Q&A
Recent queries and answers from PROSOCO’s
technical Customer Care files
Q. I’ve heard you can save time on new-construction cleandown
of masonry buildings by just applying the cleaner straight
to the wall – without soaking down the wall with fresh water
first. Is that true?
A.
You might save time on the front end – but the time and
money you stand to lose when you’re called back to the job
site to address stains and damage to the wall are not worth
the risk. “Soaking down the wall” before cleaning – known as
pre-wetting – is a tried-and-true technique that’s been used for
decades by the best in the business with good reason.
Shortcut
it at your peril. If you don’t pre-wet, you’re more likely to
cause staining on the bricks and excessive erosion of the
mortar joints. Some staining can be corrected – for a
price. We make and sell remedial cleaners for that very
purpose.
Damage the mortar joints, however, and you’ve
reduced the weather-resistance of the entire wall. Short
of repointing, that kind of damage is irreversible. When
you pre-wet, you fill the brick and mortar joint pores with
water so they can’t absorb the cleaner.
The cleaner stays
on the surface where it does its job of dissolving the job dirt
and excess mortar, and clarifying the mortar joints. Don’t
pre-wet, and the brick and mortar joints absorb the cleaner.
Inside the brick and mortar joints, where it’s not supposed to
be, the cleaner causes problems. It reacts with salts or other
elements of the masonry unit to mobilize stains and efflorescence.
Inside the mortar joint, the cleaner dissolves mortar,
weakening the joint.
That dissolved mortar can also migrate to
the surface, where it reappears on the wall as white scum. White
scum is an insoluble gray or white deposit which most conventional
cleaners won’t touch.
We make a special remedial cleaner
for that condition, too. Even though you rinse spent cleaner and
dissolved contaminants off the masonry surface after cleaning,
the absorbed cleaner stays in the wall.
When the wall gets wet
from rain or sprinklers, for instance, that cleaner goes right
back to work in the wall, mobilizing stains and dissolving the
mortar joints. Those adverse effects may continue for a long
time as long as there’s cleaner in the wall because you didn’t
pre-wet.
If you decide to paint or apply a protective treatment,
the residual cleaner can also compromise penetration, adhesion
and performance. In addition to preventing damage, prewetting
helps you get a more even application of the cleaner
over the wetted surface, which improves overall cleaning uniformity.
It also improves the efficiency of your rinse, ensuring no
residual cleaner is left. Although there are instances of cleaners
that go on “dry” – some paint strippers or poultice cleaners
used for restoration, for example – in cleaning new masonry
construction, ALWAYS PREWET.
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