Marble is a hard, durable stone that people have used for thousands of years in buildings and furnishings. Whether the naturally tumbled and pock-marked variants or the smoothed and polished marble of palaces and cathedrals, the porosity of the stone depends on the finish. Because of that, not all marble types are suitable for all construction projects.
Nature of Marble
At its most basic level, marble is a mineral rock that has formed out of limestone and other materials over the ages, eventually crystalizing into the hard material that we know and use worldwide. Since it is crystalline in nature and sedimentary, it is a porous material. Although it is beautiful, marble easily stains if left unfinished, which means it does not work well in kitchen or commercial bathroom settings where constant foot traffic and food stains are present. Instead, marble is more of a decorative material appropriate for lesser-used areas.
Tumbled Versus Polished
The more you hone and polish the surface of marble, the more difficult it becomes for stains to soak into the stone. That doesn’t mean marble becomes impervious to water damage or stains; in its natural state, or after being tumbled in a large drum with abrasive material and water to achieve a rough look, it readily soaks up water and stains like a sponge. When it is honed down and those natural dips and valleys and imperfections are smoothed over and polished into the sheen that most people are familiar with in finished marble, the surface is more resistant to water seepage and more resistant to stains.
No matter which type of marble you are working with and no matter where you have installed it, regular sealing of the material is required to keep the stone from soaking up water and other liquid deposits. You have two different choices with sealers: permeating and surface sealers. Permeating sealers penetrate the stone and bond with the molecules to create a barrier that keeps moisture from soaking down into the stone. Surface sealers coat the top layer of the stone, usually with a polished finish, protecting it from the top side rather than from within. Specialty sealers come with anti-fungal properties to ward off mold and mildew.
General stains from water and mineral buildup are a natural part of owning marble. For the most part, they can be removed through scrubbing the surface with a cleaner or using the clay-pulling method, whereby wet clay is placed over the stone and allowed to pull the stain out. Deeper stains must be sanded out. If you have rough stone, leave it as-is once the stain is sanded out. With polished stone, first sand the stain out, then use higher grits of sanding pads to achieve the level of polish of the surrounding stone. Specialty kits sold at home improvement stores have sanding pads or discs with several different grits that attach to angle grinders and can be used to grind out the stain and polish the stone.
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