbook for Ceramic, Glass, and Stone Tile Installation.

Photo courtesy of Oceanside Glasstile/Jeff Glasener

Properly specified and manufactured glass tile surfaces are resilient and durable, offering a sustainable luxury finish using recycled bottle glass.

History and Invention

The attraction of glass tile seems self-evident to many. “The colorful, intricate patterns of mosaic and the luster of large glass surfaces offer an authentic, gratifying experience that serves human values, positive vibrations, and cultural vision,” says Marckx, an expert in the industry. Glass tile surfaces are resilient and durable, offering a lasting protective finish with a good return on investment (ROI). For the green-minded owner or designer, creating a luxury finish using recycled bottle glass is an impressive double win.

It’s also a longtime favorite. Glass tile is one of the oldest mediums for creating color in murals, according to William Ellis in his authoritative book, Glass.1¹

Although it is perceived as relatively new and part of the modern architectural lexicon, glass tile has been used in murals dating back to 2500 BCE, around the same time the Giza pyramid complex arose in what is now El Giza, Egypt. Mosaics with glass tile first appeared in the Hellenistic period, adding unlimited color possibilities, according to Frederick O. Waage: “With the development of wall mosaic, glass largely took over the functions of stone, producing tints of unsurpassed intensity and leading to a continuing search for new coloristic effects.”²

Then and through the modern era, glass tile is generally composed of three primary ingredients: silica sand, fluxes, and metallic oxides, according to the Corning Museum of Glass. Silica, a perpetual resource and the major ingredient in glass, forms a transparent, brittle substance when properly heated and mixed with other components. (Lightning strikes have been known to fuse blobs of impure glass from beach sands.) Added to the process are fluxes—including alkalis, such as sodium carbonate (soda) and potassium carbonate (potash)—to lower the melting temperature and help keep heating consistent throughout the process. Fluxes also help release impurities in the process. Last, manufacturers introduce metallic oxides to create color in a through-body glass tile. Different metals fire off of each other at different temperatures, which creates a byproduct of color.³

As with any liquefied product, the resulting molten glass material can then be molded and formed. It can be paired with natural stone and porcelain, among other materials, as it was in the earliest mosaic applications. Using various techniques, finish types can be applied today, such as non-iridescent, iridescent, and matte finishes. Three broad categories of glass tile manufacture create the range of products available for architectural and landscape uses: cold, warm, and hot.

Cold

The first manufacturing method, cold refers to low-temperature glass, which employs a sheet glass (not unlike common float glass window panels) with coatings added onto the back of the tile at temperatures lower than about 1,000 degrees Fahrenheit. The resulting sheets of backpainted windowpane glass are then cut and finished as needed. One benefit of this production method is that it allows for a broad range of colors, including Pantone Matching System (PMS) colors. However, while many colors are achievable, the cold glass tiles have limited applications. They are generally only suitable for indoor walls because the paints and coatings are not fully bonded to the glass material. For outdoor and other wet applications, the low-temperature applied paint can delaminate and chip under typical atmospheric conditions. In addition, the cold products are often mounted with a mesh, which may be visible in certain installations or when craftsmanship is poor.

Warm

The other general type of glass tile is warm. This refers to several types of manufacturing methods, and each can produce a range of unique visual and tactile effects, all produced at a range of temperatures from about 1,023 degrees Fahrenheit to 1,599 degrees Fahrenheit.

Fused

Named for the fusing of color onto float glass and the fusing together of glass panels, this method involves cutting glass into sections and shapes, followed by firing in a furnace. Color is generally added on top of or under the glass, yielding translucent tiles displaying a layer of color. The pieces are often etched or coated to add further visual interest or to improve performance, such as abrasion resistance. From large format to 1-inch mosaic, fused production offers flexibility in terms of tile size.

Smalti

An ancient glass tile technique combining silica sand with pigments for colorants under high temperatures, smalti tile is associated with classic tile mosaic artwork, including murals. From the Italian word literally translated as “enamels” but referring to a glaze or glass paste, smalti tiles offer a wide range of colors and textured surfaces in typically small formats. Typically made with soda and potash along with metals and metal oxides for color, the mixtures are fired and rolled into slabs to be cut by hand. The slabs can be several inches thick, if desired.

Slumped

In a third warm process, slumping, artisans use heated glass and intentionally slow its cooling process to allow for the bending and curving of the pieces. The bending of the glass tile is often used to create trim pieces, sometimes with an appealing rolled edge. Glass tile manufacturers often offer various trim pieces made by slumping so designers can specify borders and other finishing details.

