You may have heard that there is no natural non-toxic sealer for real stone countertops. This is because most of the granite countertop slabs in North America are glossy or already come with a sealer. But if you choose the stone yourself, you can choose a slab that can be sealed with a natural and totally non-toxic sealer.
I tested all of the natural (as well as synthetic) stone sealers on many different stone types.
The testing went on for many months!
My top pick is definitely a walnut oil/wax mix which has long been used successfully on real stone. There are some caveats – there are some stones and some situations where this will not work well.
This all-natural, healthy, and food-safe “drying oil” works as an effective sealer for real stone and is usually the best choice for most applications. Drying oils polymerize, forming a durable finish on the surface.
Because stone countertops do need re-sealing fairly often, this becomes an area of priority to have something low tox.
There are some stones that would do better with one of the synthetic sealers. I will discuss those as well.
This post is not sponsored by any of the companies mentioned. All of the stone sealers I found that were candidates have affiliate programs, so all the links to the products here (the ones I liked and the ones that didn’t perform as well) are affiliate links. Upon purchase, I earn a small commission.
My Test Results – Walnut Oil Wins
I started by testing many different oils, waxes, as well as MetaCreme. I tested walnut oil (with wax), tung oil, hemp oil, and MetaCreme on a few different stone types. I tested dark marble, creme marble, slate, and later – white marble, grey limestone, and dark grey soapstone.
MetaCreme is a synthetic sealer, not a natural oil, but it is marketed as low odor and low-VOC. This is one alternative to the natural oils for those who are chemically sensitive or avoiding toxins. I tested two other synthetics low VOC sealers here (especially good for light-colored stones).
I also threw in OSMO oil and shellac for comparison because I had those around. (OSMO and shellac are not meant for countertops. Shellac might be used on stone but only in usual applications like artwork).
Oil Versus Water Based Sealers
I found that the “drying oils” – hemp, tung, and walnut all held up well as countertop sealers. They work best on dark or warm tones stones since they can yellow light-colored stones. However, thick oils like tung will not work over the long term as a second coat will not turn white.
Walnut oil is very light in odor, and is the all-round best natural sealer for stone countertops. It’s even more durable to stains and acids than the synthetic sealers.
Walnut oil repelled water perfectly. After a water test, none of the stones were left with a mark indicating that water had soaked in.
Resistance to Dye and Acid
I then thew mustard at all of them, both for the pigment and for the acidic vinegar in it, and left it on for a few short minutes.
The dark stones were all marred by the vinegar which broke through all of the finishes I tried.
The oil-finished stones were much easier to touch up. To fix those white spots all it took was adding a little oil and right away it looked back to normal. And because these oils are so safe to work with you can do that yourself with a small rag.
Synthetic stone sealers on the other hand are not easy to touch up after a vinegar spill. Those white spots were not fixed by adding another coat of Metacreme, so I was not as happy with the results.
I would pick walnut oil as my top choice for most stones, with some exceptions…
Which Stones Will Walnut Oil Seal?
Any honed stone can be sealed with walnut oil, though very light-colored stones can have some unwanted yellowing. This is the main drawback.
In my first round of testing, I was not happy with any of the natural drying oil finishes on white marble. It did work just fine on a creme colored marble pictured above.
On a light-colored grey limestone, it was iffy. Definitely test this out first if you are going with any light-colored stone including limestone – this might look totally fine or it might alter the color too much.
On really light stones that are white or cool tones, check out these three low-VOC synthetic options. Make sure to test the products if you are sensitive to chemicals, as you will be resealing the stone every few years or so.
Did the Oils Hold Up to Tougher Stains? (Plus More Oil Comparisons)
Walnut vs. Coconut vs. Jojoba
After I narrowed in on walnut oil as being the best all-around oil out of the first batch, I started another round of testing with lighter stones.
I also wanted to see if refined coconut oil could deliver the same results without any yellow or green color change.
I threw in Jojoba oil since that is a great finish on many natural surfaces like wood. (It turned out that worked much better on my skin and hair!)
Refined coconut oil is not a “drying oil”. Unlike walnut, hemp, and tung which polymerize forming a durable coating, coconut oil does not polymerize to form a topical coating. Using a formula with wax makes it a little more durable and it did succeed in not yellowing any of the stones, but it did not hold up very well when actually put to the test. And it won’t hold up for as long.
Light Grey, Dark Grey and White Stones
I tested two very similar samples of limestone that are cool-toned light grey, as well as white marble, slate, and dark grey soapstone.
Pure refined coconut oil can be used on soapstone and other stone counters that don’t truly need a sealer (as well as cutting boards), just keep in mind it does not polymerize to form a durable film. I also tried the version with wax.
