Spring 2010

Countertop Sealers

Defending Against Stains and Scratches
by Amy Johnson

Delta Performance Products tested its ICT Reactive Sealing System with oil, mustard and wine. After five hours, the surface was wiped clean, and the company reports there was no visible staining or etching. The ICT system is comprised of Counter Hard densifier and First SealZ sealer.

Photo courtesy of www.blueconcrete.com

Think about what happens to a kitchen counter every day. People splash acids on it. They spill things that stain it. They chop and slice on it. They set hot pots and dishes down on it. And they clean and clean and clean it with water and chemicals and green scrub-pads.

"Concrete countertops are countertops that are made out of concrete," says Jeffrey Girard, P.E., president of The Concrete Countertop Institute. "They're not art, they're not sculpture, and they're not merely decorative. They're countertops." Their manufacture and performance must be consistent with the form, function and aesthetics of a countertop.

In many ways a countertop serves in a harsher environment than an outdoor patio, and yet it is held to a much higher visual standard. "You see a floor from five feet away," says Mike Heidebrink, president of Cheng Concrete. "A counter is viewed from only two feet away, so it must deliver a very fine finished aesthetic."

Concrete is a material well suited for countertops. It is durable, strong, versatile and beautiful. But it is also easily misunderstood by homeowners and, unfortunately, by some contractors too. After all, if you can drive on it, they think, why can't you put a wine glass on it?

Countertops are not driveways, and they're not floors. The concrete mix is different, and the methods for pouring or casting are different.

Equally important but perhaps less understood is the difference between sealers used for flatwork and those used on countertops. The right sealer plays a critical role in making a concrete slab, however beautiful, into a functioning kitchen counter.

What customers want
To keep a kitchen counter functional as well as beautiful, there are certain performance requirements homeowners want from a countertop sealer. "The number one objective for a countertop sealer is food safety," according to Bill York, senior technical advisor for V-Seal Concrete Sealers.

After safety, the most important characteristic for most end users is chemical and stain resistance. Because unsealed concrete is porous, it is vulnerable to etching from acids like lemons or vinegar and stains from wine, even rings left by water glasses. Most customers want a sealer that will protect the concrete from this type of damage.

For home cooks, heat resistance is a significant benefit. They don't want a sealer that will discolor or melt if they set a hot pot on it. Also, a sealer needs to resist abrasion. Abrasion resistance isn't just important for keeping a countertop looking good - scratches made by cutting on the counter or dragging rough objects over it dull the finish and create microfractures where bacteria can thrive.

The last requirement on the list is the most subjective: the finish. Some customers want a high gloss for a modern, space-age look. At the other end, some customers want the counter to look just like concrete, as if there were no sealer on it. Most settle in the middle for a matte or satin finish that avoids the plastic look of a thick, glossy material, but still offers a protective coat between the food and the concrete.

What contractors can do
After years of research and product refinement, most countertop experts agree that the single perfect universal sealant remains undiscovered. So, short of perfection, how does a concrete artisan select the right sealer?

The most direct answer is to listen to proven experts, and here's one good reason: often, you're not just applying sealers, you're applying sealer systems. Manufacturers and trainers who have been working with countertops for a long time have a track record of research and continuous improvement of sealer systems. Contractors can benefit from this research by selecting one of these proven systems, usually comprised of two or more materials, and becoming trained to use it rather than trying to develop their own system through trial and error.

Also, if they've been using the same sealer for a while, they should look at what's new, especially in systems optimized for countertops. This is an area that shows continuous improvement, and even though sources agree the perfect sealer isn't there yet, the options are getting better all the time.

Training the customer is also key. The end users need to know what different looks are available with different sealers, what trade-offs might need to be made and what their role is in maintaining and protecting the sealed surface. (The gift of a trivet or cutting board at the end of the project serves as both a nice gesture and a gentle reminder.)

The type of operation a contractor runs is also a factor in choosing a sealer system to work with. A shop producing large numbers of countertops at high speeds will probably want a rapidly curing system that can be automated. Studios working at lower volumes will not want to invest in the spray equipment or space required for such a system.

Sealing options
In the early days, fabricators' options were limited. "The industry started out with floor sealers, stone sealers, even wood sealers - we had to use what was already available," Heidebrink says. Sealer technology has advanced over the years and more options are available now. "There are finally sealers that are formulated for the stringent requirements of concrete countertops," says Bob Chatterton of Surface 519. "But it is still hard to say if one material is better than another, as every sealer has different properties. Every project has different needs and conditions and every customer has different expectations. Sometimes the best a fabricator can do is make a list of what characteristics are important in a sealer, research which one covers the most items on that list and be ready to make at least one or two concessions."

Know Your Sealer Types
Here are brief descriptions of different sealing materials - and some of the qualifications and circumstances you need to consider when dealing with products in each category.

Penetrating sealers
Penetrating sealers are relatively inexpensive, easy to apply and leave no film to chip or peel. They fall into two categories, according to Jeff Girard: densifiers and repellants. Once a repellent such as silane, siloxane or fluoropolymer is applied, no other topcoat except wax can reliably be used over it, he says. Densifiers such as sodium silicates, potassium silicate and lithium silicates react with the free salt and lime in concrete to create a gel that fills the pores. "They leave no topical film build, so it is easy to get a real nice natural look," says Bob Chatterton of Surface 519, "but they are very dependant on mix design, need enough time to react with the concrete, and generally have poor to medium resistance to acids and oils."

