How To Tell if Granite is Sealed Properly

QUESTION:

We just had granite kitchen countertops installed and sealed, but are seeing dark water stains around the sink.


How do we know if the granite was properly sealed... or not?

ANSWER:

The only way to determine if granite has been sealed properly is to follow these steps:

  1. Perform the water test for sealing granite countertops before applying a sealer to establish a baseline for the original "time-to-absorption".

  2. After applying the first coat of sealer, test again noting the improvement (increase) in time-to-absorption. If time-to-absorption is over 20 minutes... you're done. If not...

  3. Apply a second coat and test again after the second coat.

  4. Continue until time-to-absorption does not improve (increase) or is over 20 minutes.

Let me explain in more detail...

Water should not absorb into a granite countertop if a sealer has been properly applied. At least it should not absorb quickly. This time will vary depending on the type/color of granite (more on this below).

Testing tells you how long it takes for water (which represents any liquid) to absorb into the stone. The sealer's job is to increase the time it takes for liquids to absorb.

Multiple coats may be needed. Testing also reveals how many coats are needed and when the granite has been completely sealed.

The time it takes should increase after each coat of a granite sealer is applied until a maximum time-to-absorption is reached.

You Know a Granite Countertop is Sealed When...


You know you are done when testing does not improve (increase) the time-to-absorption from the first to the second coat, or the second to the third, etc.

On average, when testing shows absorption takes 20 minutes or more (30 minutes is ideal) then the countertop/floor has been effectively "sealed".

This can occur after the first coat on many granite colors.

But hold on... this does not occur in every case. Some granites will not hit that 20-minute mark even when sealed properly with multiple coats.

Actual time to absorption (before and after sealing) is largely determined by the natural porosity of your particular granite countertop, which can vary a lot.

If your granite is more porous,
it will absorb liquids and stain quickly (i.e. white granite and lighter colors).

A sealer will increase this time, but it can only increase it so much. Multiple coats will be needed and maybe the best you can achieve is to increase the time to absorption to say 10 minutes (on a highly porous granite).

Now that can be a huge increase if the baseline rate of absorption started at 1 minute.

If a low-porosity granite (dark and black granites), liquids can take a long time to absorb. Sealing may not be necessary or only one coat is needed.

Very often with these dense, low-porosity granites, the natural baseline time to staining is 10 minutes, so a sealer may increase that time to 30 minutes or more.

It's easier to understand the above when you know how sealers work.

Sealers do not form a shell over the granite countertop. This is potentially bad for the stone.

What granite sealers do is dramatically slow down absorption so you have much more time to clean up any spills.

Stains can still occur if a liquid is left to sit on an effectively sealed surface for 20 minutes or more (depending on the quality of sealer, the quality of the granite sealer application, and the porosity of the stone).

But it takes a lot longer to absorb after sealing granite.

If you notice water quickly staining and darkening the stone even after a sealer was applied... well, it may be that the stone sealer was not applied effectively.

Simply putting a sealer on the countertop does not mean that it is sealed.

Proper sealer application requires:
  • Sufficient volume of sealer applied (thin coats don't work).

  • Sufficient dwell time to allow the sealer to completely absorb (without drying).

  • A sufficient number of coats to effectively seal the granite.
Tip: Never let the sealer dry on the surface. This does not help absorption but it does leave a hazy residue on the surface. Make sure to wipe off all excess and completely dry the surface after each coat (if 2+ coats are needed).

For complete information on granite sealers, applying sealers, etc. see the ebook All About Sealing Granite & Marble.

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removing dark stains on granite
by: K

I've read and tried baking soda, powder, vinegar....nothing works to pull up these stains. I think they are from water because... what else?
Is there anything to get rid of the large dark spots? Also, I'd seal after but want the stains out first. Thank you.

==== Countertop Specialty comment:

Not all stains are the same. You do need to use a poultice to draw out a granite stain, however, the ingredients needed depend on what stained the granite.

Unfortunately, there are many poultice recipes passed around online that are just useless.

For most stains it is much easier and more convenient to use a preformulated poultice like this Granite and Marble Poultice Stain Remover.

This product eliminates a lot of the guessing about how to make the correct poultice for your particular stain.
Dark Water Marks Around Sink
by: Anonymous

Hi, My granite has darkened around sink. I used a cleaner to draw out oils and water but still darker even after 2 treatments ( it did have some improvement).

My question is if I go ahead and seal it now, will it continue to dry out or stay dark because it is trapped under sealer?

==== Countertop Specialty comment:

Sealing a granite countertop will not trap any water in the countertop. It can still evaporate from underneath. Now, sealing a floor or wall tile can trap moisture in the stone because it only has the sealed surface exposed.

Water absorbing into granite around the sink is not a problem. It will darken the stone until it evaporates and then the darkness will disappear.

If this is occurring, then you should seal it because it is a sign that other colored or oily liquids could absorb and stain.

If the darkness does not go away, then something has absorbed and stained the granite.

In such cases, you would use a product like the Stain Remover Poultice.

It's best to remove all stains prior to sealing.
Help
by: Mary

My granite countertop is a year old and it's an ivory with brown flecks and a slight mossy green tinge to it.

I was told I needed to seal in a year, so I applied Dupont. I tested an area first and it looked like no change in color, so I went again and did the counters. I am just sick about this.

Part of the countertop stayed the same, and part has no green at all. So the effect is parts are much lighter than the other and it is very noticeable.

Also, I can't believe it was sealed very well, because some of the counters soaked up the sealant really fast, and other parts didn't soak in at all.

By the faucet, I have some discoloration, too, that never goes away.

