When to seal your granite countertops

When to Seal Granite Countertops

It is a good idea to annually test your granite to see if there is a need to apply a sealer to the surface to increase the granites stain resistance. Keep in mind, that just because we are suggesting the test annually that you will need to apply sealer every year. Some types of granite will only need sealant applied every few years. It is always a best practice to test the granite before applying a sealant.

Many manufacturers suggest applying a sealer every year. Keep in mind, they are the manufacturer and would like you to seal more often to sell more product. It is also easier for them to use a blanket statement than to educate the homeowner on how to test their granite countertops.

In most cases, you will already know that you need a sealer before testing. Dark spots where a damp cloth sat for a few minutes or darkening around the sink areas are good indicators.

With the many stones inaccurately sold as granite, you should perform a citric acid test before buying. This test will help you determine if the stone will be suitable for kitchen applications. Many times retailers will sell marble advertised as granite. In the kitchen and areas that will see food and water, often you will want to avoid any highly absorbent natural stone. These stone countertops are more susceptible to staining.

If you did not test your granite with the water test before installation, you should do it immediately after. The water test will help you determine if you need to seal your granite, some granites may not ever require it.

When it comes to the subject of sealing granite, there is some confusion and varying opinions on what it does. Most people don’t understand how the sealing actually works on their stone countertops.

By merely testing your stone, you can quickly determine what kind of stone you have and what the absorption rate will be. The results of the test will help you determine the sealing requirements and the likelihood of staining to occur.

Testing to determine sealing requirements and stone type

The Citric Acid test will allow you to decide which type of stone countertop you have as well as the absorption rate of the stone. Granite is a silicate-based stone while marble, limestone, and travertine are calcite based. Each of these stones will have a different reaction when contacted with an acidic liquid.

Sealing your granite countertopI suggest that you test your material with the citric acid test before the installation. The acidic acid test will help you understand the characteristics of the stone. This information will be critical in determining if it is best suited for your application. It is better to find out the stone does not work before installation than finding out after installation.

Granite is the top choice for kitchens because the surface will be in contact with food and beverage spills daily. Some granites are less absorbent than others, making them an excellent choice in the kitchen. Typically, dark-colored granites have a lower rate of absorption than lighter or white-colored granites.

Some stone countertops marketed as granite may not be granite at all. Commonly marble is advertised as granite. Marble does not make good material for kitchens. Marble tends to stain, and etch form any acidic material.

Sealing granite, marble, or travertine countertops will not prevent etching. The only thing sealing helps reduce staining

The etching is a chemical reaction that occurs when the acid gets in contact with the calcite in the stone. This reaction physically alters the surface of the stone and is especially noticeable on polished countertop surfaces.

Marble, travertine, and limestone will all etch when they come in contact with any acid. Sealing the surface of these stone counters will not help to reduce etching. The etching is the result of a chemical reaction with the acid and the calcite in the stone. Etching will destroy a polished surface and make it very noticeable. A lot of times these stone countertops will have a matte finish, so when etching occurs, it will be far less noticeable. In addition to etching, these stones are also most prone to staining. If you decide to use these stones, it is best to allow them to age naturally stains and all.

Some granites are extraordinarily dense and will not absorb any liquid, including sealer. When these stones are polished, it increases their resistance to absorption, making them virtually stain resistant.

When making a selecting for the kitchen, you will want to make a selecting that is highly resistant to absorption and by default, more stain-resistant. I also make the same recommendation for bathrooms as well. There are plenty of items in the bathroom area that will stain stone countertops if not strictly adhering to proper preventive maintenance.


Perform the test on an actual sample from the slab intended for use in the installation. Acquiring the sample from the exact granite slab will assure you get an accurate analysis of the installed material.

Word of caution! If you are doing this test on an already installed and polished countertop, chose an inconspicuous locating. If the acid does etch the surface, it will be irreparable.

Perform The Citric Acid and Oil Test

You will need:
  • Two samples of your countertop material
  • Citric acid – (concentrated lemon or lime juice is best)
  • Vegetable or olive oil
  • Dropper
  • Timer
  1. Place your samples in a flat surface with good lighting
  2. Drip citric juice on to the surface until you have a dime-sized puddle in the surface
  3. Repeat the process with the vegetable/olive oil.
  4. Set the timmer
  5. Watch the surface of the sample through the puddles.
  6. Once you see the stone surface under the puddle begin to darken, note the time. If the darkening happens almost immediately, then you are dealing with a highly porous stone.
  7. If it takes 4 or 5 minutes for the darkening to occur, then the stone has reasonable stain resistance. Applying a sealer to such a stone will help increase the stain resistance and would be acceptable in kitchen applications.
  8. The stone takes 10 to 15 minutes to start darkening. Then you have a pretty resistant stone. Adding a sealer to this granite would still be highly recommended to help increase resistance.
  9. If you have a stone sample that takes 30 minutes or just never darkens you have a real winner. This stone will be stain-resistant and will never need sealing.
  10. Look at the citrus juice sample, see if there is any fizzing our bubbling. Then wipe it off and see if the polish on the surface has changed. If the surface finish has changed, then your stone has calcite in the composition and should not be used in kitchen applications. The acids from fruits and vegetables in your kitchen will eventually damage the surface of your new counters.
  11. Repeat the process on all samples you are testing.

Performing The Water Drop Test

If you are only concerned with test absorbancy, then the water drop test is the right test. The main reason for the citric acid test is to identify if your stone contains calcite and will negatively react to acidic household products and foods. The stones reaction to acid is more of a concern for new counters as it will help determine if it is safe for kitchen use.

Performing a simple water test to see if your granite countertops need to sealing is quick and easy. The water test can be performed before buying your stone or on already installed granite. I would suggest testing your granite every year to be sure you adequately protect your granite with a quality sealant.

You will need:
  • Samples of your countertop material
  • Water
  • Dropper
  • Timer
  1. If you are testing a countertop, pour about 1/4 cup of water on the counter. If you are testing a smaller sample, a few drops about creating a puddle about the size of a quarter
  2. Once you have applied the water, you should start your timer. You will want to watch the area under the water to see if it starts to darken.
  3. If the granite shows an immediate darkening after the water is applied, you have granite with a high absorption rate. You will need to apply applications of sealer at least once per year but possibly several times a year to help prevent staining. Even with the sealer, proper granite maintenance and care will need to be followed to help reduce the chances of staining. It would be good to re-test with the water test method in 3-6 months and again at 1 year.
  4. 4-5 minutes pass before darkening occurs you will then need to apply several coats of sealer. You will only need to reapply the sealant every 3-5 years. It is still best to water test the granite every year.
  5. If 10 minutes pass before darkening occurs, you be able to apply a single coat of sealer and will likely last several years before needing reapplication. It would still be wise to re-test with water to see if a new application will be required.
  6. If there is no darkening by the 30-minute mark, you can consider yourself fortunate, your granite is unstainable, and you will never need to seal the surface.


In general, white and very light colors of granite will be the most absorbent and also the easiest to detect stains should they occur. While the darkest colors, like black and greens, will be very dense and may never need sealing. The densest granites may not even absorb the sealant, and the application could dull the surface. Regardless of the color, you should test your granite to see what your sealer application requirements will be.

Keep in mind, sealing your granite only increases its resistance to staining, but it will not make it impervious to stains. You will need to follow the proper steps to care for granite and prevent staining and damage from occurring. Granite sealers are, for the most part, an excellent preventive measure for when mishaps happen. Should you have a stain already, don’t worry because there are several ways to remove stains in granite.