Acrylics
Acrylics are easy to apply and relatively inexpensive. The bond well and offer some stain resistance. They will not darken the color of the concrete. They are not particularly durable or scratch-resistant, so they are often used as a base for other sealers, including wax or urethane.

Epoxies
Prized for good adhesion and excellent chemical (i.e., stain) resistance, epoxies are also very tough and quick curing. They are optically clear, high-gloss and build to a thick film, so their aesthetics appeal to customers who like the look of a glass surface. Two-part epoxies take some practice and experience to mix and apply to the best effect. Epoxies scratch easily, so they are often topped with a scratch-resistant urethane topcoat, although this combination increases cost and work time.

"Some people really like the thick build (20 to 30 mils) of a clear epoxy," says Doug Bannister, owner of The Stamp Store, based in Oklahoma City. "Epoxies are excellent at popping color.

"Epoxies are (also) self-leveling, so they compensate for flaws and unevenness in the surface. Sometimes color will settle more in low spots, so an uneven surface might have more color variation and interest, while the epoxy coating provides a smooth work surface."

Urethanes
Polyurethanes are usually more scratch-resistant and applied at a thinner film build, so they look a bit more natural, but they are not as stain-resistant as epoxy, according to Chatterton. Like epoxies, they must be measured and mixed precisely. They are also sensitive to surface preparation and may require priming. Water-based urethanes can be formulated at different gloss levels.

"Urethane won't show scratches, water spots or finger marks if you go with a satin finish," says Ben Ashby of Concrete Solutions. "We topcoat with a water-based urethane for the food preparation surface. Urethanes don't harbor bacteria. They are also easy to repair. If it gets cut you can sand the area and reapply the coating."

For high-volume operations, urethanes that cure by exposure to ultraviolet (UV) light are unrivaled for their near instantaneous curing, according to Bill York. However, the cost of the curing system, starting at $2,000, keeps them out of reach for many fabricators of kitchen countertops. York adds that a UV lamp comes with strict safety procedures that must be learned and followed. Some UV sealer products require a pass of the UV lamp 15 inches above the substrate to cure it, which can expose eyes and skin to extreme physical danger. Other UV-cured sealers allow the light to be used much closer to the surface.

Polyaspartics
These coating materials are relatively new to countertops. They offer adhesion equivalent to epoxy and scratch resistance equivalent to urethane, according to Bannister. They are extremely fast curing, so fabricators need to learn from suppliers how to work with them efficiently. Because of their relatively high price, they are used more often for commercial countertops, where fast turnaround is required. They are difficult, but not impossible, to formulate with less than a high gloss, Bannister says.

Nanotechnology hybrid
The newest entry on the countertop sealer market is a blend of acrylic and urethane, dubbed "nano" for its extremely small molecule size. These small molecules produce a tighter surface for high resistance to scratches and stains. The material is borne in an alcohol carrier, which emits an odor that dissipates in an hour or two, according to a manufacturer of the stuff.

Let's Talk About Sealers: Experts Reveal a Wide Range of Practices Fabricators' approaches to sealing countertops are as varied as their creative countertop designs. Here are some observations from manufacturers and artisans about how they protect the work:

"For customers who like a dynamic surface, a penetrating sealer can be as simple as mineral oil or olive oil. This surface will patina, change and evolve. Wears and spills are part of that evolution. It's just like a butcher block - they can re-oil it whenever they want to."
- Mike Heidebrink, Cheng Design, Berkeley, Calif.

"In my own kitchen my countertop dates back to 1988. The sealer has long since worn off. I just rub olive oil on it. That's what I like about it. Someone who wants a synthetic material that never changes wouldn't like it."
- Buddy Rhodes, Buddy Rhodes Concrete Products, San Francisco

"Now that concrete counters have been around for a while, customers know better what to expect. People looking for concrete are becoming more forgiving. They are letting concrete counters be what they are."
- Kelly Carr, Concrete Jungle Inc., Northridge, Calif.

"We start with an acrylic lacquer to pop the color. We like the color to just jump!"
- Ben Ashby, Concrete Solutions, San Diego

"Don't oversell a customer on heat resistance. My test is, can you place a pot of boiling hot water on the surface? I find when moving a pot from a gas stove to a counter, sealers fail about half the time. It doesn't hurt the concrete, but it wreaks havoc with the sealer. They should use a trivet, just like they would with Corian."
- Ben Ashby

"An artisan concrete countertop is a handmade product and it will look and wear like a handmade product. Customers should think of waxing a countertop they way they take care of a floor or fine furniture."
- Buddy Rhodes

"When I coat a table or countertop with an epoxy, pleurae, or polyaspartic, I wet-sand the coating with 1,000-grit sand paper, then buff it with heavy-grit, then fine-grit buffing compound. This rids the coating of any imperfections and makes the piece feel like a fine piece of marble. This can be very time-consuming. Fifty square feet of countertop may take two days to get perfect. This process also seems to make the piece much more scratch-resistant."
- Rick Ogden, Rick Ogden Construction, Pryor, Okla.

www.buddyrhodes.com
www.concretecountertopinstitute.com
www.concreteexchange.com (Cheng Concrete's contractor network)
www.concretesolutions.com
www.surface519.com
www.vseal.com

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