How to Seal Granite and Marble Countertops
One of the most common questions we hear is whether natural stone countertops need to be sealed. Ask three people whether you should seal granite countertops, and you’ll get three different answers.
As it turns out, there’s a good reason for this range of opinions. Not all stone countertops need to be sealed. Some types of granite, like Ubatuba granite for instance, is so dense that it won’t absorb anything anyway (has a very low absorption rate and very low chance of staining).
However, the vast majority of natural stone countertops do need to be sealed once in awhile. This is particularly true of counters with a honed finish. For these stones, sealant plays a vital role in keeping your countertop resistant to stains. Sealant also makes it easier to keep your countertop clean and looking good.
Sealing natural stone is important because most stones are porous — Quartz, which is engineered from natural stone, is the exception to this rule. Porous stones have small channels or pores in the rock, which are usually filled with air. An extreme example of a porous rock is pumice stone, where air channels are clearly visible.
The porosity of a stone is influenced by the number of channels, or micro-voids, in the stone itself. Granite has a reputation as a particularly non-porous stone. Marble is usually more porous.
In countertops, these channels are much smaller. However, their presence means that food or water can seep into the stone, leaving stains. By using a sealer or impregnator on the stone, you’ll prevent liquids from seeping into the counter.
How Often Should You Seal Your Countertops?
The next most common question we hear is how often you should seal your countertop. Many salespeople will recommend sealing granite every six months to one year. Others say it should never need sealing, and a number of people fall somewhere in between.
If you’re not sure whether your stone countertops need sealing, there are a couple simple tests to help you figure it out:
Mineral Oil Test
- - Put a few drops of mineral oil in an out-of-the-way spot on your counter
- - Wait ten minutes, then wipe up the mineral oil
- - If a dark stain shows when you wipe up the mineral oil, it’s time to reseal your countertops.
Don’t worry if the mineral oil leaves a mark. Even if your counters need to be sealed, the dark spot from the mineral oil will evaporate in about 30 minutes.
Water Drop Test
- - Sprinkle a few drops of water on the counter.
- - Check to see whether the stone darkens and absorbs the water. If it absorbs the water in four minutes or less, the stone needs to be resealed.
How do I know if my surface is still adequately sealed?
Please carry out the following water test; place a tablespoon of water on the treated surface for 20 minutes, blot up the water with a tissue, pressing hard to soak up any water in the texture of the surface. If the water is absorbed or leaves a dark mark the surface needs more sealing.
Since it takes just a few minutes and no special materials, this is an easy test to do every few months.
We recommend that you decide whether to seal your countertops based on what your countertops need, rather than on an arbitrary calendar. Some counters don’t need any sealant, and this is normal.
Quartz, which is a crushed rock combined with resin, never needs sealant. Some granite counters are so dense that they don’t need it, either. Using sealant on these counters will actually give the stone a hazy or stained appearance unless wiped off properly.
Sealing Granite, Marble, & Natural Stone Countertops
Sealing granite, marble or natural stone countertops is a relatively easy process that usually takes less than an hour.
- - A cleaner designed for natural stone
- - Microfiber cloths
- - Granite or natural stone sealer
Step 1: Deep Clean the Stone You Plan to Seal
Cleaning the counter well ahead of time will ensure you’re sealing only the counter and will help the sealant absorb more evenly. There are several recipes for DIY granite and natural stone cleaners, and there are also a wide variety of natural stone cleaners available in stores.
It’s a good idea to remove any stains as part of this cleaning process because the sealant will also help to lock in stains — which, of course, is something you want to avoid.
If you have a few problem stains you’d like to remove before sealing, start by identifying the source of the stain. This will help you to treat it properly. The Natural Stone Institute provides a detailed list of stains on natural stone, and how to remove them.
After cleaning, dry the counter thoroughly. If there is any doubt whether the stone is completely dry, error on the side of caution. Sealers require very dry stone to perform at their highest.
Step 2: Apply Sealer With a Soft Cloth, Lambs Wool of Soft Brush
Application of any sealer should be in accordance with the manufacturer’s instructions. Some manufacturers provide specific techniques and sealer amounts required for various stone types and their finish ie polished, honed, flamed. Read the directions and inquire with a representative for further clarity.
