How to Clean Slate and Shell Go Stones

I’ve sold Go stones for over three years now and people often ask me how to clean and take care of a set.  I finally decided to put together this little guide in hope it’ll help you keep your set looking nice for generations.

A little disclaimer first.  I haven’t spent much time editing or polishing the language, so my apologies for poor grammar or drab speech.  🙂


I’m selling Go equipment on Ebay again starting the final weekend of September.  Because ebay has a limit on free listings, I rotate sets each week, so if you saw something you liked and it didn’t sell, but isn’t posted the next week, please contact me and I’ll be happy to make arrangements for you.




For Slate and Shell, the best way to keep your Go stones looking nice is to wash your hands before your play.  This removes excess oils and dirt from your hands.  When finished playing, take a white cloth and wipe each shell stone to remove excess hand oil.

Follow this simple step and it’ll be years before your sets will need cleaning.

Step 1: Determine kind of stones you have.

The most important thing in cleaning Go stones is knowing what kind you have.  For those who bought Slate and Shell from Mr. Kuroki or something else from another company, you’ll likely know.  If you bought your set from Ebay though, it you might have trouble identifying the kind of stones inf your set.  Slate and Shell, Yunzi, Glass, Jade, Agate, Ing, Plastic or something else.  There are many possibilities.

For demonstration purposes I’ll concentrate on Slate and Shell.  These are what I specialize in.  However, if you have something else, just follow Step 2 below and that should be sufficient.

So, you have some white and black stones but don’t know if they’re glass, yunzi or slate and shell.  You can determine what you have through fairly simple observation.

If the white stones have grain (lines) running through them, then you have Shell stones.  The grain may be strait, slightly curved, heavily curved or wrapping the stone.  The grain will appear on only one side in less your stones are from a giant clam…such sets are extremely rare.  If you have trouble seeing the grain, shine a bright light behind the stones to be sure.

As an added note, Clamshell stones are note bright white.  They have an eggshell/ivory color in contrast to glass or yunzi.

Black stones are a little more difficult.

Slate traditionally accompanies clamshell, but oft times, when buying a used set, you’ll find some glass stones replacing lost or broken slate.

If there’s sparkling in any chips or nicks on the stones, then you have glass.

If you can shine a bright light behind the stone and see a greenish hue, then you have Yunzi.

If you’re still not sure.  Dump the black stones into a bowl of water.  The Slate will appear matte black while glass will be bright.


I’ll use the above stones for demonstration purposes.  They’re from a sized 25 standard grade.  You’ll notice the yellowing.

Yellowing is the result of extensive play and poor care.  It happens when oils from your fingers seep into the stones over years of use.  Surface yellowing like this can be cleaned and the stones will look like new, but once it works too deep into the stone you can diminish it, but it’ll be impossible to remove completely.

Sometimes you’ll see stones that have browned rather than yellowed.  Browning is caused by tobacco smoke.  Avoid smoking anywhere around Go equipment.  Tobacco smoke will wreck havoc not just on stones, but bowls and boards as well.

Step 2: Soaking

DSCN7284 DSCN7288

To begin the cleaning process, soak the stones in water with a mild detergent for at least an hour.  This will loosen surface dirt and remove hand oils.

As a side note, you’ll notice I’m using a glass bowl to clean the stones.  I actually don’t recommend this.  Shell stones (especially standard grade) have a tendency to chip, so I recommend a plastic bowl instead.

For the same reason, you may want to wash slate separately from shell.  This is a case of do as I say and not as I do 🙂


Okay, the stones are clean and now you need to rinse them.  The bathtub is a good place.  Again, shell stones are prone to chipping so use some kind of cushion.  Here I’m using a…well…I don’t know what that blue thing is but it works 🙂

Turn on the water and let it cover the stones completely.  Make sure the water is lukewarm or cold.  Never use hot water on shell stones.

By letting the water cover the stones you’re making sure all the detergent is removed.

Now pick up the stones a handful at a time, swish them in the water for good measure and lay them out on a towel to dry.


The ten stones I’m using for a demonstration are at the bottom.

Don’t worry if you have hard water and it leaves residue, we’ll take care of this problem at a later step.

If you do not have slate and shell stones, then just take a white cloth, dry the stones thoroughly and now they’re ready to play.  Alternately, you can let them dry, then take a cloth and wipe the hard water deposits off.

