Decorative Concrete Institute

Decorative Concrete Institute

P icture a concrete coloring material that produces a unique look whenever it’s applied. No two floors or walls look the same after being treated with this material. That’s the magic of the acid-etch chemical staining process-an infinite number of possible results limited only by the creativity of the installer. It’s why installers get so involved with the process, and it’s why their customers must have realistic expectations about the outcome. They should expect variability, not uniformity.

We’re trying to make concrete look interesting, not like some other material, says Mike Miller, president of The Concretist, a well-known consultant to the decorative-concrete industry. He often combines colors from acid-etch stains, dyes, and tints in his work, and extends the range even further by applying the stains to concrete already colored integrally or with color hardeners.

The variegated and natural look of the end product is its most attractive feature, but this variability can also lead to disagreements among owners, specifiers, and installers. Because so many variables can affect the final color, contractors should provide an approval sample of stain applied to a small, concealed part of the concrete to be treated.

How stains work

Chemical stains can be applied to new or old, plain or colored concrete surfaces. Although they are often called acid stains, acid isn’t the ingredient that colors the concrete. Metallic salts in an acidic, waterbased solution react with hydrated time (calcium hydroxide) in hardened concrete to yield insoluble, colored compounds that become a permanent part of the concrete. Several companies manufacture chemical stains that are variations of three basic color groups: black, brown, and blue-green.

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

* Efflorescence

In general, cements that produce larger amounts of calcium hydroxide during hydration will show more stain color, and higher cement contents produce 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 limestone, 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, Gary Jones, president of CP Concrete Systems in Burnabv, British Columbia, Canada, prefers staining hard-troweled surfaces because the stain color lasts longer. Colors on troweled surfaces also look richer than those on floated surfaces, says Jones. But you have to sand 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 subgrade 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.

Equipment needed

Acid-etch stain finishes dont require much equipment for application. For surface preparation, you may need a grinder or a buffing machine equipped with sanding pads. Power-washing equipment also is useful. Any equipment that comes in contact with the staining liquid, such as sprayers, must resist hydrochloric acid. Brushes used to apply or spread the stain should have acid-resistant, uncolored bristles.

Workers should wear the proper safety equipment including acid-proof gloves, goggles, boots, and facemasks to filter acid vapors. And good-quality wet vacuums are highly recommended for cleanup

When to stain

The work of other trades also can affect staining results. For instance, drywall dust on a surface to be stained will react with the stain, coloring the surface differently wherever it’s present. And spills grease and oil. other lime-based materials, paint or caulk. before or after staining will produce unwanted color variations. A good relationship with the owner or project manager helps to prevent such mishaps. Project management should ensure that the floor isn’t damaged before or after staining and keep trades away from areas where preparation and staining are in progress.

If an installer other than the concrete contractor applies the chemical stain, the contractor and -installer must agree on the following:

* Pour schedule. To get a rich color, some installers begin staining with diluted materials as early as a day or two after the concrete has been placed. For uniform results, they need to stain each placement at exactly the same age.

* Jointing method. For slabs requiring sawed control joints or pattern lines, dust or sawing slurry must be removed before any of it bonds to the slab. Otherwise, stain color at the joints will differ from the color of the rest of the surface.

* Finishing -process. Although Jones likes to work on a hard-troweled surface, some installers prefer finishes that more readily accept the stain. Uniform finishing throughout the job helps to ensure more uniform stain penetration.

* Curing method. Do not use plastic sheeting, liquid membranes, or wet curing methods because they can trap moisture and cause efflorescence.

It’s often best to install chemical-stain finishes and a first coat of sealer, and then protect the floor surface with a cover before allowing other trades on the floor. Unfortunately, any protective material will affect the final appearance of the stained floor to some degree, usually by leaving an outline of its shape on the floor and by darkening the surface a bit. Don’t use any cover material that doesn’t allow water vapor to escape. Breathable cloth tarps are perhaps the best covers for preventing discoloration caused by the work of other trades.

