Sealing synthetic waterstones

TLDR: I'm thinking about coating various waterstones in spar urethane. In some cases to protect the stones long-term, and in other cases in an attempt to diminish their water consumption in use. Thoughts are welcome.

After acquiring a few low- and mid-range (400, 1000, 3000) Naniwa Chosera stones -- which have indeed been very nice so far -- I have been holding off on the higher grits because of accounts of cracking, crazing and crumbling I've seen around. That is, I had been holding off on the higher grits... until I found a sweet deal on an 8k Snow White which I couldn't resist. Which leads me to the question of sealing synthetic waterstones to protect them from long-term damage.

I have seen both cashew lacquer and epoxy recommended here and there for sealing; but both of those would be more -- expense and trouble -- than I really want to spend on this endeavor. So, at least for the time being, I plan on using some spar urethane which I have and am experimenting with already -- mainly because it was available and quite cheap. And I'll use it up for outdoor wood projects either way...

To start with, I am sealing 5 sides of a Naniwa dressing stone (the kind included with the Choseras) to see how it behaves, and how it holds up to prolonged exposure to water. If that works out well after curing, I am thinking about sealing up a King Deluxe 1000 which I think could benefit from being less thirsty, despite the fact that I already permasoak it. Same goes for a 220 grit "Pink Brick" I recently acquired and is a thirsty beast. I figure that whatever exposure to water the splash-&-go Choseras get would be light-duty compared to the soakers, so the King and company should be a decent test to see how the urethane holds up.

Beyond wondering about how the sealant will perform with water, I am also concerned about how the oil-based spar urethane might react with the magnesia-based Naniwas. I believe both the Naniwa dressing stone and the King Deluxe are clay binders which should be quite resilient to being exposed to sundry substances -- not sure about Pinky, though. On the other hand, the magnesia-bound Naniwas seem to demand kid gloves for small things like soaking and drying; so coating them in oil-based sealant is of some concern.

Any thoughts about this last point would be most welcome, although input of any sort could prove helpful.

I see no benefit to sealing synthetics and it might cause damage due to differing rates of expansion and contraction during wetting and drying. This is strictly speculation on my part as I've never tried it.

One of the main selling points of spar urethane is it's ability of expand and contract with temperature changes when used in its intended role as an outside wood finish. I am hence hopeful that this aspect shouldn't pose issue.

Setting aside the non magnesia-binder stones I mentioned in my post, the main objective of this endeavor is to have the Snow White only absorb water from the work surface on top. It has been my observation that when sharpening on my 1k Chosera, water gets everywhere, top, sides and around the base on the stand; and then when I slowly dry it, it dries somewhat unevenly. I dry it and the 3000 upside down to avoid having water linger around the base and soak the stone longer than necessary, and the water that soaks in during the sharpening slowly percolates out through the top.

I feel that this could be improved upon if I can seal all the non-working sides of the stones: then water will only absorb into the surface which I am most often going to lap off in due course regardless, and, seing as how it will only enter the stone through the top, when I turn it over for drying presumably the water will drip out from the unsealed top and drying will happen evenly across that face while being prevented from happening quickly from the sides by the sealant.

I am finding that I would have a harder time still justifying my HAD if these somewhat expensive high-grit stones -- which should last me at least a decade, if not more -- start cracking and crazing in a year or two...

I would worry about sealing 5 sides, because water that penetrates into the bottom of the stone would have no easy way out. Then again, maybe that would cause a slower and more even drying process... It will also be interesting to see what it's like honing on top of a pool of water... It will be an interesting experiment.

That was exactly my concern. If water only can enter on the top it will soak into the hone more there than in other areas. Some hones do swell slightly. Having only one point of entry and egress for the water might cause internal stress.

Occam please let us know how it goes if you give it a try.

Quote:

---

Originally Posted by holli4pirating

[...] that penetrates into the bottom [...]

---

heh heh heh.

