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Artist James
Howell of New York, whose work captures the graduation
of gray, chose to go with a burnished gray floor in his
studio to complement his artwork. The floor, with all
of its subtleties, was created by Alan Bouknight Contracting
in Minneola, New York. The lofts architectural design
was by Deborah Berke & Partners Architects LLP and
won the AIA award for 1999. |
It's
all in the blend
When you hard trowel colors together,
you're actually blending them for a more natural look, Ralston
says. "Look at a piece of natural slate, stone or bark
and you'll see a subtle blending of colors. That's what you're
trying to accomplish with your trowel. You're burnishing for
the visual effect, not to create a scratch-resistant surface
or a surface that cleans easier."
The more you trowel, the more mottled
the coloring appears --which isn't always a good thing. When
you overtrowel integrally colored concrete you may end up
giving clients a mottled effect rather than the color-consistent
surface they wanted. And if you really overtrowel hard concrete
-- and this is especially true with power trowels -- the aluminum
in the mix and the steel in the blades can get so hot it will
bum and blacken.
Going through the steps
Alan Bouknight, owner of Azzarone Contracting
in Minneola, New York, has been burnishing concrete for nearly
10 years. In the last year, he says, his company has made
a "quantum leap" in perfecting the process, thanks
in part to new tools, new techniques and being smart enough
to learn from mistakes. "We're willing to see how far
we can push the limits of concrete," he says. "It
has an inherent beauty if you know how to coax it out."
For a burnished finish -- "The
right terminology is a hard-steel-trowel burnished finish"
-- first strike the surface with a straightedge to make sure
it's fairly level, pass with a bull float and, when the concrete
is ready, come in with a machine and hit it once or twice
with shoes or pans to flatten it, says Bouknight. The drag
from the oversized shoes works the fines and the cream to
the surface while the vibration of the machine shakes the
mixture and the heavier aggregates sink. The oversized shoes
help to distribute the material and fill in the hills and
valleys.
Next, remove the shoes and go over the
surface with your stainless steel finish blades to help create
a polished finish. During each stage, the concrete keeps getting
harder and harder and you must determine when -- and if --
to get on it again. Each time you machine trowel, you need
to increase the speed and pitch of the blade, Bouknight says,
because you're building up friction and heat with the drag
and that can help bum the floor.
A pattern is also important. "You
need to go in different directions so you won't get waves
in the floor; you want it to stay flat. Typically, you make
passes like north to south and then east to west to give you
nice coverage between coats. It's a lot like painting,"
says the seasoned contractor.
The method he just described, he says,
will produce a burnished -- almost marbleized metallic-look
to the floor.
Burn, baby, burn
Bouknight remembers when the standard
for finishing concrete floors was to give the client a burnt
floor. During his boyhood, he recalls accompanying his father
or grandfather to jobsites in New York City some evenings
and "You could see sparks fly off the blades. That's
how many times they'd trowel it." Burnt floors are hard
as steel, he explains, and it didn't matter if they were blackened.
"The floors were going to be covered up with carpet or
linoleum anyway."
Today, "We don't have to
bum the floor as much because we have plenty of additives
to make it strong. We can avoid the bum and get a beautiful
opulence. Each time you make a pass, you're layering the burnish
marks, which gives a sense of depth to the floor. It may look
rough or coarse, but it feels like hard silk."
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