Surface preparation

It has been said, Every step successfully completed leads to the suc cessful completion of the next step. This is certainly the case with chemical-stain work; proper surface preparation is a vital step.

First, throw a little water on the surface in several locations to see if the concrete absorbs water. If it doesn’t, curing agents or sealers may be blocking the entry of stains and must be removed. Also remove any grease and oil, paint drops, taping compounds, caulk, or other surface contaminants.

Scraping, applying solvents or stripping agents, sanding, and grinding are the principal removal methods. To pick up contaminants more easily, use stripping agents that will mix with water. If you choose to grind the surface, avoid making grinding marks that will reflect through the colored finish by using either a cup grinding head with a fine-grit (diamond or black abrasive) or diamond pad. Use a light touch, laying the cup flat on the concrete and moving it in small-diameter circles until the blemish disappears.

If a slab must be patched, use acrylic-modified, low-shrinkage materials that will accept stain. These patches will always show in the finished product, and the owner should be made aware of this.

To open up the surface for stain penetration, many installers prefer to sand floors using floor buffing machines with #60, #80, or #100 paper or screen-mesh sandpaper that allows dust to pass the pad. This process can add its own pleasing effect to the final appearance by accentuating high and low areas on the surface. (More material is removed from high spots, giving them a richer color.)

The final preparation step involves carefully washing the surface with water and detergent. Don’t use acid to clean the surface because it will diminish the effect of the stain. It’s best to scrub with a buffing machine using strip pads (preferably black) and to pick up the effluent with a good-quality wet vacuum. The surface must be clean and free of streak marks, footprints, and all residue. Anything remaining on the surface will affect stain penetration.

Sawing and patterning

Decorative cuts and sandblasted patterns achieved with stencils can enhance the appearance of stained surfaces. Timing of these operations, though, depends on the desired effect. When you want the overall stain finish to be as evenly colored as possible, cut lines and patterns after staining is complete. Stains penetrate differently around indentations. If there is to be a color change at a pattern line, cut the line first to form a barrier to stain movement. If sawed joints are to be grouted, complete the staining and sealing before grouting to help prevent grout accumulation on the unprotected stain.

Pattern lines are generally laid out with pencil or chalk. Mark only where you cut, and don’t use chalk colors that are difficult to remove, or adhere lines to the concrete surface using clear fixative sprays. Many tools are available for cutting pattern lines in concrete. Most installers use grinders or hand-held saws with tables that ride against guides. Dry-cutting diamond blades that do minimum damage to the edge of the cut are a good choice. Dust-collection devices that attach to grinders and saws capture almost all of the dust. A 1-1/2-inch extruded aluminum L angle, available in most hardware stores, makes a good saw guide.

If you cut patterns before staining, cut them just before cleaning the surface in preparation for the stain. Sawing dust contains free time that can adhere to the surface, causing color distortion. If you cut after staining, do it after the first coat of sealer has been applied.

Dramatic effects also can be achieved by applying stencils to surfaces after staining and then sandblasting to reveal plain or colored concrete in areas not covered by the stencils. These stencils are usually made from plastic materials and have adhesive backings that stick to the floor surface. One coat of sealer is recommended before sandblasting to improve stencil adhesion.

Stain application

Stain manufacturers differ on when to apply stain. Some say that a new slab must cure for 28 days before work is started. Others suggest 14 days. Installers sometimes prefer to do their work as soon as possible after the concrete is placed.

When choosing how to apply stain, keep the following things in mind:

* Colors are more intense if stain is applied soon after concrete is placed. Stain diluted with water and applied immediately can often achieve the same results as full-strength stains applied later.

* Water drives the chemical-stain reaction. To achieve color consistency, make sure the moisture content of the concrete is roughly the same for every placement colored. If one concrete placement is stained 2 days after it’s placed, then other placements should be stained when they are 2 days old for color consistency.

* Staining, sealing, and covering finished work before other construction trades return to the area saves on cleanup, achieves a better-looking installation, and makes damage repair during the rest of construction easier to handle.

