Is Granite Porous? How to Seal Granite Countertops?

Granite countertops can add a beautiful and elegant touch to any kitchen while instantly bringing up the value of a home. But though granite can be an attractive asset to your living space, many wonder about its usability during day-to-day life.

In general, granite has a lot of wonderful qualities that make it an excellent choice, such as its hard to scratch, crack, and stain-resistant surface. But one issue that often comes to mind for homeowners is how porous the surface of granite countertops can be. After all, high porosity on a surface can have serious consequences if not properly addressed.

Is Granite Porous or Nonporous?

As a natural stone, granite is porous. However, granite countertops are less porous when compared to marble, limestone, and sandstone.
Granite as an igneous rock is made up of many different minerals (mainly quartz and feldspar) that range in shape and size, compacted together to form what looks to the naked eye to be one coherent piece of rock. Because of this inconsistency, granite is not a completely smooth and solid surface. Instead, it contains microscopic pores throughout its surface that can range in size and quantity, absorbing small amounts of any liquids that are applied to the area.

Luckily, this absorption doesn’t have to be a downside to granite, as you can seal the granite surface to prevent the countertop from absorbing liquids.

Granite Porosity and Permeability

Because granite is not a sedimentary rock, it has a much lower porosity level than many others. Granite’s porosity ratio ranges from 0.4% to 1.2%, and any granite countertop will fall somewhere along this porosity scale.

Is Granite Countertops More Porous Than Marble?

Granite has a much lower porosity level than marble its well-known countertop competition, marble. The porosity of marble sits at up to 2%, which can be much higher than granite, with a porosity ratio between only 0.4% and 1.2%.

The porosity also depends on the type of granite and marble. For example, according to Science Direct the Halaib Granite has a porosity of 0.42%, whereas for the Dawi marble it is 1.98%. That is nearly a 5 times more absorption rate.

When compared to granite, quartzite countertops are also more porous. Only manmade quartz performs better in this regard.

Cons of Granite Porosity

So the granite countertop is porous, but what does that mean for usability? If the liquid is left for long periods of time on an unsealed granite surface, the rock’s porous nature can cause that liquid to absorb into the counter, bringing with it bacteria and stains that live just beneath the surface.

If left untended for an extended period of time, liquids such as red wine and lemon juice can cause stains on granite. But, the porosity isn’t a bad thing in the case of water and harmless liquids. If soaked up slowly, liquids can evaporate from the surface on their own without causing any damage.

Granite Sealant

Here’s some good news: there is a simple preventative measure that you can take to make sure the small amount of porosity your granite countertops do have won’t become a major issue in the future. In general, it is always a good idea to seal your countertops. Unsealed granite can quickly absorb a liquid and leave you with a deep set-in stain in mere minutes, not to mention the fact that it can also create a breeding ground for bacteria in the one room of your home you need to be the cleanest. Therefore, it is vital that you make it a step in your regular household maintenance.

Adding a sealer to granite helps to reduce the porosity of its surface. When the sealant is applied, it prevents liquids from absorbing into the granite too quickly, which can cause damage in the form of bacteria or stains. As a granite sealant is spread over the countertop surface, it will in a sense, “clog” the porous areas of the exterior. This creates a smoother, more hygienic space for daily kitchen activities.

Is Sealed Granite Still Porous?

Sealant is a great way to reduce any porosity issues you may have with your countertops, but it does not completely prevent liquid from entering the material. This means sealed granite is still porous, especially if the sealant gets damaged. For instance, if you regularly cut food on granite or leave acidic substances on the cooktop, they can damage the seal.

It also depends on the type of countertop finish. The countertops with a polished finish are much better than the honed finish in preventing the liquids from entering inside.

So, while a sealant, when applied regularly, will greatly improve the life expectancy of your countertop, it is not an end-all for preventing stain damage or bacterial growth in your kitchen.

Many granite countertops are delivered with some kind of sealant already applied to them upon purchase, so be sure to ask when researching possible new countertop options for your home. But this original sealant application won’t keep your space in perfect condition forever.

In order to keep up maintenance on the porosity of granite, you will have to re-apply a sealer about once every year. This small amount of regular upkeep will greatly extend the life expectancy of your countertops!

Can You Seal the Granite Yourself?

Luckily, it is possible to seal granite yourself, and it may even be an enjoyable DIY project for your home. The typical granite sealant is a relatively inexpensive product that you can get at any home improvement store, such as Lowe’s or Home Depot.

Applying sealant is easy. But before you do that, perform a water drop test to find out if your countertop needs sealing. Pour a few drops of water on your stone counter and wait for 15 minutes. If the water gets absorbed, you will see slightly darker spots. It is time to apply the sealant.

Step 1: Clean the counter with mild soap and acetone.
Step 2: Shake the sealant well and spread it across a small, manageable area on the granite surface.
Step 3: Using the spreader or a clean cloth, spread the sealant to form a thin layer.
Step 4: Wait for the seal to dry.
Step 5: Repeat the process to the rest of the area until you cover the entire countertop surface.
Step 6: For best results, apply two or three coats. Granite gold recommends waiting at least 20 minutes between coats.

Applying a sealant once a year to your countertops will keep your granite looking clean and tidy while thwarting any bacterial growth or long-term damage.