Step 3: Hydrogen Peroxide = H2O2 (Shell stones only)(Skipable)

This step is for Shell stones only.  If you soaked slate, glass, or anything else in H2O2 it won’t hurt, but you’re going to be wasting your time.

Once you’ve cleaned your white stones, you need to decide whether or not you’re going to clean them again, this time with Hydrogen Peroxide (H2O2).  If your stones are yellow, brown, or old and orange, then the answer is likely yes.


Here we have the demonstration stones after their initial cleaning.  You’ll notice how shell has some yellowing.  It isn’t bad, but does detract from the beauty.

Yellowing like this is the result of oil and dirt working its way into the grain.  Hydrogen Peroxide will remove, or at least mute this discoloration.

If the discoloration goes too deep it’s impossible to remove, though you can still improve the look of the stone with H2O2.

DO NOT USE BLEACH!!!  You’ll ruin your stones if you do


In the picture you have 3% hydrogen peroxide, available in just about any supermarket, and 35% food grade hydrogen peroxide found in specialty stores only (or online).   I use 35% to clean the stones I sell, but it’s expensive, especially if you’re only working on a single set.  3% will do the same job, but it’ll take longer.

Since you’ll likely use 3%, that’s that I’ll utilize for demonstration purposes.

If you choose the specialty 35%, make sure you get food grade and not sauna and spa.  A note of caution…this stuff is strong.  Use rubber gloves and do not get any on your body.  It’ll cause your skin to turn bright white and bubble under the surface.  The effect only lasts for a few hours, but really stings!  I speak from experience, and you have been warned.


Place the stones in a plastic cup (again to avoid chipping) and fill the cup with hydrogen peroxide.

At 35% I let the stones soak for 24 hours, with 3% you’ll want to leave them longer.  For my demonstration I soaked the stones in 3% for 48 hours.

Once finished, thoroughly rinse the stones with water.

Make sure the stones are completely rinsed.  This is EXTREMELY important.  If you don’t take care with this step and let the H2O2 dry on the stones, then you risk ruining them, especially if using 35%.  The Hydrogen peroxide may burn through the wax finish while drying and make puffy white spots in the stones which won’t come out.  While the stones are soaking, there is no danger, but once you remove them, make sure you rinse them.

Once rinsed, spread the stones out in the sun or a well ventilated space to dry.  Make sure not to leave them in the sun for too long (short stays of a day or two won’t hurt them though)


Here you see the demonstration stones after they’re H2O2 bath.  There is still some yellowing, but they look much, much nicer than before.

Since this set wasn’t an extreme example, I wanted to show just how effective Hydrogen Peroxide can be.


These are sized 34 stones I removed from a set to which they didn’t belong.  This is an example of extreme yellowing, brought on by years of poor care and neglect.


Here’s the same set of stones after 48 hours in 3% Hydrogen Peroxide.  The difference is remarkable.  This set will never be pristine white again, but the yellow gunk is gone and the stones are much more pleasant to look at.

UPDATE – APRIL 2016 –> Through some consultation with manufacturers I’ve learned that additional 24 – 48 hour periods of soaking (5 – 6 times in total) will further whiten the stones. They must first be dried (as listed above) before subsequent soaks.

My experimentation on some yellowed sets have shown promising results.  The first soak will definitely create the most drastic change, but further uses will help improve the color.

This still won’t cure extreme yellowing (like seen above), but it will help.

Step 4: Waxing (Shell Stones Only)

Waxing the shell stones is potentially the most time consuming step.  There are a couple of options for you.


The best wax is Ibotarou イボタロウ.

Ibotarou is an insect wax used in China and Japan.  It works wonders on Go stones. It’s devilishly difficult to find here in the U.S. and outrageously expensive to buy on Rakuten or Yahoo Auctions Japan.  You’ll usually find it in 30g packets for $10+.  Make sure to get the powder, not the bars.

Take the powder, dump it in a plastic bag with your stones.  Shake it around and then wipe each individual stone with a cotton cloth.

As an alternative, I use carnauba car wax.  Sounds odd, but it works extremely well.  Make sure you get wax without any additives…the purer the better.


The top wax is cheap and does an excellent job.  The bottom is the best I’ve found, and I save it for special sets because it runs between $20 and $30

You can find both on

Waxing the stones serves two purposes.  First, if you have hard water (like I do) it gets rid of the residue.  Second, it makes the stones shine like (or almost like) new.