There are many ways to apply stain, with each method providing a different final appearance. However, there are some general guidelines.

Sprayers often are used to apply stains, but they should be rated for acid and have no metal parts. Acid will quickly destroy metal parts, which can affect the color of the stain. Miller advises using a spray tip with a circular pattern, spraying in a pattern that goes from left to right and then right to left, with someone scrubbing the stain into the surface using a medium-bristle brush in a circular motion just behind the spray. It’s important to scrub in the stain and not just push it around. An additional spray pass just behind the scrubbing removes brush marks. This method ensures good penetration and minimal marking from either the sprayer or brush.

Additional water can be used to create different concentrations of stain color. Wetting the concrete before stain is applied is one way to do this. Following the application with water from a spray bottle is another way.

Stains applied by paintbrush will penetrate well, but care must be taken to minimize brush marks, which are not usually regarded as creative or desirable effects. Whatever stain application method is used, be sure to carefully mask surrounding areas to avoid accidental staining. Acid stains can be difficult, and in some cases impossible, to remove.

The increased interest in chemical-stain finishes is in the direction of more subtle effects. Installers fre quently dilute stains with water to produce less intense effects. For example, one contractor often applies the stain the day after the concrete is placed, starting with a 3% stain dilution (3 parts commer

cial stain to 97 parts water by volume), and then adding more acid to increase the strength to 10%. In this manner, the contractor can gradually build up color to meet owner expectations. Second and third colors can also be added in the same fashion to create color overlays.

Sometimes a stained overlay is the best solution for concrete surfaces that show damage or have been abused during construction. Commercially available overlay materials can be integrally colored, textured, and stained to provide a new range of decorative possibilities. The overlays have high flexural strength and wear resistance. As with everything involving stains, however, it’s wise to create a sample to ensure compatibility of the overlay cement with the stain and to get owner approval for the result.

Using dyes and tints

Miller states that using a chemical stain should also involve using dyes and tints, because the two work hand in hand. Dyes and tints provide color variations not available in chemical stains, can be used to treat areas that did not stain well, or can lighten the stain color.

Dyes are not chemically reactive with concrete, and their appearance is translucent. They can be organic or inorganic and diluted with either water or solvents. Jones says dyes are azochromium coloring agents fine enough to penetrate concrete surfaces, and they can create bright colors not possible with stain, such as reds and yellows. Some dyes are UV-resistant, but those that aren’t can be coated with UV-resistant sealers to make them colorfast.

Universal tints, often available in paint stores, are opaque, and the colors produced can mask deficiencies left by acid stains. Tints can also lighten the color of the stained surface.


When most of the chemical reaction is complete, a layer of colored residue with a mildly acidic pH will remain on the surface. This layer must be thoroughly cleaned off with a scrubbing machine and water mixed with detergent so the sealer will bond properly when applied to the surface. Water-based sealers, in particular, have little tolerance for residual acid. Using pH paper or pencils to test the surface pH is a good way to ensure that conditions are right.

To the water-and-detergent cleaning mix, add a tablespoon of baking soda per gallon of water to neutralize any remaining acid. Scrub with a buffing machine using soft buffing pads (green or white) or a scrub brush, and pick up the residue with a wet vacuum. Rinse until the water is clear. Allow the floor to dry 1 or 2 days before sealing.

Applying sealer

Surface sealers for exterior applications should be acrylic to allow moisture in the slab to escape. Solvent-based acrylics generally perform better than water-based products for outdoor use. Silicone-based penetrating sealers are recommended for applications where a shiny or wet look is not desirable. A good indoor application consists of one coat of solvent-based acrylic followed by a topcoat application of water-based acrylic. maintenance can be performed with additional applications of water-based acrylic sealers or waxes.

For interior slabs, three primary types of sealers are used: acrylics, urethanes, and epoxies. Acrylics are UV stable, inexpensive, and easy to apply or re-apply, as necessary. But they have the softest surface of the three and require the most maintenance. Solvent-based acrylic sealers are softer than water-based products. They also provide a wet look that greatly enhances the appearance of colored finishes.

