How on earth can marble or granite absorb water?

How on earth can marble or granite absorb water?

September 24, 2013

Although it’s not obvious to the naked eye, rocks do absorb water. This came as a pretty big surprise to a recent customer who couldn’t figure out why a salesperson would try talking her into “non-porous” quartz surfacing for her busy family bathroom. “It’s a hard surface! How can a natural stone countertop absorb water?” she wondered.

Granite bath vanity Granite vanity by LDa Architecture & Interiors; photo via Houzz

As natural stones, marble and granite countertops have varying degrees of porosity, which means that yes…they will indeed absorb water. 

Natural stones hold a network of tiny interconnected channels (sort of like the body’s capillaries), which permit penetration by liquids and gasses. These channels act like a sponge, drawing liquids in over time. The amount of absorbency varies depending on the exact type of stone. For example, denser igneous stones like granite absorb less liquid than their metamorphic counterpart, marble. But prolonged contact with moisture can affect both surfaces. For example, a puddle of water left on the counter for a lengthy period of time may show a dark spot when the water is wiped away. And highly acidic substances like orange juice, coffee, and wine will also etch some marble and granite leaving a dull mark (especially on lighter colored stones.)

Marble bath vanityMarble bath vanity by LDa Architecture & Interiors; photo via Houzz

If countertops are left unsealed, spills can easily penetrate the surface. There are products like Caesarstone and Neolith which have far fewer openings and channels for absorbing liquids, and probably that is why the salesperson was trying to convince her for man made quartz. Caesarstone and Neolith are great options for high moisture areas like the bathroom, but there’s no need to worry that water will ruin marble or granite in the bath. Stone sealers like DuPont’s Countertop Sealer are highly effective for protecting natural stone countertops from liquids.

If you do have granite or marble countertops, here’s an easy way to test your sealant. Place a few drops of water on the surface. Does the water bead? You’re in good shape. Is it absorbed into the stone pretty quickly? Time to re-seal. 

We convinced this particular client that, with the proper sealant and maintenance, the granite countertop she desired would be just fine in her busy bathroom. Do you have questions about the protective sealant on your own countertop? Are you looking for product recommendations to seal your stone countertops? Our natural stone experts at Marble and Granite, Inc.  can help. You can even purchase recommended sealant and adhesive products on our website


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