Epoxy mortars advised Typically, fiberglass mesh backed stones must be installed with a suitable epoxy setting material. Standard portland cement-based setting materials may not bond with the resinous backing/adhe- sive, leading to the potential for either immediate or long-term bond failure. Additionally, the high alkalinity of the cement-based mortar may have a negative effect on certain backing types, possibly causing bond failure, especially in wet or submerged areas. Stones with fiberglass and/or resin backing may not be suitable for wet or submerged applications; there- fore, it is advised that you work closely with your supplier to deter- mine suitability of a specific mate- rial for a particular application. TheTile Council of NorthAmerica, in its Handbook for Ceramic, Glass, and Stone Tile Installation, 2015, regarding Fiberglass Mesh Reinforced Stone, notes that “Such reinforced stone tiles require epoxy bonding mortar.” 1 This includes all reinforced backed stone. The limitations and/or cautions sections of technical data sheets for portland cement-based thin set mortars often include written pro- hibitions against using the product with moisture-sensitive stone or resin-backed tiles or stones. These cautions will frequently direct you to use an epoxy-based adhesive by the same manufacturer. It has been a common practice STONE ––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––– UltraCare™ Penetrating Plus Stone, Tile & Grout Sealer is a premium, natural-look, water- based penetrating sealer that provides maximum protection against most common stains for all interior and exterior natural stone (marble, limestone, sandstone, slate, granite, travertine, etc.), unglazed ceramic tile, masonry and grout. The product can also be used as a pre-grouting sealer. www. mapei.com. NOTE: The exact link to the UltraCare Penetrating Plus Stone, Tile & Grout Sealer is: http:// www.mapei.com/public/US/ products/2028300662-penetrat- ing-plus-stone-tile-grout-sealer- en.pdf or http://bit.ly/2zKMlnz. 80 TileLetter | December 2017