Siena Mastic 625 is a non-slip high performance, smooth spreading mastic formulated for interior installation of all types of ceramic wall and floor tile on vertical or horizontal surfaces. This product is non-flammable, freeze-thaw stable to 10º F, and exceeds ANSI-A-136.1 Type 1 specification on organic adhesive for the installation of ceramic tile. Organic mastics are not recommended for exterior use.