Avoiding latex leaching from tile setting materials TECH TALK By Colin Cass, Techtile Consulting Pty. Ltd, Australia Abstract The use of polymer/latex type additives that improve the perfor- mance of thin-set adhesives and mortars has been in common and increasing use since the 1960s. For decades there have been occa- sional references to some of these polymer/latex additives leaching from tile work to cause problem- atic stains on the finished surface. As a consultant looking at problems with tile-work over the decades, I have noticed an increase in this specific staining, called “latex leaching” that is sometimes confused with “efflo- rescence” staining. This staining is far more difficult to treat than efflo- rescence, but it is easier to avoid. Investigations into this staining have revealed certain changes in products and procedures that are associated with this increase. This paper does not analyze the chemical aspects of the cause of this staining; rather it explains actions that can be taken by designers, specifiers, builders and tile installers to avoid this problem. Changes that make latex leach- ing more common In 1986, a Field Report of the Ceramic Tile Institute of America (86-5-1) titled “Installing Ceramic Veneers with Latex Modified Mortar & Grouts” used the term “Latex Leaching.” In May 1989, Tile & Decorative Surfaces expanded on the issue, opin- ing that “rain is one of the big- gest contributors to the leaching problem.” The problem was raised again by the Tile Council of North America (TCNA), which reported the issue in the following way, but just related it to excess water mixed with the grout, not the thin-set adhesive. It stated: “What is latex leaching and dirt deposition? Less common than efflorescence is the white residue that can form on polymer-modi- fied grout if the grout is subjected to excessive moisture before the polymers coalesce. Polymer addi- tives are often added to grout to provide superior properties, commonly improved chemi- Sponsored by This paper was recently presented at the Qualicer '18 conference in Spain. 78 TileLetter | 2018