Some companies will recommend 1 coat and others may recommend 2 or more. An optimal result with any manufacturer’s sealer is typically associated with the following:
- Make yourself aware of any precautions listed by the manufacturer before you start your project
- ALWAYS TEST PRODUCT ON A SMALL AREA AND WAIT 24 HOURS FOR DESIRED RESULTS
- Start with a clean, dry stone
- Apply the proper quantity of sealer
- Allow for the manufacturers recommended dwell times between coats.
Applying the sealant itself is straightforward. However, a bit of preparation beforehand will save you some trouble later.
Since sealants are applied as sprays, it will splatter on nearby surfaces if you don’t take precautions. Protect any surfaces you don’t want sealant on. Use plastic wrap on faucets, sinks or stovetops to protect them from the sealant.
We also think it’s a good idea to protect backsplashes and walls while you’re sealing. Just grab a magazine (or any other thin material you don’t mind getting sealant on). Place it along the seam between the wall and the counter while you’re sealing.
With homemade granite sealers, shake the spray bottle before use to ensure the ingredients are well mixed. With commercial granite sealers, follow the instructions for mixing.
Once you’ve sprayed the counter, leave the sealant for approximately five minutes to allow it to soak into the stone. If the stone sealer you’re using specifies a different length of time, follow the manufacturer’s recommendations.
It’s best to apply sealer in small areas instead of over the whole surface at once. Since sealer doesn’t stay on the counter for long, this will let you wipe it off when needed.
Step 3: Remove the Sealer
Next, remove the excess sealer from the areas you’ve sealed. Some of the sealant will be absorbed by the stone itself. However, once a stone is sealed, there’s usually a bit of excess sealant on the surface.
Using a soft cloth, wipe up any sealer left on the surface. We like microfiber cloths for this purpose. They’ll soak up leftover sealer without leaving fiber on the counter. Do not let the sealant dry on the counter.
In some cases, you won’t have any sealer to remove. This means that the sealer has been fully absorbed by the stone, and it’s possible the perfect amount of sealer has been applied. It is always advised that the stone be thoroughly wiped down after the final application. In the event you notice any residue, most manufacturers recommend using the sealer itself to re-activate and wipe off any excess.
More likely, however, is that your natural stone counters could use another coating of sealer. If this is the case, go on to step four.
Step 4: Apply Additional Coats of Sealant (As Needed)
Applying more than one coat of sealer is normal. In fact, in some cases it’s recommended to ensure an even coverage.
The more porous the stone, the more likely you’ll need to apply additional coats of sealant. Luckily, more absorbent stone also means less waiting time between coats of sealant.
In general, it’s a good idea to wait at least 15 minutes before applying a second coat of sealant. This will allow the first layer to be fully absorbed by the stone. If you’re using a solvent-based sealant, the stone should look dry before you apply the next layer of sealant. With water-based sealants, the stone may still have a wet look.
Some sealants, particularly granite sealants, will recommend waiting at least 30 minutes between applying coats of sealant. If the manufacturer’s instructions specify a different time period, follow their recommendations.
How to Seal Granite Countertops
What Not to Use
When you’re sealing your granite countertops, there are various things you don’t want to use.
Avoid sealers with:
- - Citrus ingredients
- - Linseed oil
- - Silicon based sealers
- - Siloxane sealers
There are several recipes available online for DIY granite sealers that use either citrus solvents or linseed oil (or both!). Avoid these recipes. Both citrus and linseed oil will discolor your granite. That’s why we suggest you use mineral oil instead of citrus oil to test whether your counters need sealing.
What to Use for Sealing a Granite Countertop
The best sealers for granite will be:
- - Impregnators or penetrating sealers
- - Sealers with fluorocarbon aliphatic resins
- - Sealers that are safe to use around food
Look for a sealant that’s designed especially for granite surfaces. These sealants are different than a sealant designed for natural stone. Because granite is so dense, the solvents and resins used in granite sealer need to be very lightweight.
The most effective granite sealants are usually called penetrating sealants or impregnators. These sealants contain a resin, a carrier and a solvent. They soak into the stone via channels in the surface.
By contrast, a surface sealer creates a hard barrier on top of the stone.
