TECH TALK ––––––––––––––––––––––––––––––––––––––––––––––––––––––––– Portland cement mortar is used to install ceramic, glass, and natural stone tiles in an area that may not thoroughly dry out in use (e.g. swimming pools and gang showers, etc.) or where initial drying is inhibited (between tile and impervious substrates), it is recommended that the complet- ed installation be allowed to dry out thoroughly before exposure to water. This drying period can range from 14 to more than 60 days depending upon the tem- perature and humidity and other climatic conditions.” The issues caused by this delay in curing and drying emphasize the need to specify and use rap- id-setting adhesives for all tiling where a delay in curing is likely to cause problems. The cause of latex leaching The problem of latex leaching is not widespread on external tiling. This proves that the adhesives, mortars and installation systems used are suitable and meet the needs of the industry. However, under certain conditions, some components of the latex/polymer modified adhesive leach out and cause staining. Investigations at more than a dozen sites with latex leaching in Australia revealed a common cause. All the instances occurred when rain fell on uncovered and ungrouted tiling. In one apart- ment complex, rainfall charts and construction diaries were used to show that the four tiled decks that were suffering latex leaching were all exposed to rain before they were grouted. The six unaf- fected decks at the complex were grouted before it rained. The lifting of tiles during investi- gations almost a year later revealed water still trapped in the ribs of tile adhesive. These decks have an acrylic waterproofing membrane applied over the screed. Often, the residual water had caused the tile adhesive to discolor. This discoloration was present where water had access to the grooves in the adhesive, but was not pres- ent where the adhesive rib was closed off. Clearly, grouting the tiling helps prevent latex leaching, since even though the grout would allow some moisture to pass, it appears to prevent rainwater from filling Photo No. 4. The rainwater that entered under the tile before grouting has leached a brown material from the adhesive (possibly lignin). The latex leaching that appeared was sometimes a yellow/brown color. 86 TileLetter | 2018