| Efflorescence
What causes a whitish
residue on grout?
Generally there are a few possible causes for white
residue on colored grout. When there is a whitish mineral
residue on the grout, commonly this is caused by efflorescence.
Similar to the white powder left in a drinking glass
when a glass of water is left to evaporate, efflorescence
is caused by minerals that are soluble in water being
dissolved and transported to the surface of the grout
as the water evaporates.
Typically, the minerals originate in the cement slab
below the tile or in the ground below the slab.
Except in the rarest of cases, efflorescence does not
occur from the small amount of minerals in water used
to wash a floor. Nor when tile is installed with thinset
(tile cement), are there enough soluble salts in the
thinset to cause efflorescence.
Occasionally, when tile is installed over a thick mortar
bed, the mortar could provide a sufficient amount of
soluble salts to cause efflorescence but only if moisture
is regularly passing through the mortar bed.
The next question must be where is the water coming
from? Similar to the glass of water analogy, it takes
a lot of water to dissolve enough minerals to be noticeable.
As previously stated, typical cleaning does not provide
enough water to cause efflorescence. Even saturating
the grout joints with water during periodic cleaning
generally does not cause efflorescence.
In exterior installations over concrete, rain can cause
efflorescence over time when other conditions are right
- especially with poorly compacted or porous grout.
More commonly, there can be moisture in the ground
below the slab that is always evaporating. Even when
a vapor membrane is installed below the slab, penetrations
in the membrane may allow sufficient moisture to cause
efflorescence. This moisture, invisible to eye, is steadily
traveling through the slab, the tile cement, and the
grout. More efflorescence will be observed if the concrete
and grout are more porous
How do you minimize
efflorescence?
There are generally effective ways to minimize this
problem before tiling and some less effective options
after the tile is in place.
Before tiling, if regular vapor migration is detected,
remedial steps should be considered before tiling. Alternatively,
a vapor equalization membrane can be installed before
the tile is installed. There are also companies that
sell coatings claimed to reduce moisture migration -
however, these may interfere with the ability of the
tile cement to bond to the substrate and should only
be used if both the manufacturer of the tile cement
and the manufacturer of the coating will warranty the
installation system.
After tiling, sealing the grout with a penetrating
vapor permeable sealer may help retard the rate of evaporation.
Note, some caution must be observed in selecting the
sealer - topical sealers (acrylic sealers) which coat
the grout joint and are not vapor permeable may turn
white from reactions between the acrylic and moisture
- this is not efflorescence. Rather this is similar
to the whitish haze seen with floor wax when it is applied
to a damp surface.
What is "latex
leaching" and "dirt deposition"?
Less common than efflorescence is the white residue
that can form on polymer-modified grout if the grout
is subjected to excessive moisture before the polymers
coalesce. Polymer additives are often added to grout
to provide superior properties, commonly improved chemical
resistance, reduced porosity, improved flexibility and
freeze/thaw stability. These additives are either already
in the grout as redispersible powders or are added in
liquid form. In both cases, grout mixed with too much
water or cleaned too soon, or cleaned with excess water
can cause the polymer to migrate to the surface. In
many cases (but not all), these polymers are white in
color. When the excess water evaporates, the white polymer
is exposed.
In areas with light-colored soils or near light-colored
carpeting, occasionally light-colored residue is seen
on the grout when detergents used on the tile and grout
have not been fully removed. Although the detergent
residue is often virtually invisible, it can combine
with the soil to form a sticky film that builds up over
time. Because the grout joint is commonly lower and
more porous than the tile, the dirt tends to be observed
in the grout joint. In severe cases, the dirt will also
discolor the tile.
Very often, a tile floor can be cleaned with hot water
or extremely small amounts of cleaner. Preferably, the
dirty water should be vacuumed off the floor. If not
possible, sufficient rinse water should be used to remove
all traces of the dirt and cleaner.
How do I clean off the
"white stuff" on my grout?
Solving the problem of residue on grout depends greatly
on the cause of the problem - with ongoing moisture
migration through concrete being the most difficult.
Generally efflorescence is removed with an acid. However,
grout manufacturers do not advocate the use of acids
because they attack the cement in the grout. Used judiciously
though, this can be a highly effective way of removing
efflorescence. There are several products on the market
for this - with different acids and strengths. In all
cases, extreme care should be used to protect the person
applying the acid and surrounding fixtures. Generally,
it is best to employ an experienced professional for
this type of work. Also, acid that is too strong can
strip some color out of grout (which is also undesirable)
and acid generally cannot be used if acrylic sealers
have already been applied to the grout.
After successfully removing the efflorescence, it can
only reappear if moisture is entering the system. At
this point, sealing the grout joints with a penetrating
sealer may be recommended depending on the entire tile
assembly. The sealer will minimize water entering from
above (from rain for example) and slow down the rate
of evaporation of the water entering from below. However,
they should not be used if a water sensitive material
(like mastic and some self-leveling products) was used
in the tile assembly and there is water migration through
the substrate.
For removing a whitish residue from polymer migration,
solvents or strong cleaners are needed. As there are
many different polymers that could have been used in
the grout, any one cleaner may have more or less efficacy.
Possibly, an acid could work by removing the surface
layer of grout molecules to which the polymers are attached.
For removing soapy dirt stuck to the grout, generally
multiple rinsing with clear water and some brushing
of the grout joints will be effective. As noted previously,
vacuum extraction (with a shop vac for example) provides
the easiest and best results.
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