The resin used in granite sealer is critical to how well it works. Avoid linseed, silicon and siloxane resins. Instead, look for a fluorocarbon aliphatic resin. They’ll last longer than other resins, and they are more durable.
How to Seal Marble Countertops
What Not to Use
For marble countertops, there are also some ingredients you’ll need to avoid.
Avoid sealers with:
- - Sealants with citrus solvents or ingredients
- - Surface sealants
- - Linseed oil
Not all marble needs to be sealed. Before sealing a marble countertop, test it with mineral oil or water to make sure it really does need to be sealed.
Many people see etchings on marble, and they believe the stone needs to be sealed. Unfortunately, sealing marble won’t help to prevent etchings. Etching is not a stain. It’s actually a change in the chemical composition of the marble. This occurs when an acid comes into contact with calcium.
Marble is a porous, calcium-based rock that reacts with acid. When acidic items, like lemons, vinegar or even strawberries, come into contact with the marble, the acid and calcium interact to create these dull spots.
That’s why it’s particularly important to avoid sealers with acidic ingredients like citrus solvent. These will actually damage your counters.
Avoid linseed oil and tung oil as well. These will yellow over time, causing your once white marble to look old and dirty. Although linseed oil is often touted as a non-toxic, non-VOC sealant, marble is not the place to use it! Look for a non-toxic marble sealer instead.
What to Use for Sealing a Marble Countertop
- - Impregnators
- - Acid resistant sealers
- - Acid Resistant Coating – There are coatings on the market however most have a reputation of cracking, chipping, peeling and/or discoloring
The best sealants will be designed especially for the stone you’re sealing. Look for a penetrating sealer for marble. These are sometimes called marble and granite sealants.
If you’re sealing marble in the kitchen, we recommend that you look for a non-toxic marble sealer. These are sometimes labeled as “food safe” sealants. Avoid sealants that specify use for bathrooms and tiles, unless they specifically say “food safe.”
Honed marble tends to absorb more sealant than polished marble. And because marble is more porous than some other natural stones, this can make a big difference. If possible, find a sealer that’s designed for the appropriate finish your stone has.
What about water-based versus solvent-based sealants? Both will work on a marble surface, but the best choice depends on what you want to accomplish. Solvent-based sealants are better at repelling water. On the other hand, water-based sealants are better at repelling oil. Consider what types of activities you usually use the surface for, and choose the sealant accordingly.
When Not to Seal Natural Stone Countertops
There are some types of stone that don’t need to be sealed. Quartz counters, tables and kitchen islands fall into this category. Although quartz is made from natural stone, it’s combined with a resin in the engineering process. This resin means you won’t need to seal quartz. In fact, sealing quartz surfaces can actually leave them with a hazy film.
Some other types of natural stone don’t need to be sealed, either. Dense granites, for example, don’t always need sealing. In addition, sealing travertine, limestone as well as some marble is recommended more for cosmetic reasons than for protective ones.
Professional Sealing for Natural Stone Surfaces
Over time, the resins and solvents in natural stone sealer will break down. This means that they’ll need to be reapplied. Depending on the type of stone and its finish, sealants may need to be reapplied every year. Others may need to be reapplied every three to five years.
There are a few professional-grade sealants for natural stone that don’t need to be reapplied. We recommend Dry-Treat products, 3 in particular.
- - All natural stone products leave our shop sealed by us with a Dry-Treat product called Stain-Repella a penetrating, invisible and breathable water-based sealer. We offer a 15 year sealer by Dry-Treat called Stain-Proof or the 25 year sealer called Stain-Proof Plus for an additional charge.
- - For soapstone, the sealing is at the discretion of the home owner. They may go without sealing, use mineral oil, or we sell a product called Soapstone Enhancer from Green Mountain soapstone. Customers who want a lighter look go with nothing. Some like the stone darker so they put the Enhancer or mineral oil on the stone. This may need to be applied more often in the beginning to keep it dark if that is the customer’s preference.
In many cases, professional-grade sealants have warranties that assure they’ll protect your countertop for the advertised length of time. Having a professional apply these sealants is usually necessary to activate the warranty. If you’d like natural stone counters without needing to seal them regularly, consider having a professional apply a sealant like Dry-Treat Stain Proof. If you’re local to the Central PA region give us a call to apply your sealant!