Natural stone is a proven, durable material that is available in a huge variety of options. Though it requires a minimal amount of care, it is not impervious to harm from stains, chemicals, and the like.
Sealing natural stone can help to preserve its beauty, according to Werner Nierhoff, owner of RMS Natural Stone and Ceramics.
Like manufactured products such as ceramic tile, characteristics of natural stone can vary greatly. Harder, darker stone is generally less vulnerable to staining than softer, lighter stone.
“Light stones, particularly the white ones, like the Italian carrara, tend to be softer in their makeup and therefore more prone to absorption,” Nierhoff said.
However, one stone type is not necessarily uniform, especially in large quantities, Nierhoff added.
“As a precautionary measure, I would always recommend sealing, because even the same stone can have some variation within a large area,” he said.
“If you have a few hundred square metres, or three or five thousand in a shopping mall or a hotel, the characteristics can still vary a little bit, which means it may stain in one area and may not in another area due to slight differences in density.”
Stains and surface damage can be varied, as well. Red wine spilled on white marble can cause a permanent stain if not cleaned in short order. If somehow that stain is not cleaned in a timely fashion, it could go either way.
“If it is from last night, it will be all right,” Nierhoff said. “If it is from last week, I would think it probably will still work. If it is from last year, then it’s probably too late.”
That said, a cleaning treatment might help a bit, potentially softening the stain and making it stand out less. The longer a stain is allowed to set in, however, the less impact cleaning is likely to have.
Numerous cleaning compounds are available, and it’s crucial to consult the manufacturer to determine which is appropriate.
“A lot of cleaning compounds are available which will, in most cases, remove that stain without a trace,” Nierhoff said.
Chemicals are the most damaging compound for natural stone, and are used in the industry to create certain textures for paving stones.
“The rough surface as used often outdoors around pools and the like is often achieved by using chemicals to loosen the surface and change the appearance,” Nierhoff said.
Apart from that use, chemicals should never be applied to stone, as it may do permanent damage to the surface.
After cleaning, sealing can take place, and different stone requires different sealers.
“Stone can have very different density, or absorbency, so one coat on the surface of a dense stone may be sufficient. Other stones require all-around sealing before installation. Some are well protected with just one coat over the finished surface,” Nierhoff said.
Sealers, in general, work the same way, filling every opening and crevice and effectively creating a 'skin' around the stone. Most provide an invisible layer of protection, though some are designed to enhance features.
“It is possible to have what’s called an enhancing sealer which is specifically formulated to bring out the veining in certain stones, marble in particular,” Nierhoff said.
Application is simple. For a kitchen bench, a cloth will suffice. For a larger area, a paint roller or pad is appropriate. The work is generally no more onerous than applying a single coat of paint to the surface.
More layers, however, are not only ineffective, but detrimental.
“One should also not go to the extent of applying too many coats as that will then sit on top of the others. It won’t work anymore," Nierhoff said. "It will build a film, a slippery loose film on top of an already applied sealer. You can’t seal the sealer, so to speak.”