Problem Solvers

Efflorescence: Identifying, Preventing & Controlling

What is Efflorescence?

Efflorescence is a crystalline deposit that appears on the surface of grout joints or tile as a whitish powder or crust and is generally harmless except for appearance. A combination of circumstances causes efflorescence. First, there must be minerals (soluble salts) present in the substrate. All setting materials, including grout and thinset mixtures, used in the installation of tiles contain minerals. Minerals can also be found in the tiles. the foundation and the ground. Second, water must be present to act as a vehicle for the minerals to pass through to the surface. Third, either evaporation, hydrostatic pressure or similar force must cause the water and minerals to migrate to the surface. All three conditions must be present to produce efflorescence. Eliminate any one element and the problem will not appear, unless there is external water and minerals present. As time passes the amount of efflorescence diminishes as the original amount of minerals that were present is gradually eliminated. Also, dark grout joints exhibit more efflorescence than light colored grout. The phenomenon of efflorescence is illustrated in Figures I, II & III

How to Prevent Efflorescence

Prevent efflorescence by eliminating one of the three contributing factors. Remove the minerals in the setting materials by using only washed sand or using proprietary grout mixtures. Eliminate unnecessary water by controlling job conditions and avoiding setting tiles when rain is pending. Grouting quarry tiles at temperatures less than 50^oF invites trouble. Using Visqueen as a vapor barrier between the foundation and the ground will also help reduce the passage of water in the ground through the substrate. Seal the tile surfaces with RoVal Stone Saver or RoVal Hydro-Block WB Penetrating Sealer. These products allow the treated surface to breath, allowing moisture trapped beneath the treated surface to safely pass through (98%) while remaining water repellent and greatly reducing, if not eliminating, the amount of minerals that pass through the surface. See Figure IV.

How to Correct Efflorescence

Some efflorescence can be removed by using a stiff bristle brush, either dry, or with clean water, followed by clean water rinsing. Chemical removal, such as acid rinsing, is somewhat drastic and controversial. However, in severe case this is the only alternative. Use RoVal Fast Acting Tile & Grout Cleaner or RoVal Sulfamic Acid Crystals.

The following information is assembled in part by articles published by MMSA Materials & Methods Standards Assoc. RoVal Manufacturing expresses no warranty, either expressed or implied, as to the accurateness of these recommendations

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