Epoxy sealers are much harder than acrylics. Water-based epoxies bond well to concrete and provide a clear finish, but they are nonporous and do not allow trapped moisture to escape. Epoxies are probably the best choice for concrete countertops and food-preparation areas. They are not UV-resistant, and reapplication involves more elaborate preparation than for acrylics.

Urethane sealers, though the most costly, provide the most abrasive-resistant finish. However, they don’t bond well to concrete, so they must be applied over water-based epoxy applications. They are not UV-stable, and reapplication is expensive.


Concrete Construction asked several contractors what they charge to install acid-etch finishes on floors. Prices vary widely depending on the part of the country, whether the contractor is union or nonunion, and the contractor’s reputation in the market. The following are some general price ranges:

— Simple stain applications that include cleanup and a final sealer coat and involve minimal slab preparation will cost about $2 to $4 per square foot. Larger projects typically have the lowest square-foot prices.

— Stain applications with sawcut patterning and different colors between sawed lines cost $4 to $10 per square foot.

— Applications with sawed patterns and multiple color buildups are priced at about $8 to $15 per square foot.

— Sandblast stencil work, including stain, cleanup, and sealer applied only to the stenciled area, runs $12 to $25 per square foot of stencil area.

Owner acceptance

Despite the unpredictability of final results, acid-etch finishes are growing in popularity. In the past, homeowners considered staining a concrete slab if they didn’t know what else to do to improve its appearance. These days, they are going out of their way to install concrete so they can have stain finishes. Though stained concrete floors can be expensive (prices rival those for high-quality ceramic-tile installations), they are very easy to clean and maintain. Other popular applications for chemical stains include concrete countertops, sinks and showers, and plaster stucco walls-both inside and out. Stains will chemically react with any lime-based material.

In terms of color, owners seem to prefer light-tan finishes, which make up about 60% of the market. Greens and browns are popular, too, and often work well together. Black washes (1 part stain to 15 parts water) can be used to reduce the contrast between colors.

When talking to customers or specifiers about the possibilities of chemical staining, ask them to describe the look they have in mind and to provide color swatches that show variations. Show them colored photos of completed installations to help in the decision process.

If you are thinking of attempting your first acid-etch staining project, attend a training seminar. Most of the stain manufacturers and many retail outlets that sell staining products conduct educational seminars, often at no cost. Professional training opportunities are also available, for a fee.

Let Good Looks Shine Through

N o one wants to remain a dullard forever. Concrete is no exception. Blandly gray to the eye but reliable in use, traditionally it has been relegated to basements, garages, driveways and walkways as a functional surface, not a decorative one. Yet, concrete is coming into its own. Today, contractors and developers are specifying and installing intricately textured cast concrete into foyers, lobbies, garden pathways, and even countertops. But what about the cubic yards of already-installed humble gray matter? Are these surfaces doomed to remain forever mundane?

Chances are, you’ll have clients who will want to update their existing concrete surfaces from functional to fashionable. With the help of a high-quality concrete stain or refinishing product and some creativity, you can now engineer a complete makeover of the dull kid on the block. This product category offers a wealth of opportunities for contractors.

The Skinny on Stains

In the past, people seeking style have often opted to paint concrete surfaces. Particularly in the 1950s and `60s, patios, garages and basement recreation rooms sported bright-colored paint to disguise fundamentally functional surfaces. But paint, as you know, can sometimes need lots of attention. Paint sits atop the concrete and covers the natural surface texture. Since the paint does not penetrate the concrete surface, it can eventually fail because of the substrate’s inherent moisture. In fact, SherwinWilliams’ experts report that concrete’s moisture content rarely dips below 15 percent, even in existing installations.