Hot

This process involves molten glass that is hand cast at about 1,600 degrees Fahrenheit and hand-sheeted and hand-cut. Unseen chemical reactions produce a wide array of colors and effects, which can be rigorously monitored for uniformity. Automated rolling and bending machinery may be used. Hand-casting approaches are widely appreciated by artists and architects alike, as they allow consistent tile shaping, high aesthetic quality, as well as the creation of matching trim pieces. Manufacturers note that cast glass is generally harder to produce than other types of glass tile. Consistency and vibrancy of the through-body coloring demands accurate formulation controls, and the heating and cooling during all processes must be continuously monitored. Yet, when made properly, these glass tiles are among the most resilient. The cast products tend to be very durable, and some manufacturers recommend the tiles for higher-impact uses, such as light commercial flooring, as well as specialty environments, including outdoor and submerged water installations, such as swimming pools and water features.

Other types of glass tile include sintered tile, produced with glass powders pressed into dies and heated. Color is added early or after cooling. The technique produces a uniform look and strong finish as compared to smalti tiles, which are known for their variegated surfaces. Last, many producers offer cast tiles, which are molded from glass pieces yielding a layering or multihued product. Two other techniques are available: terrazzo glass, with its mix of glass and cements, as well as etched tile. Etched tiles typically have a translucent surface added for treatment by abrasion or acid-etching to achieve a given visual effect.

The comparison between hot and cold processes also extends to iridescent finishes. The hot process for iridescent tiles fuses the iridescence into the tile itself, rendering a more durable finish. The hot iridescent glass tiles have higher test values for scratch resistance and slip resistance, as well as unique visual characteristics. Iridescent surfaces in cold-process tiles may be easily scratched off, and the tiles may appear to have an oily finish or film.

Photo courtesy of Oceanside Glasstile/Nick Nacca

Hot or cast glass tile manufacturing requires fully melting the glass. The color is obtained through a chemical reaction at temperatures exceeding 1,600 degrees Fahrenheit.

Photo courtesy of Oceanside Glasstile/Michael Woodall

Annealing Makes Tile Appealing

One rule of glass tile production: don’t rush. “The longer the process takes to cool the glass, the stronger it is,” says Jeff Nibler, an executive with the manufacturer Oceanside Glasstile. This slow cooling process, annealing, which takes place in an oven or specialized kiln known as a lehr, relieves internal stresses caused by manufacturing. Air-cooled or non-annealed tile, on the other hand, is more prone to poor quality and cracking, he adds. Annealed glass tile is suitable for many types of applications; non-annealed products are more susceptible to environmental conditions that lead to fracturing from stresses inside the glass. Examples include susceptibility to thermal shock in outdoor applications, such as in a swimming pool or fountain.

“It is impossible to tell the difference between an annealed product and a non-annealed product with the naked eye,” adds Nibler. “The only way to visibly see this is through a polariscope.” This device employs two polarized lenses and a light source placed behind the subject glass to determine its optic character. For translucent products, the observer can see evidence of stresses, if any exist, which appear as a rainbow of colors caused by light refracting off the stress conditions. Why worry about the stresses in glass tile? These could be released in any number of ways during the life of an installation, generally through breakage under pressure or thermal differential. That’s why annealed products are specified for a range of applications whereas non-annealed products should be limited to interior walls with low-impact uses and occupancies.

Photos courtesy of Oceanside Glasstile/Chipper Hatter

To distinguish between an annealed product and a non-annealed glass tile requires a trained expert using a polariscope to evaluate the tile’s optic character. Defects, such as stresses, appear as a rainbow of refracted color.

A Hand in the Tile Process

Walking into a tile manufacturing facility illuminates some of the time-honored techniques for making high-quality colored glass pieces. At the same time, one also sees how handcrafted processes and carefully guarded formulations work side by side with modern automation and controls technologies.

Photo courtesy of Oceanside Glasstile/Katarina Shahpazova

The slow cooling process, annealing with a specialized kiln or lehr, relieves internal stresses caused by manufacturing, improves quality, and reduces cracking due to thermal stresses and underwater applications.