Quote:

---

Originally Posted by Utopian

[...] If water only can enter on the top it will soak into the hone more there than in other areas. Some hones do swell slightly. Having only one point of entry and egress for the water might cause internal stress. [...]

---

This is a something I've wondered about, yes. That said, I'm already using Choseras which come attached to bases; so by necessity there's always some parts which get wetter than others (heh).

When using them, I just spray the top with a little water, let that soak in for a minute or two to improve the feeling of the hone and then add a little more water as needed. In fact, doing it this way, I notice that the edges of the hone need more water sooner than the middle. These Naniwas aren't very thirsty at all, so I assume that water doesn't soak in very deep, but it does seem to get drawn into the edges more readily.

Which is to say that: (a) I'm already wetting various sections of the stone differently -- particularly if one also considers the deeper parts of the stone which I guess never get any water, assuming no prolonged soaking -- so that differential expansion/contraction is presumably already happening now, and that won't change much if I seal the underside and the sides, I don't think; and (b) given that the edges of the top already dry out a little faster than the middle, I actually imagine that sealing the sides could make the entire top face act more uniformly with regards to water absorption.

But these are just some of my observations based on limited usage, what I hypothesize could explain them, and what I imagine might happen if I apply some sealant to the hones. I'll be sure to post back with results if I go ahead with the more expensive magnesia waterstones.

As far the King stone is concerned, it won't be subjected to repeated wet/dry cycles if all goes to plan, given that it usually just resides in water all the time. I imagine that if I seal it on 5 sides when it's dry, then water will just soak in from the open side, puddle inside it when in use, and just kind of stay there when it goes back in the bucket -- Assuming the urethane holds up to underwater use, which isn't obvious to me at this point.

However, this talk of expansion and contraction of hones in relation to their water content has got me wondering, and I think that I will take a couple of measurements of Kings in both their dry and soaked states, just for fun. It would be more interesting to perform a similar test on a magnesia Naniwa, but I don't want to soak one for any prolonged period of time.

In the meantime, I have a needlessly glossy dressing stone in need of further curing before I try dunking it in water...
https://i.imgur.com/BKb09iqb.jpg

I've only ever sealed one synth, though Max at JNS recommends sealing all stones natural or synth. The Shapton Pros appear to be sealed on the sides (and on the back for the old ones and Kuromaku) with something like tile sealer or what the Japanese called 'Hone Coat'.

Once I tried sealing a large Suehiro 1k - basically a King 1k - with lacquer to do what you mentioned, reduce water absorption. It failed miserably. However, it dried out in about the same time, many days lol, so I don't think there's any risk of water staying in a hone that you'd perma-soak anyway.

I definitely wouldn't seal a stone that I perma-soaked, I'd doubt that the coating would stay on over time and I don't understand what you'd accomplish by coating a perma-soaked stone.

Cheers, Steve

Hey, Steve56! It is actually some of your posts about sealing a Snow White, and it then doing well -- whereas one of your acquaintances went through several (4, I think?) hones which all had cracking problems -- which got me on this kick.

Quote:

---

Originally Posted by Steve56

[...] Once I tried sealing a large Suehiro 1k - basically a King 1k - with lacquer to do what you mentioned, reduce water absorption. It failed miserably. [...]

---

Could you expound on what about it failed miserably? I am rather curious, for obvious reasons.

Quote:

---

Originally Posted by Steve56

[...] I definitely wouldn't seal a stone that I perma-soaked, I'd doubt that the coating would stay on over time and I don't understand what you'd accomplish by coating a perma-soaked stone. [...]