Thus, as moisture attempts to escape the opaque coating, it forces cracks, peeling and blistering in the coating film. The traditional definition of a stain is a transparent or semi-transparent solution or suspension of color matter in a vehicle designed to color a surface by penetration without hiding it. And for this reason, today’s concrete stains offer some definite aesthetic and performance benefits. Concrete stains penetrate the porous surface and add color without hiding the concrete’s natural texture. These penetrating coatings shift with the concrete and allow the substrate to breathe.

A painted surface is just that — an opaque painted surface, says Bill Shorey of Spec-West, a Sacramento, CA-based concrete products distributor. It gives you a specific hue or color.

Staining doesn’t deliver a specific color because it is a reactionary process, he explains. The concrete itself actually gives you the final look. Depending on how old the concrete is and the condition it is in when you start out can make a lot of difference Ti The stain can enhance and intensify tile discoloration and marks in the concrete .A lot of people want that variegated ‘Old World’ look.

Decorative Concrete Institute

Shorey uses wood stain as a comparison Both concrete and wood are highly porous surfaces. As a result, penetrating stains don’t cover the substrate uniformly. Instead the coatings infiltrate the substrate’s pores and almost literally color the inner surface, as well as the outside one.

If you have an unblemished surface with a good grain you can intensify the grain, Shorey explains. Concrete isn’t just gray. You have high and lows, lights and darks, stains and black marks. When you stain it, the stain accents those different imperfections unless you put down a topcoat. It’s not a smooth, unbroken finish.

Easy Acrylic

Clean air regulations and a concern for the environment have brought about a new generation of improved water-based acrylic stains. These products are easy to apply and they clean up with soap and water. They have low odor and also have a low volatile organic compound (VOC) content, a key requirement for states with strict emissions regulations like Arizona and California.

Popular water-based concrete stains include Safety Stain II from Flex Art Company, Mason’s Select Transparent Concrete Stain from Duckback Products and the H&CT system of concrete care products from The Sherwin-Williams Company.

The stains in these lines are typically composed of acrylic resins in a water base. This formulation allows the stains to penetrate deeply into the concrete surface and adhere to the concrete to bring out color.

Another option, polymer refinishing systems — such as Concrete Solution’s Ultra Surface Concrete Polymer change the chemistry of regular concrete, causing mixtures of cement, sand, water and the polymer to adhere or bond tenaciously to an existing surface. Similarly, Micro-Top from Bomanite, a combination of liquid polymer and a

colored powder, can be applied to create surface uniformity or be blended to create an eye-catching variegation.

Limitless color combinations and graphic designs can be used to transform existing concrete and other materials into art forms without affecting surrounding materials and fixtures. Most water-based stains and overlay systems come in at least 40 colors, as well as custom colors, expanding color choices immensely over traditional acid or chemical stains, which come in a range of about eight earthtone-inspired shades.

Acid Trip

Traditional acid or chemical stains, Shorey says, yield the best-variegated finish with a nice wash of color. However, as Luposello notes, such stains can be challenging to use and offer less protection than water-based counterparts. Nevertheless, acid/chemical stains have many fans because of the stylish effects they bring to concrete surfaces. They do not have as deep of a penetration as the water-based products, but instead derive their coloration through chemical reactions between their cot components and the aggregate to which they are being applied. Because of various environmental and air quality issues, today’s acid and chemical stains generally contain some sort of water component.

Acid stains, such as Blush Tone from Brickform/Rafco Products, Lithochrome Chemstain in from L. M. Scofield Co. Rare Earth Stains, Bomanite Chemical Stain, ChlorStain from SuperStone, Kemiko Concrete Stain, and QC Patina, to name a few, chemically color concrete surfaces by combining the metallic ions with particles in the concrete to form oxides. The acid in the stains lightly etch and penetrate existing concrete, allowing the ions to form permanent insoluble chemical precipitates that remain in the a concrete’s pores.

Repair, Prepare and Refinish

Any concrete surface that is to be refinished, whether it is a floor, walkway or even a countertop must be clean ; and porous in order to ensure. c good topcoat integrity As in any job, the age-old mantra of good surface preparation is key.