For cast glass tile, in the long-established, leading shops in the North America, Europe, and elsewhere, the process involves molten glass that is hand cast at about 1,600 degrees Fahrenheit and hand-sheeted and hand-cut. The producers build on extensive training and knowledge to undertake these handmade methods with reasonable precision and control. Unseen chemical reactions produce a wide array of colors and effects, which can be rigorously monitored for uniformity. Automated rolling and bending machinery may be used. Hand casting is important to many architects and artists. These methods help keep tile shapes and colors uniform, while also allowing for better aesthetics and matching. Manufacturers note that cast glass is generally harder to produce than any other types of glass tile. Consistency and vibrancy of the through-body coloring demands accurate formulation controls, and the heating and cooling during all processes must be continuously monitored. Yet, when made properly, these glass tiles are among the most resilient.

Photo by Nick Nacca, courtesy of Oceanside Glasstile

Hand-casting approaches are widely appreciated by artists and architects alike, as they allow consistent tile shaping, high aesthetic quality, as well as the creation of matching trim pieces. Hand-cast tile, marked by pure colors and a silky/consistent finish and thickness, tends to be durable and ideal for high-impact uses, such as light commercial flooring, and specialty environments, such as swimming pools.

The cast products tend to be very durable, and some manufacturers recommend the tiles for higher-impact uses, such as light commercial flooring, as well as specialty environments, including outdoor and submerged water installations, such as swimming pools and water features. In this way, glass tile is available for almost any architectural setting, allowing continuity of finish from wall to floor, from indoors to outdoors, and from dry to wet area applications.

There are two ways to transform a molten product into desired glass tile shapes: hand casting or machine rolling into a mold. The two methods are distinguished not only by production needs but also by quality of the final product. Well-maintained machinery is essential for quality control and consistency. Some high-volume producers may allow for inconsistencies and certain kinds of defects that occur in machine-rolled glass tile, in particular voids left as the molten glass is cooled and rolled. These voids and seeds (impurities) typically cannot be controlled, and they affect the appearance and optics of the resulting tiles. Rollers may also leave striations and other defects on the backs of the tiles, including voids and dimples. These roller defects can lead to difficulty removing grout from the tiles when mounted and installed, also affecting appearance. Also challenging are possible installation issues with thinset not fully bonding to the back of the tiles.

Photo courtesy of Oceanside Glasstile/Chipper Hatter

Some high-volume producers suffer inconsistencies and defects in machine-rolled glass tile (shown left), such as voids and seeds (impurities) that affect the appearance, optics, and installation success.

Hand-cast tile, when properly executed, provides for limited defects and high levels of quality control. The hand-cast products are marked by pure colors and a silky/consistent finish to the tile pieces. Molten glass is hand-ladled into the molds and observed to ensure a consistent thickness. Unique pieces of multiple sizes can be fashioned in this handcrafted process.

While one can ask glass tile makers about their processes, some architects with experience in sourcing glass tile recommend visiting the production facilities to review capabilities and product quality. At a minimum, says Joshua B. Zinder, AIA, NCARB, LEED AP BD C, founder and principal of the integrated architecture and interior design firm JZA D in Princeton, N.J., ask the manufacturers if their glass tiles are intended and suitable for a particular project application. “You could request a video or images of how a product is made, which is important for the cold processes,” he explains. “We also look at their working conditions and discuss their environmental outlook.” Participation with key industry groups like the TCNA or ANSI will help determine if their products conform to key industry standards.

For hot-process products, including hand cast and rolled, most manufacturers are able to share test results and charts. If not, architects may lack basic performance data needed to review application suitability. Similarly, Zinder notes that some claims of recycled content should be substantiated and documented. “Glass tile can be made with recycled bottle glass or other types of postconsumer and postindustrial recycled glass material,” says the architect, who designs high-end hospitality, residential, and commercial architecture, among others. “Asking for details helps, such as how the salvaged glass is obtained and sorted.” Some manufacturers access recyclable glass waste from curbside recycling programs.

Adherence to certain production standards and reporting criteria may be needed to ensure the sourced tile counts toward LEED certification.