---

Yes, the durability of the coating when immersed in water is an open question. Really though, I am using the soakers as more of a test to see how well the urethane will hold up before slathering it onto the Snow White which should be a much easier proposition for the sealant to handle, long term.
But, I am also curious to see if maybe I can turn the King into a kind of "perma-wet" stone; that seems like it would be interesting also -- in the somewhat unlikely scenario that the urethane coating proves both watertight and resistant to perpetual contact with water... And as for the 220 pink brick -- that thing is, in my admittedly limited experience with waterstones, the first time I am getting frustrated with how thirsty a stone is; no soaking for any length of time gets it to hold any significant amount of water on top; I can work up a mud which then holds a little water, but doing so wears the stone faster than I need to, and also limits me to grinding on said mud, which is slower than light pressure on the stone with no mud, and therefore not necessarily how I would prefer to use the stone in all cases. Hence, I'd get more use out of Pinky if I could finagle some way for it to hold more water near its surface and not just pass it straight through like nickel beer.

Hey Occamstrop!

The Suehiro coat failed because it absorbed just as much water as before and took just as long to dry.

The Snow White failed too, just not with me. It never cracked on me with or without the coating, but after coating and using it for a while, I sent it to a friend in Lake City, FL who had been through 4. Sure enough, after a while he notices fine spiderweb cracks on the surface which is how all 4 of his began failing.

I don't know what the difference/cause is. My first thought was water, but we both use distilled water to hone with. Humidity maybe?

The idea to coat the Snow White came from the Shapton Kuromaku/Pros that also once had a cracking problem in the Westen US. Allegedly they reformulated the stones, but the Pros also appear to be coated on the sides (they're 2-sided now) and the Kuromakus on the sides and graphics side. So I decided to try coating the sides and back of the SW then send it to my pal as an 'acid test'. Oh well, sometimes you eat the bear and sometimes the bear eats you...

Cheers, Steve

I've sealed my 1k & 3k Choseras and my 5k Chosera, that I purchased used, came to me sealed. I live in dry Colorado. I don't think the sealing had any effect on the checking. My 3k was checked when I got it and seems to have healed itself. The 5k checked after I got it, but I think that is just the nature of the stone.

Keep in mind that sealing can lead to mould if the water cannot evaporate.

5 years and a full set of Naniwas and no sealing , with not a problem a one,, I do like Glen, soak for a few while using the preceding stone, set down for a few minutes so any thing that needs to normalizes, then my DMT for 3-4 figure 8,s to some slurry going then get after it. like I said no problems, and my 5k and the 8k snow white shoed those spider webs or crazing, yet has had no effect on its ability to hone smoothly. Tc

Quote:

---

Originally Posted by tcrideshd

[...] like I said no problems, and my 5k and the 8k snow white shoed those spider webs or crazing, yet has had no effect on its ability to hone smoothly. Tc

---

Did the spider webs or crazing occur on the tops of the 5K & 8K? And if so, did the light lapping with the DMT completely remove it before use? Or did they hone smoothly, as you say, despite being crazed on the surface even after the lapping?

With an 8k, TC would have the SuperStone, aka Specialty, Naniwa hones. I never have heard of any crazing issues with them, but they certainly can swell/shrink due to moisture.

The crazing problem is with the higher grit Choseras, aka Professional, hones. As far as I know it affects the 5k the most and lesser so with the 10k.

HERE is a thread I started a long time ago about the variable swelling in the SuperStones. Some swell more in the middle and some more in the ends. The take home lesson was to deal with the water exposure consistently for consistent results.

Occam are you considering the Pro or Specialty hones?

edit: I should thank you for that thread, btw. It's a very helpful discussion of this topic I came across once I realized that maybe I wasn't imagining that my thin 12K hone was shapeshifting on me between lappings...

I mean, tcrideshd does mention it being an 8K Snow White, right? That thing is magnesia-based, like the Choseras and sufficiently high-grit to be pertinent, being between the 5K and 10K Choseras, which are the main culprits in the crazing/cracking conversation. Also, like I said, an 8K Snow White is what got me seriously thinking about this in the first place. I just assumed the 5K Naniwa referenced with regards to spider webs was a Chosera/Professional...

I've never heard of any problems with the Superstones and their ilk cracking or anything of the sort -- although i do have a thread going about soaking them. And to your point, the reason I am interested in soaking them is that it would be one way to be sure to have them consistently wet in an easily repeatable fashion. I suspect that no harm would come to them if I tried permasoaking them, but I am too chicken to try it for the time being.

