Efflorescence is defined as a crystalline deposit, appearing as a white chalky substance, on the surface of portland cement materials such as grout. This is a natural, although undesirable, process which occurs as cement cures (hydrates). During hydration, free lime in the cement is released and rises to the surface to form a calcium carbonate deposit which is insoluble in water. Efflorescence can be controlled or avoided if certain basic installation practices are observed.

To check for efflorescence, tape a small piece of plastic (polyethylene film) on the slab to be tiled. Make sure the tape seals all of the edges. If water condensation appears under the plastic within one or two days, efflorescence will most likely occur. To avoid grouting problems a waterproofing membrane may be necessary.

Since the efflorescence effect evolves from the upward or outward movement of free lime to the surface of the grout (through the evaporative process) during curing, reducing the amount of moisture (the carrier) will reduce, if not eliminate, the possibility of efflorescence.

The primary source of controllable moisture in a tile installation is the water used when mixing grout, mortar, etc. Therefore the ideal situation calls for working as dry as possible, especially when grouting, during the original installation. (Pay particular attention to the "Application" section of "How to Grout Properly", above.)

Using Super-Tek Acrylic Grout Additive in place of water when mixing grout will automatically reduce the amount of moisture in the installation. Other precautions are:

1. Never apply tile to a concrete slab which is less than seven days old.

2. Thicker beds and thinner joints should be given longer times before grouting whenever possible. Having observed all of the precautions outlined above, the finishing touch for any water-based grout installation is "damp curing". This procedure calls for the placing of porous Kraft paper over the tile floor. (See next topic.)