Two basic types of material are used to install wall tiles for home renovations, such as a backsplash: portland cement-based mortar, which is also known as thinset, and mastic, an organic tile adhesive used only on drywall applications like backsplashes. Both materials are suitable for backsplash applications, but both materials are not suitable for each type of tile. To determine which one to use on your backsplash, look to the tile you are installing.
Stone tiles like marble, travertine, slate and granite are also used frequently on backsplash installations. With the exception of green marble, which requires an epoxy-based mortar, all stone tiles need a white thinset mortar. This is for two reasons. Stone is porous and can stain if it absorbs color from the mortar or adhesive. Stone is also extremely heavy, and while some mastics are being produced that can hold large or heavy tiles, they are not made for use with stone tiles. If you have a stone tile backsplash, stick to white thinset mortar.
Glass is becoming an increasingly common material for backsplashes. Glass tiles can work as accent pieces or as the basis for the entire backsplash. This tile requires many special materials and processes for installing it properly, and one of these is the mortar. For a successful glass tile backsplash installation, you must use a white, latex-additive thinset mortar. This is crucial because glass is transparent, and the color of the adhesive can affect it. Glass is also nonporous, so mastic cannot dry properly behind it. Thinset cures by chemical changes, so no air is required for it to cure properly.
Ceramic tiles are clay-based and have a glaze covering. They are by far the most widely used tile material for wall and backsplash applications. Mastic is designed for use with ceramic tiles. It comes ready to use in buckets of all sizes, while most thinset is sold in 50-pound bags. Because backsplashes usually are around 30 square feet of space total, it makes sense to purchase a small bucket of premixed mastic for the job if you are installing ceramic tiles. If you have other tile jobs to do in the house, however, consider using thinset for all of them.
Thinset mortar can be used for nearly all materials, while mastic should only be used for ceramic and some porcelain tiles. There are a few exceptions to this rule, however. One is green marble, which will “spall” or begin to scale and flake if it comes in contact with a wet mortar like thinset or mastic. This is why epoxy is used. The other exception is specific types of glass tile. There are a few manufacturers that require the use of epoxy for their product, even on backsplashes. Always read the manufacturer’s instructions for recommendations on mortar type before beginning the backsplash installation.