I currently own or am thinking about acquiring most of the Chosera/Pro stones up to 5k and I have both the 10K and 12K 20mm Superstones (literally Superstones; my 10K is the based model, 12K is without base) and also a 10mm thick Kagayaki 12k (which is the most recent incarnation of the Naniwa 12k, AFAIK), which seems to be a slightly different shape every time I look at it...

Quote:

---

Originally Posted by Occamsstrop

Did the spider webs or crazing occur on the tops of the 5K & 8K? And if so, did the light lapping with the DMT completely remove it before use? Or did they hone smoothly, as you say, despite being crazed on the surface even after the lapping?

---

Speaking for my 5k Chosera. The crazing is on the hone surface and does remain after lapping. I always at least give the surface a rub with the Naniwa rub stone to make sure that there are no steps in the surface, which can sometimes be felt with a fingernail when the stone is dry before use.

Quote:

---

Originally Posted by Occamsstrop

I mean, tcrideshd does mention it being an 8K Snow White, right? That thing is magnesia-based, like the Choseras and sufficiently high-grit to be pertinent, being between the 5K and 10K Choseras, which are the main culprits in the crazing/cracking conversation. Also, like I said, an 8K Snow White is what got me seriously thinking about this in the first place. I just assumed the 5K Naniwa referenced with regards to spider webs was a Chosera/Professional...

---

Yup, sorry to say I totally forgot that the snow white was part of the discussion.

they honed smooth with the crazing still there I haven't tried to lap it out,, there was a disscusion on this a while back the only issue was it just wasn't pretty enough for some, the performance was not affected. as was said, I don't see the benefit of sealing these stones. it seems quite a bit of sealing is done for purposes of retaining the provenance of the stone, not protection,, I mean hell, naturals were subjected to a lot more torture than we give them and synthetics,, I,m sorry but most people use both sides, so sealing would lose some stone in my mind.

But hey , I say do what you want with your property. just know that I haven't had any issues nor has any of the guys I deal with or know in this honing world. Tc

myself I wouldn't permasoak the naniwas,, King yes naniwa no

The crazing on my Chosera 5k was bad enough to occasionally need lapping. Otherwise, as Bluesman pointed out, sometimes the edge of one of the regions would stick up high enough to catch a blade slightly.

TLDR: Yes, I am aware of how much of a waste of time this all is, arguably. No need to harp on it. *shrug* That said...

***

After an extra week's worth of curing time, my Naniwa dressing stone has now been submerged for half again as long. The spar urethane has only held up very satisfactorily in areas where the coats went on thin and drip-free.
Here's a couple of [poor quality] pictures of how it's looking:

http://i.imgur.com/tyIF08T.jpghttps://i.imgur.com/tyIF08Tb.jpg
This (#4) is the best side, it was brushed on while vertical but with thin coats so there were no big drips. Except for the bright white line (which was at the bottom originally) where it sagged all around, and never fully hardened before soaking, presumably because of excessive thickness.
http://i.imgur.com/W2Sibxt.jpghttps://i.imgur.com/W2Sibxtb.jpg
This side (#2) has some drips which have turned white after the soak, it also has the same white line.

http://i.imgur.com/AEfCoA0.jpghttps://i.imgur.com/AEfCoA0b.jpg
This (#5) was the top of the stone when I applied the urethane. Before soaking, it was the nicest looking side, but most of it has turned milky now. I believe that coating it while flat allowed too thick of a layer to be built up, which didn't cure as well as the sides; at least not with the curing time I was allowing between applications, based on the directions on the can.

https://i.imgur.com/BPMZHHmb.jpg
Once saturated, the stone only very slightly absorbs extra water added to it. A few drops of water can stay on top for several minutes; this picture is taken after 5 minutes have elapsed. It does eventually soak in after 10 or so minutes. This stone's usual behavior with regards to water intake is similar to my King Deluxes, so there definitely is a marked difference.

