Does My Countertop Need to Be Sealed? Perform These Tests to Find Out!

Date: December 26, 2019
Author: Jon Smith
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Sealing your natural stone countertop reduces the porosity of the stone. When a countertop is porous, the risk of staining is increased. When it comes to determining if your countertops need to be sealed, it can be difficult because some brands of countertops are already sealed, while other brands are left unsealed.

So, how is a homeowner supposed to tell if their countertops need to be sealed? There are a few simple tests that will help you determine if your countertops need to be sealed.

What Does a Sealer Do?

Many people mistakenly believe that a sealer makes a countertop impervious to damage or staining. However, countertops can still get stained or damaged even if they have been sealed. A sealer reduces the absorbency rate of a countertop, which gives you extra time to clean up the substance before any type of damage occurs.

Understanding How Sealers Work

Impregnating sealers contain a resin that has been dissolved in either a petroleum-based or water-based solvent. When an impregnating sealer is applied to the countertop, the sealer soaks into the pores of the countertop.

The sealer is to remain on the countertop until the recommended time has passed. Then, all of the excess sealer will be removed from the countertop. As the water-based or petroleum-based solvent evaporates, the resin hardens and creates a water-resistant barrier.

Sealers work by reducing the absorbency of a countertop. However, it’s important to note that even a sealed countertop can stain if liquids, oils, chemicals, or foods are allowed to remain on the countertop for an extended period of time.

To help prevent staining or etching, wipe up any spills immediately using an absorbent cloth. Follow by flooding the area with water and drying. Next, use a pH-neutral cleaner to clean the countertop thoroughly. Finally, buff the countertop dry to help prevent streaks or water spots from forming.

The Difference Between Etching and Stains

Many people are baffled about the difference between etching and staining. Oftentimes, water spots and rings are referred to as stains; however, this is actually etching. Countertops that contain calcite-based stones react with the acids found in fruit juices, vinegar, coffee, alcohol, and certain chemicals. Etching destroys the polish on the stone and leaves a dull spot that cannot be wiped up.

Conversely, staining occurs when a liquid seeps into the pores of the countertop. As the liquid evaporates, discoloration of the countertop can occur. This discoloration can be on the countertop surface or deep within the countertop.

Use These Tests to Determine the Porosity, Stain Resistance and Etch Resistance of Your Countertops

Performing the following tests will help you determine if your countertops are acceptable for your kitchen or your bathroom. These tests also help you decide whether or not you should seal your countertops.

  • The Lemon Test – The lemon test helps you determine how quickly your countertop will etch. To perform the lemon test, you will need a small sample of your countertop, fresh, not concentrated lemon juice, and a clock.

Pour a dime-sized puddle of lemon juice on the countertop sample. Allow the lemon juice to remain on the stone countertop for 20 minutes. Then, flood the countertop sample with water and buff dry with a soft cloth. If the polish on the countertop appears dull, the countertop contains calcite and can etch easily. If the lemon juice bubbles when it comes in contact with your countertop sample, your countertop contains calcite.

If your countertop etches easily, it can be used in a kitchen or bathroom. However, you will need to take special precautions to prevent damage to your countertop. Clean up any spills immediately and do not use any detergent on your countertop. Instead, opt for a pH-neutral countertop cleaner.

  • The Oil Test – The oil test helps you determine the absorbency of your countertops. You will need another sample piece of your countertop, some cooking oil, and a timer. Pour a dime-sized puddle of cooking oil on the sample piece of countertop.

If the countertop darkens almost immediately, your stone countertops are extremely absorbent and may not be the best type of countertop for kitchens and bathrooms. However, if you decide to use this countertop type in your kitchen or bathroom, you will need to wipe up all spills immediately to prevent staining.

If it takes four to five minutes for the countertop to darken, a sealer can help improve the stain resistance of the countertops. Multiple coats of sealant may be needed to decrease the porosity and stain resistance of your countertops. To ensure your countertops remain protected, apply a fresh coat of impregnating countertop sealer each year.

If the countertop darkens after ten to fifteen minutes, the countertop offers some protection against stains. Choose a high-quality sealer to be used. Because the countertop does not absorb liquids quickly, you want to make sure that the sealer absorbs into the countertop and doesn’t just remain on the surface. The impregnating sealer should be applied every three to five years to protect your countertops.

If it takes longer than thirty minutes for the countertop to darken, the countertop is virtually stain resistant. This type of countertop is unable to absorb impregnating sealers. If an impregnating sealer is applied to the countertop, it will remain on the surface of the countertop and not absorb into the underlying layers of material.  This kind of countertop does not need an impregnating sealer.

  • The Water TestThe water test is another test that helps to determine the porosity of a natural stone countertop. For this test, you will need another sample piece of your countertop, water, and a timer. Pour a dime-sized amount of water on the countertop.

If the countertop darkens immediately and does not bead up, you will need to apply multiple coats of an impregnating sealer to reduce the porosity of the countertop. Additionally, this type of countertop will need to be sealed annually to help protect against damage.

If the countertop darkens after four or five minutes, multiple coats of impregnating sealer will need to be applied. For this type of countertop, the impregnating sealer will need to be reapplied every three to five years to reduce the porosity of the countertop and minimize the risk of stains.

If it takes ten to fifteen minutes for your countertop to darken, a single coat of impregnating sealer should be applied to the countertop. After you initially seal the countertop, you should reapply the countertop every five to ten years.

Finally, if after thirty minutes, your countertops have not darkened, the countertop is not porous and does not need to be sealed. Instead, wipe up spills with a natural stone countertop cleaner. The risk of staining on this countertop is much less than other countertops with higher porosity levels.


No matter the type of countertop that you have, you will need to perform each of these tests annually to determine if your countertops need to be sealed. When testing on your countertop, test in an inconspicuous area, such as an inner corner or where a kitchen appliance sits on the countertop.

Sealing a countertop with an impregnating sealer is the first line of defense against staining and etching. In addition to this, wipe all spills up immediately and clean the area thoroughly with a pH-neutral countertop cleaner.

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About Jon - Website Owner

Jon Smith

Hi, my name is Jonathan Smith. I have been in the granite business for many years and have worked my way up from an installer helper to an installer and then a countertop business owner. 

I started my countertop company with very little and grew extremely fast because of my knowledge and helpfulness. I started this countertop resource for 1 main reason. That reason is that there are no countertop websites with all the correct information and none of them are from an industry expert like myself. 

I am still in the trade every single day installing countertops, educating people on the type of material they are using for their homes, and making people's dream kitchens a reality.
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