Broken rock, or not? A Jnat dilemma.

[Dave Sl8r]

First things first. Hello.
I gave a introduction to myself earlier today in the newbie check-in section of the forum. With a little more detail into the acquisition of this stone. If anyone is interested in reading it. I basically said it’s you folks fault. (JK)
My level of experience, and my knowledge base is zip, nada zero, when it comes to Jnats, except for the little information I’ve picked up from this site, and searching the internet recently.
I do however have a good bit of experience with and reasonably full sets of DMT, Chosera, Shapton, and a few Arks from over the years.
Now a couple of questions please.
After a few weeks of looking I finally found, ordered, and received this Jnat and nagura. I was all excited and about to seal these two with West systems GFlex marine epoxy.
#1
Can anyone think of a good reason NOT to use GFlex https://www.westsystem.com/specialty-epoxies/gflex-650-toughened-epoxy/ to seal the stones. The link is for product information purposes only.
I’ve use it exclusively when I’m looking for good penetration, adhesion, and flexibility for boat hull repairs. I also already have it in stock.

Even though I haven’t used the stone much yet. I wanted to get it sealed first while it was dry.
It is exactly what I was looking for to this point. Maybe I’m being a little too optimistic, but I try hard not to be a negative Nancy.
Unfortunately under closer examination I found the stone has a very small fracture across the top. When I run a razor across it, I don’t feel it, however I just have no idea what I should expect here, or if the fracture is of any consequence now or in the future.

#2 Should I seal it up, use it, and enjoy it ,throwing caution into the wind, or send it back?

Your opinions and feedback will be greatly appreciated!
Dave

 

[kcb5150]

Aah, the squiggly lines on jnats. I had that issue badly with one jnat but I knew what I was getting into going in and ot was a super thick brick. I think it has to do with seams/grain in the stone. Sometimes you can lap, leave them and they behave, other times the very top overlapping edge chips out and leaves big particulate in your slurry so it is best to try lapping it out.

 

[stone and strop]

I would have to agree.
The flexible epoxy should be fine as well.

 

[alex1921]

Give it a good lapping and see how the line moves. I have a couple of very hard rocks that it doesnt really move, probably just goes down towards the back. That's good. No issues there.
On a softer one the line started moving and eventually a chunk came off leaving a crater.

 

[Dave Sl8r]

Thank you for your replies.
I have no idea what the stamps mean. Can anyone interpret them? Are they significant? It’s obvious if I use, and lap this stone they will be wiped out.
Just to make sure we’re all looking at the same concern.

 

[Gamma]

Lap it - if the end of the line that does NOT terminate a the edge begins to move toward the end of the line that DOES terminate at the the other edge, you will probably be able to chase the squiggle out of the stone. It seems that the end where it runs over the side goes about 1/2 way into the chamfer, so it is entirely possible that is how far you will need to lap.
BUT - if the center portion of the line goes deeper (dice roll please) then all bets are off - anything can happen.
If you don't feel it now, good. But you can almost bet that with use you will eventually feel it. That line will allow water in and the edge of the fissure will be thin enough to take on water and it will degrade and crumble. Sometimes though, miraculously, the line just sits there unscathed. But that is an exception, a severe exception.
When I seal stones, I get the best penetration and protection using first very thin, and then progressively thicker, coats of lacquer in a traditional manner, it's dimensionally stable and easily repairable. Nail polish works amazingly well actually, nail polish is a good thinner. The ideas is to get the lacquer into the stone, very thin coats will do that. Then build up.

 

[kcb5150]

This is the one I am talking about. Mine was a bad case so I got it for a song. The main squiggle went almost to the edge and then u turned to the middle before disappearing. I am not naive though, I know full well more may crop up in the future but it's thick and the good zone I hit has been very very good.

 

[kcb5150]

My best guess is that will move along with that fine line in the chamfer. Hopefully it is as shallow across the whole rock and nothing releases during all this leaving pits. It could be painless or time consuming to get under control.

