Thread: 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.