First, clean the concrete to remove any grease, oil, paint or other contaminant that would inhibit the penetration of the stain. Then test the surface to see if it needs to be etched or sanded in order to permit the coating to apply easily. Luposello suggests feeling the surface and comparing it to a Piece of 120-grit sandpaper. If it feels the same, then it’s OK, he advises `’1f not, the surface needs to be ‘etched.’

If you’re using a water-based product, some experts recommend using use a 10:1 Solution of muriatic acid and water or a similar product. This process, called acid etching, opens the surface of the concrete to allow good adhesion and penetration. Rinse thoroughly several times and allow the surface to dry completely.

Other professionals advise against acid etching and instead suggest using one of the many commercial concrete preparation cleaners or strippers on the market. These products are reported to be milder but do a similar job to etching. The preparations are designed to remove dirt, grease and oil from the surface to be stained.

If you’re coating with a chemical stain, do not use muriatic acid. The purpose of using muriatic acid is to get down to clean, new cement. It will eat away the cement and leave the aggregate — that is, the sand and stone mixed with the cement to make concrete. Because of the presence of the muriatic acid, the acid stain will not react with this treated surface. And, the aggregate will not take the color. Shorey instead recommends sanding the surface to achieve the textured finish needed to accept the chemical stain. He also likes sanding for water-based stains, he says.

For either acid stains or waterborne products, proper preparation for the look you want to achieve may include pebble blasting or powerwashing to ensure a clean finish. And, again, don’t forget the critical role that moisture can play, experts urge. The concrete must be completely dry-not just the surface, Luposello says. If moisture is below the surface and gets trapped below the coating it will event eventually come up, thereby ruining the job. We recommend a 24-hour drying period between preparation and application of the first coat.

Efflorescence — the white residue caused by surfacing of concrete’s inherent salts — can be removed by a light sanding or by using a commercial masonry cleansing agent, according to the Portland Cement Association. The trade group also notes that latiance, a fine, powder-like material sometimes found on the surface of hardened concrete, should be removed by a steel scraping tool, acid etching or sandblasting/sanding, depending upon the kind of coating you will be using.

Good to Know

Application and finishing recommendations vary from brand to brand, so it’s important to follow the manufacturer’s label instructions or tech data sheets to ensure your job is the best it can be.

As a rule, however, most water-based concrete stains look best with a twocoat application. The first coat usually will penetrate and seal the concrete but not show a great deal of color. A thin second coat, applied 12 to 24 hours later over a dry surface, will bring out most of the desired color. A third coat can intensify the color even further.

Some manufacturers recommend spray applying the first coat, using either a pump or airless sprayer. Initial application with a brush, roller or pad applicator may result in lapping because the concrete may absorb the first coat faster than these types of application tools can apply the wet stain.

Wait at least 2 4 hours to walk on floor surfaces. And, for exterior surfaces such as driveways, allow surface to dry for at least seven days before running vehicles across it. Acrylic stains are often prone to tire marking, and some vehicle tire brands contain chemicals harmful to coating products. Thus, it’s not uncommon for the finish coat to lift off the surface after a vehicle has sat on it for several hours.

Polymer overlay systems generally can he Applied with a squeegee or a trowel on the surface area at a thickness of approximately 20 mils, depending on the manufacturer These systems can give an existing concrete surface not only a new, fashionable color, but they also can be worked into decorative textures with tools or stamps. Always consult the product label for the manufacturers directions and product usage recommendations.

Because chemical stains contain hydrochloric acid, always use gloves and a rubber apron when applying acid stains. And if you’re working inside or have respiratory problems, don’t forget to wear a respirator or mask.

Two coats of acid stain deliver the best results. Whether you spray or brush depends on the manufacturer’s recommendation. Once stain is on the surface, you must scrub it in with a brush as soon as it touches the concrete. Shorey suggests waiting a minimum of four hours, or until the stain is dry, before re-coating When applied, acid stains will fizz. This is due to the chemical reaction with the concrete. Continue spreading the stain in a circular or figure-eight motion until the fizzing action ceases. At least four hours after the final application, the surface must be scrubbed and rinsed clean.