To begin, take a small dab of wax and rub it in the corner of a cotton cloth.  (You may need to repeat this several times as you work)  Then take your stones, one by one, and rub the wax around them.  You only need to use a light coating, it doesn’t take much.  Once finished, set the stone aside and move on to the next one.  Expect to take at least an hour if you’re working on a full 180 stone set.


Here you see the demonstration stones.  Once you’ve finished with the set, spread the stones out and let them sit until the wax is just barely dry, thirty minutes to an hour tops.  Do not let them sit any longer or the wax will become too hard and very difficult to remove.  If it becomes too hard, just re-wax the stone(s) and wait again.

Once you feel the stones are ready, take a white cotton cloth and thoroughly wipe each piece clean.  Step back and see how they shine 🙂


Here are the finished shell stones.  Nice and shiny and ready to play.

Step 5: Oiling Slate Stones

Now we come back to the humble slate.


Once you’ve finished drying the slate stones, they may look something like this.  A little drab and lacking in luster.  Many players prefer their slate stones like this and if you’re one of them, then you can skip this step.

You will need some good mineral oil.

Oiling the stones isn’t difficult, but it is time consuming.  There are two ways to go about it.

The first method is to place your slate stones in a plastic bag, add a few drops and shake it a round.  Once finished, take a disposable cotton cloth and wipe the stones down one by one.  I recommend wiping them two or  even three times just to be safe.  You don’t want mineral oil getting into an expensive board or onto your shell stones.

The second method takes longer, but I prefer it.


Take a white cotton cloth and drip five – ten drops of the oil into one of the corners.  Take each individual stone and rub it around.  Once done, set it aside and repeat.


Once you’ve finished oiling the stones, you’ll need to wipe them down.  Take a cotton cloth and remove the oil from each stone, one by one.  This won’t remove the oil entirely, so you’re going to need to repeat this process another two times.  Even if the stones haven’t been cleaned for over a century, once finished, they’ll have a new luster.


End result of cleaning slate stones.

What To Do With Older Sets

Through use and natural aging, Go stones take on a beautiful ivory appearance and feel.  These sets are old, often from the late Meiji, Taisho, or early Showa eras.  They usually consist of very thin (less than size 20) stones.

Sets this old are almost exclusively native Japanese suwabute clamshell (often called Hyuga Clamshell).  You’ll often come across these venerable sets on Ebay or Yahoo Auctions Japan and more often than not, they’re in terrible shape from decades of abuse.

You can clean these sets, and while they’ll never look new again, they can be made to look beautiful nonetheless.


The stones above are from one such set.  They don’t appear to have been been cleaned in more than fifty years.  Grime cakes the surface.

The first step is soak the stones in a mild detergent, just like normal cleaning.  Let them soak for at least three hours, longer is better.  This will loosen the grime.  Next take a fingernail cleaner like the one pictured above, and brush each individual stone to remove the excess dirt.


Once scrubbed, the stones look much nicer, don’t they?  Unfortunately oil and dirt has worked so deeply into them that you’ll never get it out.  It’s impossible.  Not even Mr. Kuroki with all of his equipment could do it.  You can dampen the effect though by following step #3


After their H2O2 bath, the stones are much nicer.  The harsh, gunky orange is now much more pleasant to look at and in four of the cases above the stones have whitened significantly.

At this step I recommend buffing each individual stone with a fingernail brush, like the one pictured above.  Many stones this old are chipped or uneven and the buffing helps ease the harshness of the edges.


Finally wax the stones and they’ll have a beautiful shine like the ones pictured above.


Here you see the difference between the ten cleaned stones (pictured top) and ten stones from the same set that haven’t been cleaned (pictured bottom).

In Closing

Wash your hands before a game, wipe the stones afterward and clean them as needed.  If you take good care of your Go stones, they can last generations.

For those interested, I’ll be happy to offer a Go Stone cleaning service.  Please contact me on the 19×19 forums for pricing quotes.  My username there is Erythen.

Alternatively, if you don’t mind international shipping and would like a truly exquisite service, Mr. Kuroki, the finest Go Stone manufacturer in Japan, offers a professional service.  Contact him for details.


Here’s a site in Japanese demonstrating a cleaning with H2O2 you may find interesting.