 

[eKretz]

I have had a couple with those. On the ones that were troublesome I dribbled just a touch of CA in the seam and clamped over it with some parchment paper until it was cured all the way. After lapping never had another issue and couldn't feel it while honing. These were fairly hard stones, not sure if it would be troublesome on a softer one.

 

[Steve56]

You can brush any crack with a fiberglass brush to remove unstable material, so it doesn’t release rubble while slurrying/honing. That’s what I usually do. If the ‘bias crack’ - Alex Gilmore‘s term for a crack that’s nearly parallel to the surface - is very shallow, there may be a large area of unstable material and lapping through it usually works because it’s shallow. If there are a lot of them through the entire stone, you’re screwed.

 

[SliceOfLife]

I had a mystery stone (I suspect was a Schwedenstein), that had that problem... It started out almost 2" thick... was about 1/2" by the time I FINALLY lapped past those "bias cracks". By far the worst I've ever seen. usually it can be done... but there are cases where it basically ruins the stone.

 

[David]

These cracks have started to show up in my Markua. It’s thin as it is so I hate to start lapping to try and get past them but it may be my only choice.

 

[Steve56]

Got an image David?

The first thing to try is the fiberglas brush which simply removes unstable material. That and a couple of thick Mikawa slurries should stabilize it until the next time that you lap it. Repeat after lapping.

For holes and vugs (su), I have seen jnats in Japanese auctions that clearly have automotive lacquer putty in them, and a lacquer product is consistent with historical practices with jnat cracks, etc. I saw a stone or three with green spots on the surface. At first I thought it was a camera/flash artifact, but then I realized that they’d filled the defects with automotive body lacquer putty, which is typically bright green.

I’ve also seen Bondo (automotive dent filler) used on highy serrated corners to stabilize valuable stones.

So if all else fails, you might try lacquer putty. You should be able to remove it with an alcohol soak if you don’t care for the results, but I have not tried this.

 

[rideon66]

I had one like that. Just ended up needing a bit of lapping and problems never resurfaced. Had an iromono with pits that just never stopped had to turn it into tomo nagura. So could go either way.

 

[David]

Got an image David?

Here ya go. When I’ve tried to lap past them they just reappear in different places.

 

[rideon66]

Mine was about the same as the op. It is gone now but took a bit of lapping luckily is stuck to that one area too.
You can see it in the main image before I ever lapped it on the right side about 2 inches up.

 

[Steve56]

Here ya go. When I’ve tried to lap past them they just reappear in different places. View attachment 1052368

Those that come back in other areas are pesky. They’re light enough, so the first try would be a fiberglass brushing followed by raising a thick sticky slurry using a good bit of pressure. Rinse well and hope that they don’t shed.

I have a small chocolate iro that’s covered with those bias cracks. They’re tiny but everywhere. Their edges turned loose when I lapped it with SiC which is very hard on the surface, but afterwards they’ve been stable.

 

[iamryan25]

On arrival from previous owner before I started working on lapping, I noticed the squiggles right away and thought to myself boy I sure hope I can get under those.

After some labor on the worn out DMT 325 which is not as aggressive as it was 3 years ago, I made some progress but revealed more than I expected to see.

I guess some are disappearing on the left side lower area but I'm still pretty squiggly on the right side of the stone.

A closer look at what I'm dealing with:

View attachment DSC00005.JPG

They seem "less" noticeable now after lapping than they were before. The lines dry faster than the surrounding material, I'm guessing they're taking up water differently than the surrounding material.

That is a lot of squiggly lines, too many? What would you do?

 

[alex1921]

The way they look lighter at the edge it looks to me they are ready to flake, not good. I would keep lapping.

 

[MasterOfPups]

If you are comcerned and it is a new stone, you might want to return it . Yeah, you can probably stabilize it with thin super glue, but why take the risk on a brand new stone, especially if you paid retail for it. There are tons of good stones out there if you have the patience.