What Are Concrete
There are two categories of concrete stains - reactive and
nonreactive. Reactive stains are water-based acidic solutions containing
metallic salts that react with the concrete's lime content. Once the chemical
reaction takes place, the stain forms a permanent bond with the concrete and
won't chip off or peel away.
Non-reactive stains are water-based acrylic stains that don't rely on a chemical
reaction to impart color. Instead, they are formulated to penetrate the concrete
surface and deposit their pigment particles in the open pores.
Nonreactive stains have grown in popularity over the past few years because they
come in a much broader palette of colors than acid stains and are easier to
apply. The downside: They won't produce the same variegated, translucent color
tones characteristic of acid stains. The color effects tend to be more opaque
and more uniform.
Regardless of what stain colors you choose, be aware of the following
With acid-based stains, wide color variations are
normal. Surfaces will have a mottled, variegated appearance, and these
variations will be emphasized when the final coat of sealer is applied.
With some acid stain colors, what you see in liquid
form may not be what you get once the stain has reacted with the concrete
surface. The stain may not reveal its true color until it has been allowed to
remain on the concrete for several hours or longer. Always apply the stain to a
small test area before covering the entire surface.
Color effects will generally be more intense on new
concrete than on older or weathered concrete.
Why Use A Concrete
It boils down to one word: character. Concrete stain does more
than simply add color. Rather than produce a solid, opaque effect like paint or
colored coatings, stains permeate the concrete to infuse it with rich, deep,
translucent tones. It is important to keep in mind even when treated with
the same staining product in the same shade, no two concrete floors, walls, or
countertops will look alike due to factors such as the composition and age of
the concrete, surface porosity, texture, and environmental conditions. Some
stain manufacturers use adjectives such as "antiqued," "variegated," or
"mottled" to describe the distinctive look. It's this variability, rather
than uniformity, that gives stained concrete its broad appeal and permits an
infinite array of special effects.
Factors That Affect
The Results Of Stains
The acid in chemical stains opens the top surface of the
concrete, allowing metallic salts to reach the free lime deposits. Water from
the stain solution then fuels the reaction, usually for about a month after the
stain has been applied. Other factors that affect the outcome include:
- Cement properties and amount
- Admixtures used
- Type of aggregate used
- Concrete finishing methods
- Concrete age and moisture content when stain is applied
- Weather conditions when stain is applied
In general, cements that produce larger amounts of calcium
hydroxide during hydration will show more stain color, and higher cement
contents pro-duce more intense colors. Air-entraining or water-reducing
admixtures don’t pose a problem. However, calcium-chloride accelerators can
cause very mottled, darkened areas, and for this reason aren’t recommended.
Nonchloride accelerators don’t cause this mottling effect.
If they’re near the surface, calcium- based aggregates, such as
lime-stone, take stain readily and deepen the color of the concrete above them.
Siliceous aggregates, such as gravel, don’t react with the stain. Open
finishes achieved by floating followed by minimal troweling take more stain and
produce denser colors than do hard-troweled surfaces. However, open finishes
lose color faster because the concrete wears away. Because of this, many
contractors prefer staining hard-troweled surfaces because the stain color lasts
longer. Colors on troweled surfaces also look richer than those on floated
surfaces. But you have to grind the surface or use a higher acid concentration
to ensure adequate stain penetration.
Slabs placed in wet weather result in a richer stain color if the
concrete is stained soon after it’s placed. However, wet slabs are more likely
to effloresce, lightening the color and causing a more mottled effect in areas
where the stain doesn’t take because efflorescing salts hinder penetration. On
sunny days, the concrete can become hot and dry, and the stains won’t penetrate
as deeply into the concrete.
The continued presence of water will cause the reaction to
continue for a long time, and concrete stained blue-green will gradually turn
brown or even black. Initially, this provides nice variation to the appearance,
but eventually, nearly all the blue-green color may change to brown and black.
Because of the possible color shifts, some manufacturers advise against using
these colors for exterior concrete. Interior slabs must be placed on a
well-drained base or sub-grade and have a low moisture content before stain is
applied. Jones believes the brown-colored "flowering" of blue-green stains is
caused by oxidation of a copper component resulting from water vapor passing
through the slab. Others believe the brown color is caused by a fungus, which
can be eliminated by using sealers containing a fungicide.
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Vanguard Concrete Coating
3030 Hillcroft SW
Grand Rapids, Michigan 49548
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rights reserved by Vanguard Concrete Coating of Grand Rapids, MI. For residential floors our service area includes the Central, Southwest, & West
Michigan cities of Grand Rapids, Muskegon, Traverse City, Mount Pleasant, Midland, Bay City, Saginaw, Flint, Howell, Jackson, Lansing, Kalamazoo, South
Haven, Holland, Grand Haven and small cites in-between. For industrial &
commercial clients we service a larger area including Detroit & Ann Arbor, Ohio / OH,
Northern Indiana / IN, and Northeastern Illinois / IL cities.
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