Efflorescence is a mineral deposit that sometimes leaches or
migrates to the surface of the grout. These minerals occur
naturally as part of the Portland cement which is mined and
processed from the ground. Additional minerals can also come
from the water source used with the grout or placed on top of
the grout for maintenance. Although unsightly, the mineral
deposit can be removed with a proper washing with a mild
acid solution.
Efflorescence can form shortly after grouting, resulting in a
brand-new installation that may look splotched or completely
covered with a white crust or film, to the dismay of the owner
and those associated with the installation.
Many kinds of salts have been detected in samples of
efflorescence. These include sodium sulfate, potassium sulfate,
sodium carbonate, calcium sulfate, sodium bicarbonate and
calcium carbonate.
These salts are found in cement and may also be found in
the water mixed with the grout. Custom® Building Products
incorporates chemicals within the grout to minimize the
effects of efflorescence, but efflorescence cannot be totally
eliminated. Grout mix consistency, evaporation conditions, and
actions/events beyond grout manufacturer control influence
the occurrence of efflorescence.
Because jobsite conditions change from one application to
another, it is important to adjust grouting techniques.
Dense bodied tile (porcelain), polymer-modified setting mortar,
and dense substrates prolong the time grout takes to become
firm before clean-up. Water mixed with the grout has nowhere
to go but upward, and will carry minerals to the grout surface.
A wet grout mix and/or clean-up before grout is properly firm
will create the conditions for efflorescence to occur, especially
in cooler conditions [50° - 70° F (10° - 21° C)] or when
temperature swings occur during the grout’s initial stages
of curing. ..................dave..
Grout Efflorescence problem - Bal limestone 
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