LEED, Glass Recycling, and Hand-cast Glass Tile

For green building projects, glass tile can offer some benefits to achieving LEED certification and other sustainability goals, such as long-term durability and attractive life-cycle cost savings.⁷

Many artisan producers creating handmade glass tile use daylighting and natural ventilation for their production environments. Today’s computer-controlled kilns are relatively energy efficient, and many of the resources used, such as water, are recycled for closed-loop operations.⁸ In addition, the base materials for the products include silica (sand), which is defined as a perpetual resource and is therefore considered virtually inexhaustible and rapidly renewable, according to the European trade group Eurima.⁹ (Other organizations, such as the United Nations Environment Program, have expressed concern about the overuse of sand, while it is inarguably an abundant material.) In addition, glass tile is exceptionally durable and performs well in life-cycle assessments (LCAs).¹⁰

Photos courtesy of Oceanside Glasstile

Most glass tile has recycled content. Depending on the color of the glass tile, the products may have various amounts of recycled glass-both post-consumer and pre-consumer-from 30 percent to 98 percent total recycled content.

Photo courtesy of Oceanside Glasstile/Nick Nacca

Glass tile can be made with recycled bottle glass or other types of post-consumer and post-industrial recycled glass material. The manufacturer can detail how salvaged glass is obtained, sorted, and used.

Mounting Mosaics for Beauty, Longevity

There are several types of mounting methods for glass mosaics, and each has its own strengths and weaknesses. Sheeting, the use of mosaic tile prearranged and fixed on a paper, mesh, or film sheet, can be accomplished by hand or by machine. For the application of mosaics to sheets by hand, there are few limits on the possible sizes, colors, or patterns for the mosaic sheets. Trained mosaic sheeting artists also provide some quality controls that machines generally cannot offer. Unsurprisingly, machine sheeting can be fast and efficient when replicating a single size of sheet. However, machine capabilities tend to constrain the size, color, and pattern of the mosaics.

To mount the sheets, architects can specify mounting with mesh, a film face, or paper face. Because glass is impervious, full bonding with the thinset mortar is critical. Partial bonding or bonding to materials between other than the tile can impair long-term durability and may cause the tiles to fail.

Mesh mount allows the installer to visually check the tile during installation, and it is a relatively fast and easy application method favored by novice tile installers. On the other hand, the mesh may be visible behind installed translucent tile, leaving unexpected and undesirable grid lines behind the translucent mosaics. With mesh mount, the installer has limited time to make adjustments of the tile before setting, though cutting the sheets apart before installing would allow for additional adjustments. Another challenge is the bond, as the thinset bonds to the mesh. If the mosaic gets wet or the thinset is water soluble and compromised by moisture, the glass tiles may fail, for example by popping off the wall. Wetting of the mesh may also turn it to a black color visible through translucent tiles, unless it was treated with antimicrobials prior to mounting. TCNA does not allow mesh products for water installation, such as pools.

Photos courtesy of Oceanside Glasstile

Sheeting involves the use of mosaic tile prearranged and fixed on a paper, mesh, or film sheet in order to facilitate a proper and lasting installation. Sheeting is accomplished by machine or by hand; the former may constrain sizes and capabilities.

As opposed to the mesh on the back of the product, face-mounting using film or paper is recommended by many installers. For wet applications and pools, ANSI and TCNA recommend only the use of face-mounted mosaic products. As given in ANSI A137.2-2013: American National Standard Specifications for Glass Tile, “Face-mounting of mosaics to a sheet allows bonding to the back of the tile without interference from any mesh, glue, or other material used with back-mounted or edge-mounted mosaics. For submerged and exterior applications, face-mounted materials are recommended.”⁴

Film Face-Mounting

Film face-mounting employs a transparent film sheet to provide full bonding of the tile backs to the thinset mortar, using only a direct bond-setting method. In this approach, the installer can also see the tile while installing the mosaic; after the tile is properly set, the film is removed. The adhesive film limits adjustment by the installer, however, who also can’t easily remove thinset from the grout joints.

Paper Face-Mounting

Paper face-mounting contrasts with film application in several important ways. Similar to film, the paper sheets allow a 100 percent bond to back of tile, yet they also provide for a high degree of adjustability. The paper holds the tile in place with water-soluble glue and is removed by wetting the sheets before the thinset fully cures, allowing for an adjustable and seamlesss installation. Direct bonding may be utilized, but an alternate setting method is also possible. The installer also has the option to remount the sheets, if needed, and the paper sheets make it easier to negotiate radius conditions and other curving shapes.

Photo by Michael Woodall, courtesy of Oceanside Glasstile

Hand installation with paper sheeting is considered the premium mounting method for reasonably experienced installers, who follow TCNA recommended guidelines.