***

I have taken a few measurements throughout, mainly as a reference point for other stones which I plan on messing with later...

I measured the dry, coated stone as:
L:2.660" x W:1.334" x H:1.948", 225g

After 12 hours soak, I measured:
L:2.664" x W:1.335" x H:1.945", 259g

After 8 days soak, I measured:
L:2.659" x W:1.334" x H:1.945", 258g

The length measurements are as close to being unchanging as my limited accuracy can vouch for. In fact, I am somewhat surprised that my readings came out so closely grouped. The weight measurement is practically identical between the two later measurements, the difference almost certainly being due to manipulation.

***

I am concluding from this that there is a decent chance for improving my results with the spar urethane if I apply thinner coats and make sure to avoid drips and sagging -- no big surprise there, really. I am pleasantly surprised at how well the sealant appears to be holding up in areas where the application was luckily better executed. I am also satisfied that this yields an exterior layer of sealant which does appear to function as a water tight shell. Finally, the measurements look to set a baseline for how much, or how little a stone expands when thoroughly soaked.

Now, moving on to my King Deluxe 1000...

Gents I've read your input and while I understand your views, I would NOT seal my synthetic water stones. Bruno has stated one very important reason. Mould! I have sealed my natural stones but prefer to leave the synths naked. So far that choice has worked out well.

Quote:

---

Originally Posted by BanjoTom

Gents I've read your input and while I understand your views, I would NOT seal my synthetic water stones. Bruno has stated one very important reason. Mould! I have sealed my natural stones but prefer to leave the synths naked. So far that choice has worked out well.

---

It isn't a completely irrational consideration. Does anyone have experience of a sealed synthetic become moldier than it otherwise might've? Is it a common problem with naturals?

Or is this just a purely hypothetical problem which could just as easily be solved with a cap-full of hypothetical bleach?

I’m less than a year into honing, so excuse me if this dumb question. My concern about sealing a synthetic is — what if I want to use the other side some day?

I’ve already done that with my 1k for when I’ve breadknifed a blade, hone a Gold Dollar, or otherwise need to treat the stone roughly. Then flipped it to the primary side for final bevel set.

Or, suppose I chip an edge or corner on the primary side.

Quote:

---

Originally Posted by MrHouston

My concern about sealing a synthetic is — what if I want to use the other side some day? .

---

Your going to lap the new side anyway before you use it. I predict the sealing medium to be gone in 3-2-1____

Quote:

---

Originally Posted by MrHouston

[...] what if I want to use the other side some day?

---

Wanting to use the other side is a consideration, but given that I usually only hone on a flat surface, I don't miss having a second side because it would just mean letting two sides go out of flat before lapping. But that's just how I use mine.

I suppose that if I maintained more convex grinds, I could want to have one curved side, and one flat. Or if I purposefully groomed one side of a high-grit stone to have deeper scratch patterns than the other, more refined side -- that too, I guess. And maybe if I kept one side rigorously flat for razors, chisels and plane irons, and used the other, irregular side for knives and rough work, somewhat like you describe. etc... Honestly, my own main reservation is that once in a blue moon I use a 1 inch-wide side on some thicker hones for something; that wouldn't work with having 5 sides sealed either...

Still, I have several thick 1000-ish King stones which I could use; so I won't miss being able to turn one on its side if this works.

More importantly, as concerns the more "delicate" magnesia-based synthetics like the high-grit Choseras and the Snow White, which really are the main impetus for this pursuit, I reckon that I would prefer those be attached to bases to prevent breakage as much as possible anyway. In which case not being able to use the other sides due to sealing is moot.

Regardless, I'm not too bullish about defending this as practical... Hopefully I'll learn something and my hones won't be any worse for the wear. Anything beyond I'll just call gravy and be happy.

I have sealed my Chosera 10k , Gok 20k, and all my jnats and Nagura stones.
Mould never occurred to me though.