I was wondering if maybe the company used a color enhanced sealant. Is there any way to fix this?

=== Answer:

Strip the sealer off the granite countertop using a solvent. Acetone may work, but you may need methylene chloride (found in paint strippers).

The fact that part absorbed quickly and the other didn't indicates that possibly only part of the countertop was sealed originally. It could be a difference in porosity of the slab, but not very likely to be so dramatic with the same color granite.

The change and difference in color after you applied a granite sealer is odd for sure. First, a standard impregnating sealer won't change the color or only very slightly darker... but it would/should do it uniformly.

If a color-enhancing sealer was previously applied (rare on a polished surface), then you would have see the color difference initially... not after applying your sealer.

I could be possible that the granite slabs used to make this countertop were originally a noticeably different color and an enhancer was used to match them... but this doesn't happen very often, so not likely.

Use the "Contact Us" form to email us and we can then request photos from you... but you need to email first.
Granite Finish
by: Anonymous

I have just had granite installed and the surface is grainy and pockey(small holes). It does not feel smooth at all.

I have had granite for years and this is the first time I have ever felt this "rough" texture on countertops.

Also, if anything is spilled/sits on the top it instantly turns darker and is discolored. Any idea what is wrong with this granite? Any ideas would be appreciated. Thank you.

==== Countertop Specialty reply:

First, it is rather porous and should be sealed. Some granite varieties are very dense, non-porous and do not need sealing. Others are very porous and need sealing.... maybe 2 or 3 coats even.

The gritty, pocked surface is likely a the sign of a poor-quality slab.

Granite is a natural product, so a wide range of quality (or desired characteristics) is possible even within the same color / name / variety.

Some granites will polish better than others. Meaning some "polished" granites will be shinier than others.

However, all granite that is installed should be smooth and free of excessive defects like pits. Grittiness is usually a slab that just can't be polished very well.

Now, such a slab should not be installed, but sometimes shady fabricators will pawn off these cheap, crappy slabs.

If you picked out the slab, then there's no one to blame. However, usually what happens in cases like this is you picked out a color or chose from a sample and this is the slab the fabricator used.

Particularly a problem with the "low-ball" fabricators that promise $25 sq. ft. install. Well, they can't make any money at that price without cutting a bunch of corners.

Unfortunately, there likely isn't much hope for the graininess of your countertop, except maybe a chemical coating, which is not something you'd normally want to do.

The pits can be filled using the Marble & Granite Repair Kit for Chips/Pits.

But I would have a reputable fabricator or stone restoration contractor take a look to be sure of the cause and any possible solution.

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Is Our Granite Sealed or Not?

by Mara
(Canoga Park, CA)

QUESTION:

We just got the granite countertops installed in both our kitchen and all the bathrooms. The color is on the light side, beige/cream color.

We place anything wet on it and the counter top will show the water stain.

I asked the contractor if it has been sealed and he said, "of course. It wouldn't be shiny if it wasn't."

I told him what I've been reading online including the paper towel test. He says that it's normal for granite to get wet and show the stain. As long as it dries up quickly, it's fine. All granite is like that.

Is my contractor telling me the truth? Or is he just trying to get away with not having to seal it properly?

ANSWER:

Your contractor is not telling you the truth, but he may not know the truth.

"It wouldn't be shiny if it wasn't sealed."

Total BS... the shine has nothing to do with sealing. The shine is produced at the factory with high-friction industrial machines.

He says that it's "normal for granite to get wet and show the stain. As long as it dries up quickly, it's fine. All granite is like that."

Yeah... many granites (not all) are porous and will absorb water and show the stain, but that is precisely why you need to seal it. Water will dry up and won't leave a stain, but coffee, wine, oil or anything else that has a chance to absorb will stain.

If it were sealed properly, the water would not absorb at all.... well, not rapidly anyway. It would just bead up or form a puddle without any color change like a stain.

However, if a liquid is left on most granite for 30 minutes or more it could potentially abosrb (even when sealed) depending on the original porosity of the granite.

This is because granite and marble sealers greatly reduce or limit absorption, so it takes a lot longer... but they do not absolutely prevent it.

Usually water (and most liquids except oil) evaporate before absorbing into a well-sealed countertop.

The fact that the water is "staining" (if under 10 minutes) is the exact indicator that no granite sealer has been applied (or applied very poorly) and the countertop needs sealing.

If sealing is supposed to be included in the job, then I'd ask him what the charge for sealing is and deduct that from the total for final payment.

Tell him you'll seal it yourself. It isn't hard to do correctly.

If you choose to do this, I'd suggest using these recommended marble & granite sealers.

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granite in shower darker from glue stains
by: Laura

We are in the process of having a full bathroom reno and we will be installing a granite countertop on our vanity, for the sill in the shower and on the bottom of our shower niche.

The granite on the sill and the niche were glued down yesterday and the color of the granite looks totally different.....the color is supposed to look a creamy beige with some brown flecks and now it looks as though it has a darker section throughout the area that was glued down.

Is this as a result of the glue and water absorption and will it return to normal once it dries? Will this also happen when the countertop is installed?

==== Countertop Specialty comment:

Glue stains can occur during installation with certain combinations of glues and granites.

Sometimes these will go away as the glue cures. However, they can last a long time and can even be permanent.

Granite installation adhesive stains can often be removed, but it is difficult. The glue can continue to leach through the granite feeding the stain.

I would reserves final payment until the stains go away. If they persist beyond a few weeks, then follow DIY procedure in the Removing granite stains e-book for removal.

Also, I'd question the installer about the glues and additives used. Additives to decrease cure time are often at fault. Certainly, you'll want to avoid the same problem on the granite countertop.

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