Hand installation with paper sheeting is considered the premium mounting method for reasonably experienced installers. But it has a steep learning curve so the subcontractors and installers must adhere to TCNA recommended guidelines. A few extra steps may be needed to assure a high-quality installation—but on the plus side, the highest-quality installation possible can be achieved using this method.

Installation and Inspiration

The promise and potential of tile mosaic and large-format glass tiles are evident to most architects. What is less obvious, however, are the specification and installation techniques most likely to ensure a flawless, expert finish process.

After the design team settles on a concept for the glass tile application, it is valuable to refer to the TCNA Handbook for Ceramic, Glass, and Stone Tile Installation (TCNA Handbook) to specify and design better—and to ensure attention is paid to the right concerns during the construction administration (CA) phase. “These standards are written for architects, designers, general contractors, and tile contractors in an effort to help all players in the ceramic tile industry communicate clearly and ensure successful installations,” according to James Woelfel, president of the National Tile Contractors Association (NTCA).⁵

The TCNA Handbook provides detailed information on the primary mosaic installation approach, the direct bond method. This ANSI standard referenced by TCNA is A108.16: Installation of Paper-Faced, Back-Mounted, Edge-Mounted, or Clear Film Face-Mounted Glass Mosaic Tile, which was reaffirmed in 2010. “Recommended for use with all mounted mosaic glass tile,” says TCNA, this standard provides detailed guidance on how to apply thinset, aligning the tile depth, removing the paper face, and adjusting the tile. For large-format tile, a similar standard is under development by TCNA, which is informally called the Large Format Method.

Mosaic Installation

For the primary way to set mosaics, the direct bond method, the trained installer applies thinset mortar with the proper trowel thickness, using a gauge to confirm thinset depth across the subject surface. This method also helps ensure full coverage and a complete bond, says Nibler. Because most glass tiles are transparent, the installer then smoothes out the lines with the trowel’s non-notched side to achieve a uniform surface with no visible lines. (A common error for less-experienced trade workers is that the lines from the notched side of the trowel—left as is for ceramic tile applications, for example—leave an unappealing grid or linear pattern visible under the glass mosaic.)

After this step, the installer applies the mosaic sheets to the thinset with light, even pressure, the paper side away or toward the installer. Savvy installation teams periodically check the thinset for skinning, or slight drying, which requires removal and reapplication of the mortar cement. To ensure the flattest and most uniform mosaic surface, installers lightly tap the sheets with a wooden beating block and finish hammer. This is especially helpful across sheets to level and unify sheet transitions. For walls, after about 15 to 30 minutes, the installers lightly wet the face papers, keeping them wet with a damp sponge; this eventually causes the glue to release.

Photo courtesy of Oceanside Glasstile

For mosaic installation with paper facing, installers lightly tap with a wooden beating block and finish hammer and later lightly wet the face papers to release the glue. Then the paper is peeled while the setting material is fresh to allow for adjustments.

Installers then peel the paper from the tile, starting at a corner, to see the mosaic below. This method, in which the paper is removed while the setting material is still fresh, allows for individual tile adjustment as well as visual inspection of color consistency. The goal is a consistent overall field of mosaic tiles, without traces of the sheet pattern at transitions. After 24 hours or more of curing, the installation team uses water and a nylon scrub brush to remove residual glue from the tile.

Large-Format Installation

The application of large-format glass tiles, which can range from 2.5-inch squares and up to 10-inch squares and larger, is substantially similar to mosaic glass tile installation. Yet there are a few notable exceptions.

First, the installers gauge the thinset and smooth out trowel lines, just as in the mosaic tile application. Generally, more thinset is used because these large tiles weigh more than mosaic tile elements. The large-format tiles are also carefully cleaned of contaminants and then 100 percent backbuttered with thinset to ensure good coverage and adhesion with a 100 percent bond, and also to provide complete coverage of the translucent tile for their best installed appearance. Unlike most mosaic applications, large-format tiles require the use of spacers for uniformity of spacing.

Photos courtesy of Oceanside Glasstile/Chipper Hatter

Completely covering the back of a large format tile with thinset, also known as back buttering, ensures the best possible appearance of translucent tile.

Pool Design

Installation methods for pools, water features, and other submerged water applications are different in several important respects. “Considerations when selecting tiles for pool designs include tile size and dimensional ratios,” says Amy Denny, co-owner of Alpentile, an installer specializing in glass tile pool and spa projects. “Large-format glass tiles have been known to fracture along a waterline as a result of thermal shock.” According to manufacturers, long rectangular shapes can be less stable at the center of the tile and prone to fracturing, especially if installation methods are substandard. Thickness of the tile and its overall design will also affect performance and durability.

