Formerly limited in size and type, glass tile has grown into a dazzling array with numerous types, sizes, and some very intricate patterns. The design possibilities seem endless with the technology advances that have occurred. That is the evolution of the product. Modern technology has provided new manufacturing process incorporating different types of materials into the glass matrix.
There are three basic types of glass tile: cast, fused, and low temperature-coated. Each type can be further segregated, based on size, into three additional categories: large format glass tile (typically larger than or equal to 3” by 3”), mosaic glass tile (typically larger than 3/4” by 3/4” and smaller than 3” by 3”), and miniature mosaic glass tile (typically smaller than or equal to 3/4” by 3/4”).
Each product has performance considerations that should be considered prior to selection for a given application. They include:
Impact and Abrasion Resistance:Typically glass tile is less resistant to abrasion and impact than ceramic tile; an important consideration if used for floor applications.
Thermal Expansion:Glass tile expands more that ceramic tile and more movement accommodation is necessary. Properly constructed movement accommodation joints are essential for the performance of glass tile installations.
Limited Flexibility:While glass tiles may have breaking strength values equal to or higher than ceramic tiles, they are not as resistant to surface deformation. Glass tile generally requires a more rigid support system than ceramic tile.
Bonding to Membranes:Bonding some types of glass tiles to a membrane or other impervious surfaces can result in the appearance of visible moisture behind the tile, particularly when using clear glass. Consult the manufacturer prior to use of a membrane with opaque or translucent glass tile.
Submerged Environments:In submerged installations, such as a swimming pool or other water features, consult with the manufacturer for information on the chemical resistance of the glass to products used for maintenance. Some mounted glass tiles may use re-emulsifiable adhesives or the mounting system may prevent sufficient contact between the glass tile and bonding mortar, causing delamination in submerged applications. Face mounted products are preferred in wet applications.
Any substrate needs to be flat prior to installation. The common practice in tile setting of adding a little thinset here and taking away a little there to make things lay flat does not work on glass tile. Nearly all cement products shrink as they dry. If one side of glass tile is pulled tighter to the substrate than the other side by differing amounts of thinset, cracking may occur during the curing process. This is particularly an issue in larger size glass tile.
Cracks caused during the curing process when using excessive thinset may not occur for a months in some situations. Another area of mixed recommendations from glass tile manufacturers is installing over membrane systems. This is not about consensus in the manufacturing process, but about the properties of a given product in a specific application. The easy part in explaining the mixed recommendations is the membrane itself. Not all membranes are suitable for glass tile. Some are overly compressive and may work fine under ceramic, but have excessive compression and lack the support required for glass.
Another issue is the extended curing time of a latex or polymer thinset when placed over an impervious surface (such as a membrane). Without question, sandwiching a modified thinset over a membrane and under glass tile is going to cause an extended cure cycle. With translucent or opaque glass tile, this extended curing can cause the appearance of “picture framing” as the thinset is slowly allowed to dry. With larger tile this can be a source of concern to end users, lasting a month or more.
I would be adamant about receiving very specific recommendations for each glass tile product I was selling or installing. If written recommendations are not available it would be my suggestion you align with a manufacturer who has made the investment in researching their product to create those recommendations. This may sound a little dramatic on my part but let me assure you, it is based on more instances than I can count and real stories that are better left unpublished. Get a written recommendation!
An integral part of the glass tile installation process is the use of movement accommodation joints. The reason: Glass tile is highly expansive. Before a single tile is set and beginning with the sales process, movement accommodation joints should be discussed and addressed. This is a very tough aspect of the sale to an end-user and a subject salespeople and installers alike wish to avoid. It was always a battle to tell someone they needed to put a caulk joint in their tile work. These joints can be very disturbing to the end-user if they are not made aware of and educated on the necessity of movement accommodation when using expansive glass tile products.
Glass tile is no longer a product for just the very rich. It is both desirable and readily available across the economic spectrum. Working with glass requires a special understanding of the product and installation needs. It is not, as we often hear, just like tile. There are many more considerations that must be made to ensure the customers’ performance expectations are met. For salespeople and installers, taking the extra steps can lead to a highly rewarding segment of the tile market.