How to Seal Granite Countertops, and When to Bother

Ask three people how often to seal granite and you may get three answers. That is not because anyone is lying. It is because granite varies a lot, and so do sealers.

This page lays out what the Natural Stone Institute, the trade group for the natural stone industry, and MSI, the stone supplier, each say. Then it gives you a simple test, so your own countertop can tell you the answer.

What Sealer Does

A penetrating sealer soaks into the stone and slows liquids down, so a spill sits on top long enough for you to wipe it. The Natural Stone Institute says the benefit is “the further reduction of moisture migration into an already moisture resistant surface.”

It does not make granite stain proof. The Institute says “Sealing does not make the stone stain proof, rather it makes the stone more stain resistant.”

We seal every natural stone slab before we install it. So a new Tomahawk countertop starts out sealed.

Where the Experts Disagree

The Natural Stone Institute says “Most granite countertops do not need to be sealed.” It also says “In many cases it makes sense to seal marble and granite countertops with a quality sealer,” and that a quality sealer should have “a life expectancy of ten to fifteen years.”

MSI is more cautious. One of its guides says “You also will need to seal your countertop at least once a year.” Another says “White granite countertops may need sealing more frequently than darker colors, as they are more likely to show stains.”

For honed granite, the matte finish, MSI says “Maintenance like resealing every few months is necessary to protect this finish.”

Both can be right. A dense, dark polished granite may go years without needing it. A light or honed one may need it much sooner. The Institute’s own advice is to “Consult with your supplier or sealing manufacturer specific to the type of sealer and frequency of use recommended.”

The Water Drop Test

This is how you find out what your granite needs. MSI describes it:

“To see if your granite countertop needs sealing, just splash a few drops of water on the surface. If the water beads up, your countertop is in great shape. If the water is absorbed, it’s time to re-seal.”

Try it in a few spots, especially near the sink and the stove, where the counter works hardest. Let the drops sit before you judge.

How to Seal It Yourself

MSI’s steps, in its own words:

“First, make sure the counter is clean and dry.”
“Following the directions on the container, apply the sealer with a clean, dry cloth.”
“Let dry, then apply a second coat.”
“Avoid food preparation on your counter for 24 hours to ensure it is fully cured and water-repellent.”

Two more rules from the Natural Stone Institute. Pick the right product: “If a sealer is applied in a food preparation area, be sure that it is non-toxic and safe for use.” And follow the label on that sealer over any general advice, including this page.

Things That Wear a Sealer Down

MSI’s honed granite guide says to “Avoid cleaners containing ammonia, as they can damage the stone’s protective sealer.” It also says “cleaners with acids, such as those used for tile, tub, or grout, should be avoided.”

For everyday cleaning, warm water and a mild dish soap are enough.

What About Quartz?

Quartz makers say not to seal it. Cambria, for one, tells owners to “not apply any sealers, penetrants, or topical treatments” to its countertops. If you have quartz, skip this page and wipe up spills.