Architects should study each product and consider how the shape, thickness, and design will function in a pool environment. Manufacturer product testing and recommendations provide good overall guidance, says Alpentile’s Denny. That’s why many architects look for manufacturers with a good quality track record and knowledgeable, available technical staff members.

Photos courtesy of Oceanside Glasstile/Michael Woodall

For pool applications of glass tile, the pool wall substrate must be properly constructed, durable, and dimensionally stable. In addition, glass tiles for these applications must be annealed (slow cooled) for best performance.

While the industry develops new standards for glass tile manufacturing and specification in pools, architects need to control as many variables as possible, including the proper construction of the pool walls, for example. Even properly installed thinset tile bond cannot perform adequately unless it is on a durable and dimensionally stable substrate.

In addition, as mentioned previously, the process of annealing (slow cooling) is essential to relieving internal stresses that may be caused during manufacturing. Annealed glass is a suitable specification for tile many types of applications, says JZA D’s Zinder, including outdoor and underwater locations where environmental conditions can lead to fracturing caused by thermal shock. For better durability and reduced chance of breakage, annealed glass-tile products are employed in these landscape and exterior applications. (For more details, see the Poolside with Glass Tiles sidebar below.)

Poolside with Glass Tiles

Glass tiles elevate swimming pools and water features in a way that calls to mind classic design, luxury appointments, and handcrafted artisanry. But selecting materials isn’t as easy as choosing the schematic concept. High-caliber products and expert craftsmanship are essential to these custom, multilayered systems in a difficult and potentially corrosive environment prone to thermal stresses.

As temperatures swing, materials are tested to their limits: expansion and contraction, chemical interactions, and changing water quality demand specialized materials designed for the task. Some glass products are too fragile for the pool environment or may not have undergone requisite testing. Glass tiles with inclusions (weak points) or made with an accelerated annealing (cooling) processes likely have invisible, unresolved stresses that under certain conditions will release (shatter).

Photo courtesy of Oceanside Glasstile/Michael Woodall

Key considerations for glass tiles in pools, spas, and natatoriums include tile size and dimensional ratios because long rectangular shapes can be less stable at the center of the tile and may be more prone to fracturing.

Key considerations for the specification of glass tiles for pools and natatoriums include tile size and dimensional ratios. “Long, rectangular shapes can be less stable at the center of the tile and thus prone to fracturing,” says Amy Denny, co-owner of Alpentile, an installer specializing in glass tile pool and spa projects. “I study each product and imagine how the shape, thickness, and design will function in a pool environment.”

Similar to other designers and installers, Denny recommends asking the manufacturer for data on product testing and recommendations. For pools, three types of mosaic mounting systems may be offered: mesh (back) mounted, plastic film (face) mounted, and paper (face) mounted. The paper-face system affords 100 percent contact with the setting material, she explains, and it does not limit creative options. Plastic film face-mounting requires the setting material to harden before the sheets are removed, making it more challenging to adjust the tiles during installation.

Mesh systems, on the other hand, are typically not recommended for pools: the semi-rigid backing does not allow the 95 percent contact between glass tile and setting material, which some codes require and many experienced installers recommend, she adds.

Last, many grouts and thinsets may not survive the rigors of pool water. The owner-operator of the pool should test such water variables as pH, calcium hardness, and total dissolved solids (TDS). Maintenance of the installed glass tiles should include regular cleaning with a stiff brush to remove the scale accretion on glass tiles near the waterline.

Setting the Standards

In these and other areas, architects designing with glass tile should be familiar with all of the relevant standards by the key groups discussed in this course. This is especially important for installing glass tile in wet areas, according to Donato Pompo, CTC, CSI CDT, MBA, an expert consultant and founder of Ceramic Tile and Stone Consultants. “Industry standards are created by industry consensus groups consisting of installers, producers, and industry experts through organizations, such as ANSI (American National Standards Institute), TCNA (Tile Council of North America), ASTM (America Society for Testing and Materials), or ICC (International Code Council),” wrote Pompo in TileLetter.⁶

Among the key challenges noted by Pompo is the lack of continuous moisture or vapor barriers and proper flashing for tile applications to on-grade slabs. He points to the standard ASTM E1643: Standard Practice for Selection, Design, Installation, and Inspection of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs, to help guide proper specification and construction—in particular, ensuring the vapor retarder continues up from under the slab to its sides and the sides of footings. For steam rooms and steam showers, specialized construction is generally required, and movement joints should use sealants meeting ASTM C920.