The Gok and the Naguras I sealed to keep them clean and maintain stamps.
I didn't want swarf muckin up my white stones.
The 10k cracked up pre sealing , I have a feeling that had I have sealed it from new it would never have cracked up.
There is no need to seal synthetics really I just like to be extra :)

Quote:

---

Originally Posted by JOB15

I have sealed my Chosera 10k , Gok 20k, and all my jnats and Nagura stones.
Mould never occurred to me though.

The Gok and the Naguras I sealed to keep them clean and maintain stamps.
I didn't want swarf muckin up my white stones.
The 10k cracked up pre sealing , I have a feeling that had I have sealed it from new it would never have cracked up.
There is no need to seal synthetics really I just like to be extra :)

---

Whoa. Those are some nice synths there, good buddy. And even nicer nats, I'm sure.
How long have the light-colored, fine synths been sealed? If the issue of mold hadn't occured to you before, I would assume it hasn't been a problem. That's no guarantee for the future, sure, but still...
I am confused; if the 10k cracked pre-seal, and you believe that it would not have cracked if you had sealed it from new -- Why feel that sealing is unneeded? Or was the cracking not a functional problem, as others have described; but rather only a minor cosmetic issue which didn't NEED fixing in you estimation?

Finally, what did you use to seal all these up? Was it the vaunted Japanese lacquer I've heard about?
In any case, how did you like whatever sealant it was you used?
And have you subjected it to prolonged (days, weeks) exposure to water, or is only briefly exposed to water when the stones are used and until they dry?

Personally I think that sealing any stone natural or synthetic is fine but I wouldn't bother sealing lower grits,I can't see the point in that.
Maybe if I would have sealed the 10k straight away then it would have been less exposed to water and not cracked, just a guess though.
The 5k cracked but I wouldn't seal that.
They function fine with the cracks either way.

I think in the past I used to soak the 5k but I cannot recall of I soaked the 10k.
I use plastic spray in a can, quick n easy, 2 coats.
Expensive jnats I use urushi.

I've been following along and have to say that I just don't get the 'mold' issue. The sealed sides/back aren't going to mold, they're coated in something, and the face is not any different than it ever was. Overall, there will be less water in a sealed stone than an unsealed one. The only time I've seen mold is putting a damp stone away in a cardboard box and then putting it in a drawer, and I got a bit of mold on the box, not the stone (Naniwa Superstone).

As far as cracking goes, I sealed a Naniwa Snow White and it still cracked. Just one data point though.

Just be sure that your hones are well dried before you put them in a drawer or cabinet. A wet stone put away isn't good and the moisture isn't good for other things that may be in the drawer with the wet stone.

Cheers, Steve

I personally wouldn't seal them myself, I have one stone that shows some crazing a Chosera 5K I've owned it for a number of years, it's still a smooth stone that causes me no problems, I never soak my stones just spray and go, I also like them to dry naturally with their pores open in a closed wooden box at room temperature, I'm also of the opinion the SG 20K and the Snow White 8K barely absorb any water so those stones always seem almost dry to me after use.

Molds need oxygen and if it is sealed it won't mold. At least on the inside of the seal........

you know this hasn't shown that sealing helps or is bad, so far. so its totally a user choice, either or it wont make a difference. so if it makes you feel better seal it! those who don't will still have a flat stone as a guy who seals. there is only one way to tell, you need to purchase 2 full sets of naniwas, seal one and not he other, put them in a time capsule and open them up in 100 years,

I,m not sure of mold, but Tim it wont be sealed on all 6 sides, so yes mold can grow. Tc

That 2nd pristine, unused $300 10k, sitting in that time capsule, even after the near-consensus online that even one is overpriced for what it is -- that's when you know that moreso than you having HAD...
The HAD has you.

There are a number of ways to cause crazing & cracking on non clay based stones. Rapid drying is the biggest one.
Air con ,fans & bright sunlight come to mind. Excess soaking,hot water, soaps, detergents, washing soda can all soften them.
Nowhere on any instructions have I seen a recommendation to seal them but sealed or not, the above conditions would still damage the stone.

