Crunchy Koma

[ffourteen]

I recently bought a koma to add to my progression, but I’m finding no matter how gently I rub it to make slurry, I’m getting small particles breaking off (haven’t had this problem with any other slurry stones). The slurry feels/sounds gritty until it breaks down, and I can hear the blade hitting individual larger particles. Also, bizarrely, some of the bigger particles got trapped under the tape on a blade and left tarnish marks that I now can’t get off. Anyone experience any of this before?

 

[kcb5150]

Who sold you the nagura? Have you tried redressing the surface?

 

[ffourteen]

Got it from Maksim. One of the edges was sharp and I took that off with sandpaper, but otherwise haven’t done anything; what do you use to redress it?

 

[buca3152]

You could use a diamond plate to round off a corner. You used sandpaper on the koma? It's possible you got some of the grit in the mix. Can't say for sure from here.

 

[ffourteen]

It was crunchy before the sandpaper, and I use a good 3M w/d that hasn’t left grit in any of my other stones.

 

[buca3152]

What I would do is attempt to generate slurry several times. Try a different location on the nagura as well. If you can't get a decent slurry without too much grit then I would see about a replacement.

 

[ffourteen]

That seems to have been the solution, thanks. I also put a few drips of water on the nagura and let it sit a few minutes first. Had one particle come off and scratch my base stone, annoyingly, but beyond that the slurry now seems smooth and particle free.

What I would do is attempt to generate slurry several times. Try a different location on the nagura as well. If you can't get a decent slurry without too much grit then I would see about a replacement.