Due to the hazardous content of the stain, all residues, runoff, cleaning water and absorbent materials must be discarded and disposed of in accordance with applicable state, local and federal regulations.

The Finishing Touch

Both concrete stain manufacturers and experienced contractors say a routine maintenance schedule for all colored concrete is key to preserving a top-quality appearance. Maintenance will vary depending on a number of factors, including intensity of traffic, UV exposure, geographic location, and weather conditions. Interior residential applications, for example, require less cleaning and maintenance than larger scale commercial projects.

The first step of this plan is sealing the surface following application and drying of the stain. In most cases, experts recommend applying two coats of an acrylic sealer. Products of this type will seal the surface, enhance the color, resist staining from foreign matter, as well as provide easy cleaning and maintenance. Be sure to follow manufacturer’s application instructions. Acrylic sealers, however, will not provide a high-gloss surface or prevent scuff marks from shoe soles as a commercial wax will do.

While some contractors apply a coat of urethane over the sealer, Shorey says a wax coating provides an excellent final touch. I recommend using a good maintenance contractor to apply a wax coat, Shorey says. Have that person apply sealer and then put down three to four coats of wax.

In general, the need for professional maintenance ranges from 12 to 24 months, depending on foot traffic. Maintenance wax coats should be applied periodically to assure the desired gloss level. Your stain and sealer manufacturer can provide you with the names of qualified maintenance contractors in vour area.

And, keep in mind that each sealer brand will likely affect the stain coat’s color differently. Consequently, it’s important to include the sealant step in the test sample you prepare for your clients. You don’t want to have any surprises at the end of the job, Shorey says.

Job Site Troubleshooting

Both decorative concrete and coatings experts say they cannot stress enough the unpredictability of concrete as a substrate. A contractor must always test the stain/sealer in an inconspicuous spot to ensure that the desired results will be achieved before full application, Luposello says.

But sometimes, even testing isn’t fail-safe. Concrete can simply be a fickle substrate. Shorey recalls a time when he once sold a dark acid stain to a contractor to cover a coffee shop floor. The contractor had done test samples in an out-of-the-way area, which resulted in a rich dark brown shade that the owner loved. After staining the entire floor, the contractor called Shorey with a problem: The entire job had come out jet black and the coffee shop owner could not live with it. The contractor, Shorey recalls, was desperate for a solution.

Having known from experience that a diluted muriatic acid wash would lighten the acid, I offered this as an option to the contractor, he says. Adding, if it did not work then the next option would be to re-sand the floor, put down an overlay and/or maybe both, depending on unpredictable results when using acid stain on old concrete. The contractor called Shorey several days later. He could not thank me enough, Shorey says. After being coated with a mild (20: 1) muriatic acid solution, the floor had come out a wonderful chocolate brown with nice mottling.

Concrete dyes can also solve application problems. Shorey recommends using such a product if the finished stain job has areas that did not take stain at all. For example, a 1,500square-foot floor stained dark green has one-or two-foot-square areas that are still pretty much bare concrete.

It can happen with old concrete, and it happens often, even if you’ve sanded well, Shorey says. You can fix it by mixing the dye with denatured alcohol and fogging it in over the gray area. It is transparent and mottles in with the stain, making it look like stain. but it’s not.

Whether you’re using acid stains or water-based formulations, enhancing existing concrete surfaces requires experimentation, skill and practice to discover the multitude of colors and patterns that can be achieved. While applying concrete stains at first might be daunting, learning this skill can open new doors for your business and to your clients.

A posting on the Decorative Concrete Network ( forum archives perhaps sums up the benefits of using a high-quality concrete stain: The multitude of desirable, lasting, decorative effects which are achieved by the use of stain (in lieu of paint) make for a much wiser investment, time, money, wear resistance, and lasting eye-appeal!

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