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Adding Color to Sealers
Creating Beautiful Effects Takes Knowledge and Practice
by Craig Park
Application technique is crucial to a successful project. The final finish will be very dependent on when you apply a tinted sealer, how you apply it, its thickness, and other characteristics. It takes a somewhat artistic touch, and some real practice, in order to get the final finish to meet the desired aesthetic. Depending on the method used, finishes can range from marbleized like an acid stain, to colorful blends like terra cotta. Think “faux” finish.
For the fewest problems, the easiest tint-able product is a solvent-based acrylic. It does the best job of dispersing the color as well. Next, would be a water-based acrylic, and most of the manufacturers of stains right now are water-based acrylics, or hybrids with urethane or epoxy. Typically, these are a single chemical component.
Solvent-based sealers generally give a better consistency than water-based sealers. It gives more depth, and much better durability. However, if you add too much color, it can start to break down the sealer and make it weaker. The molecular structure gets changed. Similarly, if the pigment is not compatible with the sealer it can settle in the lower areas of the pour, causing a undesirable mottled finish.
Using a colored sealer is an excellent choice to help touch up areas. Where acid staining can be temperamental, and can react differently with different mixes of concrete, sealers generally make the final project look newer and cleaner.
Colored sealers can be used interior or exterior. The application method is different, depending on the look you want to achieve. Interior applications require an acrylic hardener over the top, or a floor polish. For exterior applications, to protect a stain, or pigmented sealer, you put a clear sealer over top as your protective film.
Exterior projects are not often maintained as well, and the finish is subject to UV-degradation, pollutants and other environmental factors. This is why epoxies are not used for exterior projects. If you are using a tinted sealer for an exterior application, organic oxide pigments will be more UV-stable than non-oxide based pigments. Typically, exterior application are renovations or repairs. You can use pigmented solvenated acrylics to retrofit a stained job that is worn out. For a successful exterior application, you have to maintain the topcoat of protective sealers in order to maintain the integrity of the color.
For interior projects, it is critical that when you select a sealer, you take moisture vapor emissions into consideration. Traffic levels are also a consideration. Water-based acrylic sealers have the least amount of abrasion resistance, adding to maintenance costs. When the surface to be treated is going to have heavy pedestrian traffic, a colored sealer is probably not a good idea. Lots of foot traffic will wear it down quickly if a good maintenance program is not in place.
Moisture in the concrete substrate can be a problem in a colored sealing application. Running the calcium chloride test is important and inexpensive insurance. As with any concrete application, the simple, common-sense approach is usually best.
The biggest caveat colored sealers is their tendency to be film-forming. Because they sit on the surface, they do not penetrate like an acid stain. Most applications are surface film-forming acrylics in water-based form, and do not penetrate deeply.
If the project calls for a very hard smooth-trowel finish, getting the tinted sealer to bond can be difficult. In certain situations, they tend to peel or not bond adequately. If the preparation includes proper profiling of the surface, this should not be an issue. However, if it is not a good substrate, (e.g., one that is old, degraded or damaged) the sealer is simply going to peel taking the coloring along with it. If the preparation is right, and the test sample has been done, you will get good adherence and no problems.
If you know that the project is going to have poor maintenance, topical anything is not a good idea. Any form of topical treatments will wear through. For high traffic, low maintenance applications, sticking with an integral coloring would be best.
If the project calls for a more solid, opaque look, with less mottling and less accent coloring, a colored sealer does not make a lot of sense. Colored sealers add variety and more color density variation to a surface. If you do not want any accent colors, then you should not use colored sealer because even when it is the same color, it would give it density variation that is not natural.
The options for colored sealers are many. The variety of cost-effective and aesthetic opportunities can provide a real value add to many projects. Make sure you have selected a tinting agent that is compatible with the sealer being used. Practice the application to ensure the finishing technique to give the desired results. Inform the customer on the maintenance needed to ensure the finish lasts. Avoid situations like high-traffic, low-maintenance situations where stains or integral finishes would be a better choice.
While integral pigments give a concrete mix a solid color, and acid staining creates a finish by its reaction to the concrete, using topical tinted sealer techniques can expand the horizons of finishes for architectural flooring, allowing a wide variety of looks to meet almost any desired finish. From translucent and brighteners, variegated colors to solids of white to black, tinted sealers can add beauty to almost any architectural concrete project.
Craig Park is a free-lance writer based in San Francisco. He is an architect by training, and serves as a managing principal for a national engineering consulting practice.
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