How To Tell if Granite is Sealed Properly
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:
Let me explain in more detail...
- Perform the water test for sealing granite countertops before applying a sealer to establish a baseline for the original "time-to-absorption".
- 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...
- Apply a second coat and test again after the second coat.
- Continue until time-to-absorption does not improve (increase) or is over 20 minutes.
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.
, 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.
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
Is Our Granite Sealed or Not?
(Canoga Park, CA)
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?
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