Winter 2007
Natural Stone Maintenance
Using the Right Products Makes
All the Difference By Stephanie Aurora Lewis
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In the Great Hall of the Library of Congress, PROSOCO's Sure Klean® Liquid Marble Cleaner was used on the white Italian marble stairways, wainscots, statuary and floors during an early 1990s restoration. The marble was grimy with years of accumulated smoke and pollutants from the building's original heating system. Plus, beeswax, used to polish the marble, had accumulated and yellowed over the decades. Conservators chose Sure Klean® Liquid Marble Cleaner because it could remove these contaminants without harm to the sensitive marble.
Photo courtesy of Gary Henry, PROSOCO
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Natural stone is an enduring material if installed, maintained and repaired by qualified and knowledgeable caretakers. Josveek Huligar, of Huligar Stone Restoration, created the Natural Stone Restoration Alliance (NSRA) with a convenient Web log for the professional tradesperson as well as for homeowners (
www.nsraweb.com). The purpose of the blog is to keep the most up-to-date products and current stone care tips available globally, to encourage interaction in the stone restoration trade, and to create an educational base fed by a community of all skill levels. Some repair projects, such as the restoration of Trinity Church in New York City and the Great Hall of the Library of Congress in Washington, D.C., necessitate professional tradesmen and professional products. Alternatively, a full range of home-based products that homeowners can utilize is available. Some new products are Lustro Italiano™ Daily Cleaners and Bonstone®'s Last Patch™ Gel.
Stone Maintenance at Home
Choosing natural stone based on its chemical and physical properties is a key to successful ease of maintenance and repairs. One of the most important considerations is whether the stone will be in a high-traffic or highly-used area. Countertops, for example, are a location where hard stones such as granite and marble are ideal. Onyx, though it is an eye-catching stone in the wide variety of beautiful colors, is not recommended for countertops and kitchen islands because of its etch-able nature and its high vulnerability to acid damage.
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Tip #1
Watermarks A watermark, commonly noticeable on marble, is actually a result of the water chemically eroding calcium from the surface. A properly selected and applied sealant will not stop this type of stain, but it will delay the watermark's damage until the water is removed and the stone is carefully cleaned. If a watermark has begun to etch into a marble surface, apply a marble polish and powder mix over the surface with a terry cloth. Finally, buff the polish to a shine. If the watermarked marble is left untreated for more than 30 days, however, the work should be left up to a professional who will resurface the stone. Professional stone restoration services could cost up to $10 per square foot.
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Now trendy, slate and limestone with a honed finish are ideal for a kitchen backsplash and for flooring. The soft rustic character of these stones can be refined through color enhancers and sealants that slightly alter the dusty stone appeal. For exterior pavers, patios and grilling surfaces, slate and granite are perhaps the best choice in natural stones because they withstand freezing and thawing with an excellent perseverance. Marble, on the other hand, holds water through its veins that will later expand with freezing, leading to destructive cracks and spalling.
One misconception regarding the application of sealants is the difference between a "coating" and a "sealant." Generally, a coating of any kind should never be applied to natural stone because it will close the natural pores and veins, thus creating a moisture barrier that will ultimately damage the stone's physical strength and possibly the natural coloration. Rather, for highly used or high-traffic areas, select and apply a superior impregnating sealant that soaks deep into the pores and veins of the natural stone. With an impregnating sealant application, water vapors are allowed to pass through the core of the stone.
Patching Indiana limestone using Last Patch™ Limestone. Photo courtesy of Paul Klees, Bonstone
"If you apply the correct sealer the first time, you very likely won't have to seal it again," Huligar says. There are three categories of impregnating sealants: solvent-based, water-based and silicone-based. Porous stones, such as travertine marble, require a thick silicone-sealant whereas dense stones, such as black granite, require a thin solvent-sealer. For the majority of other stones, a water-based sealant is most commonly applied because of its median thickness and clarity. Conversely, for low-usage areas such as a on a kitchen backsplash, a sealant is not obligatory. Exterior applications of granite and slate — such as pavers — do not need a sealer either unless they will be exposed to the possibility of spilled acidic drinks or from barbeque grease or other food debris.
| | Huligar's Homeowner
Tip #2
Oil and
Grease Stains To clean oil spots out of a slate backsplash, first place a few drops of nail polish remover (pure acetone) over the oil stain, then cover it with white baking flour for two to three hours. Clean off the flour and the oil stain is removed. If left for days or weeks the stain may seep far into the stone, requiring the services of a professional. This acetone/flour procedure can be used as a degreaser for marble countertops and travertine flooring as well.
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Regardless of the natural stone type and finish, it should be kept clean
daily. Gritty dirt and acidic liquids such as those commonly found in foods and drinks should especially be removed in a timely manner. Selecting the correct type of cleaner for the type of natural stone is important. Granite and marble, for example, should not ever be cleaned with acidic cleansers. A product such as Lustro Italiano should be applied once a month, Huligar explains. This particular product does not have any added aromas, and it is completely transparent from the bottle to its application. Daily cleaners by Lustro Italiano primarily enhance cleaning maintenance of polished and honed stones by leaving them better protected against the next acidic spill or watermark. The product is not recommended, however, for applications such as steam showers because the daily cleaner's chemical compounds can be altered by extra minerals in hard water. Additionally, this product is intended exclusively for natural stone rather than for Portland cement countertops or any other man-made products.