I put them all to a serious test with palm oil. Coconut and jojoba certainly failed, with walnut oil offering the most protection.
Palm oil will be one of the hardest substances for natural oils to hold up to since it stains red and it’s an oil which other oils can’t hold up to.
Drawbacks to Walnut Oil as a Stone Sealer
The main drawback, once you choose a stone that is color compatible, is probably the time it takes a natural walnut oil finish to cure.
You should wait 5-7 days before using the surface, with a full 15 days before you start scrubbing it and using it to full capacity.
When it comes time to re-seal, simply add the oil in sections so that you can still use part of your countertops, or do it before going on vacation.
What is great about walnut oil is how safe it is to handle, even for most chemically sensitive folks. It does not have additives – you can get it on your skin and you don’t need respiratory protection. So touching it up should not be a daunting task. Just be sure to follow the instructions.
Which Countertops Can be Sealed with Natural Oil
Generally, any honed (not polished) stone that is porous enough to need a sealer can be sealed with the walnut oil/wax mix.
Marble, granite, soapstone, limestone, and slate can all be sealed with this oil.
Just test it for color change if it’s a white or light cool toned stone.
I can certainly see why this is sold as “Soapstone Sealer“, since it creates a perfect black finish on soapstone.
While mineral oil is the most common sealer for soapstone, it’s not totally non-toxic and benign. Walnut oil is just as good as a finish.
Paper Composite Counters
Walnut also works well on Richlite and Paperstone countertops. I tested it on that as well and was really happy that it left it looking quite natural. There was no noticeable color chance as these countertops only come in warm colors and dark colors.
It also allowed the Paperstone to retain its matte finish.
It’s a great alternative sealer to the other not as safe options used to seal paper composite countertops.
Walnut works well on wooden/butcher block countertops as well. Hemp oil also works well on wood, as the color change that happens with hemp looks natural on wood.
Concrete countertops can also be sealed with walnut oil or tung oil. Tung works better on concrete than stone because of how porous it is. On stone it forms too thick of a topical coating, making it hard to touch up.
If Stone is Sealed Already
To tell if the stone is sealed already, do a water test – put a big drop of water on the stone and see if the stone changes color. If the color does change then it is not sealed. If it does not change it is likely already sealed.
The walnut oil sealer can seal over an already sealed area. It’s not going to soak in or be quite as effective, but it will dry and polymerize. Also, it will need to be kept very thin so as to not build up too thick of a film.
My countertop post goes over stones that are dense enough to not require a sealer. So if water does not soak in, that can also indicate that it is one of these very dense stones. If you want to skip the whole sealing stage altogether, go with one of those stones.
Can You Use Hemp or Tung Oil on Stone?
I tried tung oil without thinning it and wiped off the excess. It worked just fine, but it may form too thick of a layer to be able to be touched up easily in the future.
If you put it on too thick it could also get frosty/gummy when used outside or go white when used inside. You might have to sand it down to fix it. And when you go to re-seal it you may have a problem if the first coat was too thick.
But because tung oil forms a thick more robust finish, if you want to seal a slate shower pan or an exterior stone, or exterior concrete like a birdbath – tung would work better and is more durable than walnut oil.
Tung oil can produce a more amber tone and that is another reason it won’t work on all stones. Even on a dark stone like soapstone, because it has a bluish hue, tung oil can make it look green. You will see this change immediately.
The Milk Paint tung oil is sourced from China and is amber-toned. I noticed this brand has a lighter odor than others I have tried (which I liked). Tung oil from South America can be more greenish.
Hemp oil as a stone sealer is not as tough of a finish but it can work well. I tried it and it did work in my experiments on stones where it is color compatible.
Walnut oil is usually the best choice for all stone countertops. The color change is very subtle and it’s easy to re-do and touch up without build-up.
Some may prefer hemp oil. If you have an allergy or aversion to walnut oil, hemp oil is the next natural oil to try.
But hemp oil has more of a hue to it than walnut oil and it can produce a greenish tone on light-colored stones. On white stone, you would see the color shift.
The color change will show up immediately, as opposed to yellowing over time says Dwayne, the owner of Real Milk Paint. On stones where I saw a color change to yellow, I did see it right away and it did also worsen a little bit over a few days or weeks.
Natural Sealers for Concrete Countertops
You can use tung on concrete floors as well, some folks have not had to redo them for 8 years or more. It provides a durable coating without making it slippery and slick.
Corinne Segura is a Building Biologist Practitioner with 8 years of experience helping others create healthy homes.
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