On
Schmid's tilt-up office building job, he used glossy
solvent-based acrylic on the bottom half of the walls
and silicone-based natural took scaler on the top. The
gloss% sealer gave the walls more protection near the
ground, he says, On the other hand, he did not seat
the huge retaining wall project at all. "Stain
itself really doesn't need anything to protect it,"
he says. 'But some people feel better if it's seated."
There is one more factor, possibly the thorniest when
it comes to acid stains: cleanup.
The acid must be neutralized. Nox-Crete recommends
neutralizing the acid residue with a solution of sodium
bicarbonate and water. But there's more: The heavy metals
in many acid stains are also contaminants.
"The heavy metals that actually produce the color
are what should be the real concern," Theme says.
'If these metals get into the
groundwater they will contaminate the water system.
They are much more hazardous than the acid in the stain.
All of the residue that is to be removed after the application
of the stain must be captured, treated and disposed
of according to local regulations."
Waterborne reactive stains don't leave behind any residue
to be removed, he notes. "Once waterborne reactive
stains have been applied to a concrete substrate they
will remain there, and no washing is necessary. This
reduces the contractor's liability on the project."