The only synthetic that crazed on me was a 12k Shapton Ha no Kuromaku which was left on a sunny bench & dried too fast.

Quote:

---

Originally Posted by holli4pirating

I would worry about sealing 5 sides, because water that penetrates into the bottom of the stone would have no easy way out. Then again, maybe that would cause a slower and more even drying process... It will also be interesting to see what it's like honing on top of a pool of water... It will be an interesting experiment.

---

So, a few months later and a few pounds heavier...

I finally felt the need to hone a razor on the permasoaked King Deluxe 1k I sealed in spar urethane last year -- I've used it a few times on knives and sundry things since then, but no razors until today; and I figured I might as well report back with some thoughts:

I'm finding the properties of the sealed King pretty great, actually: It doesn't dry out at all, that means no needing to add more water which sometimes spills over the sides if I add too much, whilst also diluting the slurry even if I'd rather keep it as is.

In fact, slurry is why I felt like grabbing the King today -- I wanted something which would muddy more than the Chosera 800 I was working with, even with the very light pressure I'm using on a supple full hollow grind. The King fit the bill nicely and this way the slurry doesn't dry into thick mud too quickly, or at all in fact, which is how I like it for a razor.

Not drying out on account of the stone being waterlogged and the sealant preventing water egress from the 5 sealed sides also means that for once there isn't a puddle forming under the King. Another nice win.

On the other hand, if someone is in the habit of using the stone's drying out to their advantage, perhaps because they've intergrated the progressively dryer mud into the way they use the stone, they could be frustrated by how wet the surface stays virtually indefinitely -- although I don't find working the mud on a 1k King in this fashion to be useful for razors. Regardless, the slurry's remaining completely wet and not drying to a thicker mud does hamper the stone's tendency to impart a dark hazy finish, based on the few knives and chisels I've experimented with.

Those are the more pertinent observations I can think of with regards to the actual usage of the sealed permasoaked King. That said, there are a few other little nuggets of dubious usefulness I've collected:

The thinner coats of urethane I used on the King 1k worked well compared to the Naniwa dressing stone; that and allowing for roughly double the curing time between coats resolved having parts of the sealant remain soft, absorb water and discolor when submerged for long periods.

Once submerged for a while, the surface texture of the urethane went from smooth to bumpy -- I think it must be tiny bubbles trapped by brushing, which expand with water. I left the stone to dry out once -- it does take much longer to dry out completely now -- and the surface regained it's smoothness. So -- and not that it matters -- but if I did seal Choseras in a similar fashion I do not think their coating would feel rough like the soaked King's, on account of much shorter exposure to water.

All told, the sealant has been underwater since shortly after my last post here, and it's held up fine. I am however careful not to let the coated surfaces rub or knock against other stones because I doubt that it would take much to lose the watertightness.

Also, the sealant layer has a tendency to stick around even as the stone is worn down beneath it from usage. Hence I have to take care to cut/grind the extra sealant at the edge where the top meets the sides as part of maintaining/flattening the stone, otherwise pieces of sealant flake off. Because of this, I've slightly tweaked my usual way of chamfering the edges with a diamond plate to be more deliberate way than usual: making an effort to cut the layer without pealing it from the stone.

I must say that a more strongly bonded layer, epoxy for instance, presumably wouldn't have either of these last two issues. Cost notwithstanding...

Finally, looking back on this thread I remembered that mould had been brought up as a concern -- although I believe that it must have been in reference to my plan of eventually sealing Choseras rather than the the intermediary step of the permasoaked King stone; because Choseras must be dried between uses, almost by definition; at which time mould could become an issue, I'm assuming -- In any case, Sealing the King hasn't changed anything with regards to mould: a cap full of bleach every few weeks, when I change the water in its happy little bucket aquarium, has worked very nicely so far.

One of these days, I'll finally get around to sealing my Snow White like I've been meaning to.