Cracked marble such as this can be repaired. Photo courtesy of Josveek Huligar, Huligar Stone Restoration.
Professional Maintenance
The skill of professional tradespersons and the use of professional products are vital in historic preservation and restoration projects. The Standards for Preservation by the U.S. National Park Service include, "Chemical or physical treatments, if appropriate, will be undertaken using the gentlest means possible. Treatments that cause damage to historic materials will not be used."
| | Huligar's Homeowner
Tip #3
Chips, Cracks and
Efflorescence Filling a small chip with clear nail polish can repair a travertine marble floor. Smooth the polish out with an emery board.
If a terrazzo floor suffers from differential settlement and a consequential crack, it also can be easily repaired. Insert pebbles into the crack with the bonding paste of the same terrazzo color, grind it up and shave off the extra substance with a razor blade. Finally, buff it to a preferred shine.
If a stone floor or stone wall installation has three or four tiles with cracks, cut an "X" in the middle of each tile, cut away the grout from around each broken tile, and use a chisel and a hammer to remove the tiles completely. Then replace the missing tiles with new tile and re-grout them in place. If the original, old grout is not first removed before using a chisel and hammer, then new tiles on the sides also will start cracking in the process.
If the white chalky substance called efflorescence starts to show up inside a steam shower, simply clean it off when it is dry with a soft brush. Rinse with clear water. Keep in mind that efflorescence is not harmful to natural stone, and it is not an indication that the natural stone is damaged.
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In the past, harmful coatings such as paraffin wax were used to preserve historic buildings. In time, the coatings built up a thick layer, giving the natural stone a yellow-ish glow on interior stone and a black-ish film on exterior stones. Not only was the color altered, but on exterior applications, the wax contributed to the breakdown of the natural stone's strength because moisture was trapped behind the thick coated layers.
PROSOCO's Sure Klean® Restoration Cleaner was used by professionals to gently cleanse the grime-infested paraffin wax coating off the exterior of the 1846 Trinity Church in New York City. Later, PROSOCO's Conservare H and OH Stone Strengtheners were applied to prevent any additional stone crumbling damage. For the Great Hall of the Library of Congress, PROSOCO's Sure Klean Liquid Marble Cleaner was used to gently clean accumulated smoke and pollutants from the building's original HVAC system on stairways, wainscoting, statuary and floors.
Epoxies with powdered colors to match natural stone are commonly used in a variety of stone restoration techniques. Until recently, large cracks on exterior stone cooktops or grills were repaired with polyesters and epoxies that discolor over time under UV penetration. New to the market is Bonstone's Last Patch Gel, a UV-stable epoxy product that can be used to patch exterior natural stones such as granite, marble, travertine and limestone. An instructional video is available on the company's Web site.
Natural stones have a timeless beauty that affords the owner satisfaction and luxury. Selecting, maintaining and repairing natural stone, if done in a knowledgeable manner, is an undertaking that reaps great rewards. In fact, Huligar guarantees "anything you can do to damage natural stone can be undone."
Stephanie Aurora Lewis is a freelance writer.
Resources
Bonstone Materials Corporation
Mukwonago, Wisc.
262-363-9877
Stone Repair and Adhesives - Bonstone
Josveek Huligar
Huligar Stone Restoration
Jefferson Valley, N.Y.
866-865-2897
Huligar Stone Restoration Services
PROSOCO Inc.
Lawrence, Kan.
800-255-4255
PROSOCO, Inc.
Natural Stone Maintenance
This freedom stone, an honor to the victims of Sept. 11, 2001, was delivered with a saw cut finish. After the stone was polished, a fork lift accident nicked a 5-inch chunk from the stone's surface. In the repair, Huligar Stone Restoration incorporated pieces of the natural stone and tinted adhesives. Photo courtesy of Josveek Huligar 
Damage to this memorial stone was repaired using a mix of natural stone and tinted adhesives. Photo courtesy of Josveek Huligar 
Damage to this memorial stone was repaired using a mix of natural stone and tinted adhesives. Photo courtesy of Josveek Huligar 
By creating an adhesive using varying colors from this natural stone, a repair to the crack was successfully made. Once dry, adhesive was polished flush on either side of the seam. See results on following page. Photo courtesy of Josveek Huligar, Huligar Stone Restoration 
The application of adhesive polished flush makes a smooth repair to this stone. Photo courtesy of Josveek Huligar, Huligar Stone Restoration 
The application of adhesive polished flush makes a smooth repair to this stone. Photo courtesy of Josveek Huligar, Huligar Stone Restoration 
This marble exterior was patched using Last Patch™ Gel. Photo courtesy of Paul Klees, Bonstone 
Here a Galaxy Black Granite top is repaired with the aid of copper shavings,six shades of black tinted adhesive, a cup wheel, slow RPM grinder as well as converted layered and top polishing techniques. The top polish maintained the same reflection of the rest of the surface and displayed the same characteristics of the natural stone. Photo courtesy of Josveek Huligar, Huligar Stone Restoration