Thread: Sealing synthetic waterstones

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...

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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:


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.

This side (#2) has some drips which have turned white after the soak, it also has the same white line.


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.


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.

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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.

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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...