These and many other standards can help guide specifiers and installer teams. However, the most critical references for architects, according to David Fatula and Brian Fitzgerald, two technical experts from a major North American manufacturer, are the following:

• the TCNA Handbook, for overall information;
• ANSI A137.2-2013: American National Standard Specifications for Glass Tile, for minimum product conformance;
• and ANSI A108.16: Installation of Paper-Faced, Back-Mounted, Edge-Mounted, or Clear Film Face-Mounted Glass Mosaic Tile, for best practice in glass tile applications.

Fatula and Fitzgerald, who have contributed to the TCNA Handbook and have chaired or worked on the glass tile committees for ASTM and ANSI standards, contend that these standards are essential for avoiding common specification and installation errors by project teams with even experienced professionals.

Conclusion: Glass Tile, Done Right

Through standard development, fabrication advances, and education on best practices, the millennia-old art of handcrafted glass tile remains one of the most progressive and cutting-edge material categories. Belying its technical advances, today’s pioneers in this specialty area tout the advantage of handcrafted glass tile manufacturing and hand tile setting, mounting, and installation. This artisan heritage helps architects achieve timeless designs that are durable and sustainable with broad aesthetic range.

In order to benefit optimally from the offerings of the glass tile world, architects must be familiar with quality standards in place for glass tile production as well as mosaic tile installation. Design teams can also explore the sustainability attributes of glass tile, including the use of recycled glass. With this knowledge in hand, says the manufacturing executive Marckx, “Architects can express their deep desire for authentic and gratifying design, a colorful experience of human values, positive vibrations, and cultural vision.”

Recycled Content

Most glass tile has recycled content. Depending on the color of the glass tile, the products may have various amounts of recycled glass -- both postconsumer and preconsumer -- from 30 percent to 98 percent total recycled content. The preconsumer materials are generated during manufacturing, such as scrap and trimmings. Postconsumer materials include recycled bottle glass, known as cullet, from curbside recycling programs. This contributes to the LEED credit MRc4, which allows for a point toward certification where 10 percent of project materials by cost are postconsumer/preconsumer recycled. At 20 percent, two points may be awarded.

Regional Materials

Some building projects with potential glass tile installations may be near North American manufacturers, such as in Southern California. To increase demand for products created near the site of construction, LEED offers a credit for “building materials or products that have been extracted, harvested or recovered, as well as manufactured, within 500 miles of the project site for a minimum of 10 percent (based on cost) of the total materials value.” This includes materials permanently installed in the project but may not include elevators and mechanical equipment.

END NOTES

¹Ellis, William. Glass. New York: Avon Books Inc., 1998.

²Waage, Frederick O. Encyclopædia Britannica Inc. Britannica.com. Web. March 2016. .

³Corning Museum of Glass. “Chemistry of Glass.” 1 Dec. 2011. Web. March 2016. .

⁴The Tile Council of North America. ANSI A137.2-2013: American National Standard Specifications for Glass Tile. January 2014. Web. March 2016. .

⁵Woelfel, James. “President’s Letter.” “TileLetter,” 3 Feb. 2015. Web. March 2016. .

⁶Pompo, Donato. “Installing ceramic tile, glass tile, and stone interior wet areas.” TileLetter. 23 Jan. 2014. Web. March 2016. .

⁷U.S. Green Building Council. “LEED BD C: Retail | v1 – LEED 1.0 pilot.” Web. March 2016. .

⁸“LEED Credits.” Anna Cabo Artglass. January 2016. Web. March 2016. .

⁹Eurima. “Sustainable Natural Resources.” European Insulation Manufacturers Association. January 2011. Web. March 2016. .

¹⁰“The mining of sand, a non-renewable resource.” Green Facts. 2014. Web. March 2016. .

C.C. Sullivan leads a marketing communications agency by the same name specializing in architecture, construction, and other industries. He has produced scores of continuing education courses, articles, and technical publications globally. www.ccsullivan.com

Oceanside Glasstile has been manufacturing sustainable, hand-crafted glass tile since 1992. Made in North America the company is accessible for collaboration in custom tile design and project design as well as conventional residential, pool and commercial design.