But, as many of you know, I remain devoted to the installation side of the equation so I am not about to offer advice on how to sell glass. I'd rather offer some tips on what to do after the sale is made.
While many installers apply lessons learned handling other types of products this "tile-is-tile" mentality is risky. The successful installation of glass tile demands attention to areas that may be overlooked without causing failure in other product segments of the tile industry.
Mortar is still the preferred method of installation but today's building methods often don't allow conventional (mud or mortar) installation. Today we live in a thinset or thin-bed world where we bond directly to substrates. Glass tile can be successfully installed using these methods by experienced tile setters
In fact, glass tile installation has become so commonplace we now have American National Standards (ANSI) for their installation. In the first quarter of 2005 a completely revised ANSI A108 (American National Standards for the Installation of Ceramic Tile) will contain three new standards for glass:
• Installation of Paper Faced Glass Mosaic Tile A108.14-2005
• Alternate Method: Installation of Paper Faced Glass Mosaic Tile A108.15-2005
• Installation of Paper Faced, Back Mounted, Edge Mounted, or Clear Film-Face Mounted Glass Mosaic Tile A108.16-2005
Expansion joints a must
Let's move on to elements of the installation that are particularly critical to glass tile. Before a single tile is set, remember the need for movement accommodation. Neglect in this area is responsible for a significant number of tile installation failures.
Because glass tile has a high degree of expansion and contraction, movement or "expansion" joints are a requirement of every installation. Maximum spacing of joints needs to be every 20 to 25 feet in the interior and 8 to 12 feet in the exterior or in areas exposed to sun or moisture. A 1/8" gap should be left at all wall joints. There are many additional recommendations contained in the Tile Council of America Handbook under method EJ 171.
Please educate yourself in this critical area. The caulk or sealant, for example, should match the grout as close as possible. This requires advanced ordering and consideration during the grout selection process. Another option is a premade movement joint that can actually be seen as a desirable part of the installation.
Glass tile manufacturers typically have some very specific setting material recommendations. Mastic will never adequately dry whether used on the floor or wall. Epoxy material seems a natural selection but it is too brittle to allow the movement required by the expansive nature of glass tile. Modified thinsets are needed whenever a material is set in the thin-bed or direct bond method.
Bonding demands top shelf materials
Of course, all glass is not created equal and many possess different properties, so pay attention to the manufacturer's recommendations. It's not wise to second guess their research and field experience in the unlikely event there are any claims.
White thinsets are preferred by most to avoid shading. When liquid latex is offered, all other things being equal, it will offer superior performance due to its adhesion and drying properties. Glass tile is a top shelf product requiring top shelf setting materials for proper bonding. If the tile will be exposed to moisture make sure the setting material is rated accordingly. Some thinsets will re-emulsify in wet applications.
Spreading the thinset also differs from traditional tile. Back buttering is always a good idea on any tile over 8" x 8" and it is mandatory with any glass tile other than mosaics less than six-square inches. Glass tile is also not typically set into combed thinset. The spreading application for glass titles is key in the surface. Comb the thinset with the notched side, and then make another pass with the flat side to flatten the ridges. The back buttered tile should then be placed into the fresh thinset mortar and beat in with a beating block to assure coverage and flatness.
Notch size recommendations vary with the size of tile. Make sure the tile is dry and clean when thinset is applied. It is wise to wipe the back of the tile with a clean dry towel. One other problematic area with glass is excessive thinset applied under the tile. Tile setters often do this for "out of square" conditions or where a surface is not flat and level, we call it "padding the tile". Because thinset shrinks a bit as it dries, this is not a good idea and can result in cracked tile. The area where the tile is to be installed needs to be properly prepared before installation. The tile setter will not be able to correct out of square or plumb (flat) conditions with thinset without potentially having a detrimental effect on the tile when it is installed.
Not surprisingly, when it comes to cutting glass tile things are also a little different. Some glass tile can be easily scored and snapped with a quality cutter just like ceramic tile. Others require scoring on both sides and some can only be cut with a wet saw. Special glass blades are available though in most instances a quality porcelain blade will suffice.
Quality is a keyword here. Glass tile likes fine diamond grit and lots of it. It also likes lots of water and very little pressure when being cut. The 12" x 12" glass tile (see photo, this page) was sent to us because the installer claimed it could not be cut without excessive breakage. The saw shown along with several others had no problem cutting off a quarter-inch, chip free. We also drilled a hole in another sample of the same tile.
As you can see, no problems there either. Although space and time limitations prevented testing the diamond band saw and ring saw, I'll bet I could cut it into one big dollar sign if I wanted. Specialized equipment is not always required. One manufacturer recommends using a glasscutter and thick piece of wire for straight cuts. It doesn't get much simpler.
Grout, of course, also varies by product. Recommendations are based on joint with and the properties of the tile. Some scratch easily, most do not. Check for recommendations on either sanded or unsanded. This will also determine joint width as unsanded can not be used in a grout joint wider than 1/8". Another serious consideration is drying time.
Joints are better left ungrouted until the thinset has reached an initial cure. This can vary widely with type of thinset and environmental conditions. The bond to glass is very fragile during the initial drying stage and should not be disturbed until it has achieved adequate strength. With smaller tile, such as 1" x1" or 2" x2" a few days may be all that is necessary.
However, as the tile gets larger, drying time increases. Even in ideal environmental conditions, you should think in terms of days, not hours for larger tile. Additional time is required for low temperatures or high humidity. Sealing glass tile serves no purpose. Grout can always benefit from a sealer but once again, drying time can be extended before the application of grout sealers.
Remember, glass tile is no more difficult to work with than other tile types but it does not offer the "forgiveness" of other tile products, as such it requires both experience and strict adherence to well established installation procedures. Most important, you need to prepare your customer and installer for accommodations not customarily found in other types ceramic tile installations.