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One
of the indicators of possible moisture intrusion is a white, powdery or
crystalline substance sometimes found on the surface of concrete, plaster and
masonry. Known as efflorescence, bloom, or sometimes effervescence, it occurs as
water containing soluble salts evaporates from the surface of an object. On
exterior surfaces it is usually only an aesthetic concern. When found indoors,
however, it indicates a water or moisture intrusion which could lead to mold
amplification and possibly structural damage.
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The
soluble salts originate from the building materials themselves or from the
ground. As water travels through the soil, wall, or building foundation, it
dissolves the salts, transporting them to the surface. Then, as the water evaporates,
it leaves the salts behind. These deposits are usually white, but can also be
green, brown or gray depending on mineral composition.
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Efflorescence
will continue as long as there is a source of salts and water. Often, salt
sources are eventually exhausted and exterior efflorescence disappears by
itself over time with normal weathering. A speedier cleanup can be accomplished
by washing the surface with water or diluted muriatic acid and a stiff brush
(non-white stains should not be washed with acid as staining could occur). Note
that water can redissolve salts and transport them back into the building
material, allowing further efflorescence. Applications of acid should be
preceded by a wetting of the surface and followed with a water or alkaline-and-water
rinse. Be sure to consult professional guidelines before handling any acid, and
to follow proper safety precautions.
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Unlike
exterior efflorescence, interior salt deposits should be addressed immediately,
as they can be signs of ground water intrusion, leaky pipes, and defective
drains, etc. Careful analysis of the situation is important not only to
determine the cause of water incursion, but also to determine if mold
amplification has occurred. If, upon analysis, no mold is found, removal of the
water source should still occur immediately to prevent potential future fungal
growth.