| Color
hardener comes in a wide array of colors. There's more design
flexibility than with integral color because the finisher
controls the process. He or she decides how much color to
apply and is able to create highlights by using more than
one color.
It
takes between 60 and 120 pounds of color hardener to color
100 square feet of concrete. Lighter colors typically require
more. Most color hardener costs between 35¢ and $1.00
per square foot. But blues and greens are more, costing between
$1.20 and $6.50 per square foot. As with integral color, you
should avoid using chloride-based accelerators with this product.
Acid
Stain
Cured concrete can be colored by treating it with acid stain.
The stain, which is made from water, acid, and inorganic salts,
can be applied with a roller, brush, or garden sprayer. It's
applied to the surface but does not form a coating like paint.
Instead, it soaks in and reacts with the free lime that's
in the concrete. Free lime is not evenly distributed, so the
treatment produces an attractive mottled effect.
You
can use a single color, multiple colors, or mix colors on
the surface. Geometric patterns can be created by using a
diamond blade to score the slab prior to staining. The kerfs
can be grouted later on to create a surface that looks like
it was tiled. Free-form patterns can be created by masking
off portions of the slab and selectively staining the surface.
Manufacturers
recommend allowing new concrete to cure for two to four weeks
before staining. The slab should be carefully cleaned before
treating because surface contamination by oil or drywall dust
can mask the surface and keep the stain from soaking in evenly.
Check with the stain manufacturer before using any cleaning
solution on the slab. And whatever you do, don't acid-etch
it first because the acid will react with and "use up"
the free lime that's in the slab. The stain won't take if
there's nothing in the concrete for it to react with.
It's possible to acid-stain old
concrete, but the results are unpredictable because there's
no telling what has got ten onto or into the slab in the years
since it was poured. in general, colors are likely to be more
intense on new material than on old.
 |
Colored
Concrete Cautions |
| |
| If
you're thinking about incorporating decorative
concrete into an upcoming project, there
are some pitfalls you'll want to avoid.
No colored slab
will perfectly match the color chart, so
it's a good idea to pour and texture samples
to show the client what to expect. And if
you haven't ordered integrally colored concrete
from a particular vendor before, visit some
of his or her previous projects to see if
consistent color was maintained on jobs
with multiple pours.
Decorative concrete
work is messier than standard flatwork.
All adjacent surfaces should be masked or
protected from being hit by colored material
that drips, splatters, or, in the case of
dry-shake hardener, drifts in the breeze.
The same goes for protecting surrounding
areas against the runoff from washing your
tools or cleaning the slab.
Curing.
It's common practice to cure uncolored slabs
by misting them with water or covering them
with plastic or wet burlap. But -you should
never use those methods with colored concrete.
Adding water will lighten the color, and
covering the slab will lead to blotchiness
and staining. The correct way to cure colored
concrete is to apply a curing compound that's
compatible with the pigment.
According to
pigment manufacturers, their colors won't
fade, but weathering of concrete can make
them look faded. The way around this is
to seal colored concrete once it cures and
every two to five years thereafter This
will darken and intensify colors in much
the way that waxing an old car darkens and
intensifies its finish.
Training.
Most general contractors sub out concrete
work, especially when it receives a decorative
finish. Anyone who knows how to finish standard
concrete can probably handle integral color,
but the other methods require various levels
of training and experience. Most of the
companies that make or sell decorative supplies
hold regular training sessions. The classes
are hands-on and typically run three days.
Tuition is usually $400 to $600, which is
a bargain compared to what it costs to learn
the techniques in the school of hard knocks.
--D.F. |
|
|
<<<BACK
TO PRESS | PAGE NUMBER:
1 | 2 |
3 | 4 | 5
| 6 | NEXT
PAGE >>>
|
