Jnat Care?

Miura knives
Shop Knives and stones on ebay
Kitchen Knife Forums

Help Support Kitchen Knife Forums:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
mikedtran

mikedtran

Banned
Joined
Aug 26, 2015
Messages
1,395
Reaction score
21
Starting to get more into Jnats and wanted to ask a bit more about care. I've read Maksim's faq and some general things:

-Don't contaminate with synthetic stone powder
-Lacquer stones
-Attached thin stones to bases

Questions:

-Should I remove mud off a stone after sharpening? Can the residual metal rust?
-How bad is getting oil on a natural stone or a synthetic stone even?

Would love any other advise for taking care of natural stones =)
 
Dont know about the oil, but def lacquer it. You can wipe the fresh wet mud from the stone with a paper towel and rub it on a finish after fingerstones to further polish it.
 
A comment on the synthetic powder advice.
I think what he means is that you should clean it well. If there's any small cracks or holes in your stone a bit of slurry from the lapping proces could get embedded in them. And that would ruin your day if you during the finishing stages accidentally scratched up a finish you spent hours polishing.
 
And about the oil. Oil is fine on some stones not on others. I only use oil on non porous stones. It would be super annoying to get it on a stone that soaks up water. Synthetic or natural. I once accidentally spilled oil on a thuringian. It has bothered me ever since. But then again it's totally fine on Arkansas stones and the like.

I probably never would use oil on a jNat.
 
Mika said:
And about the oil. Oil is fine on some stones not on others. I only use oil on non porous stones. It would be super annoying to get it on a stone that soaks up water. Synthetic or natural. I once accidentally spilled oil on a thuringian. It has bothered me ever since. But then again it's totally fine on Arkansas stones and the like.

I probably never would use oil on a jNat.
Click to expand...

Not so much using oil on, but was curious if I accidentally got oil on one. I have accidentally gotten a bit of oil on some synthetics and I feel it is more aesthetic than any real effect on the sharpening. Was wondering how "horrible" it was if I got some on a natural. I will just have to be more careful =)
 
For what it's worth I've had bits of oil on a couple of more stones in the past, and it hasn't mattered really at all aside from initially being an annoyance, and then after a bit of diamond rubbing or time the oil spot would disappear. I'd guess that, unless you're a really subtle skilled razor sharpener, I don't think any knife sharpener would notice changes to the slurry if you had a small oil mishap.

Density/structure - I think you can use your common sense and figure things out when you have a new stone most of the time. Kyoto finisher-type stones are going to be layered and that is their general structure, unless in you're in suita territory with the crazy lines. Aoto are layered perpendicularly. Not many other layered stones out there. Of the many potential rest, you've got to think about how they feel (you can tap them, feel them, notice their sound and response when sharpening..) and you can get a feel for their density and how 'together' they are maybe also on a finer level, and if they'll react pretty uniformly to water or not. If not, then the stone might be less stable and bits can break off or a fissure can appear. Sure lacquering is good, but lacquer will also penetrate in and force open small cracks and generally challenge the more exterior area of the stone when applied, I think. When you get past that and the stone's survived then you'll be better off. Some stones seem to get lots of surface cracks too, but they don't seem to penetrate in a threatening way they seem just be part of the personality of that stone

About leaving slurry on stones, I think this is done a lot. Saves you from generating new slurry next time, looks a bit messy yes, but can be more convenient and lessens wear and tear. Thinking of rust, one of us can speak with a Chemistry grad or a geologist or someone, perhaps, that could tell us more about the PH, etc, that we might be working with and how the type of water you use, the steel and stone all react together, and that could be useful. I've noticed how if you have a reactive knife and get a bit of water on it you'll get the rust, but then if you are busy sharpening that knife for a while and it's in contact with plenty of water + slurry (not sure about synths so much) it seems that reactivity is low or pretty unseen. Hmm, thinking of it some nats seem to discolour a bit from use, so there's a bit of brownness due to rust/oxidisation, but not usually. They'll all have different properties but it's hard to guess and know unless you try things out and get to know the stone and how it does with what you use it with.
 
Nice answer Asteger. Very informative post.

The problem with getting oil on some stones isn't that it affects the slurry fases. but it is that water tends to bead on the stone if oil has been used. So it affects the feedback and how the stone behaves during water only sharpening.
 
Last edited:
This is really helpful! I had no idea that lacquering could actually create cracks.

Curious on if people find lacquering suitas especially softer ones to be valuable or if it is unnecessary? (I'm guessing there is a range, but wondering generally)

I have yet to see rust appear on any of my left over slurry. I'm sure it could be diamond plated out if it did. I have also seen the same thing when I'm doing polishing where I'll sometimes see a bit of discoloration on the blade if I've been at it for a while.

Asteger said:
For what it's worth I've had bits of oil on a couple of more stones in the past, and it hasn't mattered really at all aside from initially being an annoyance, and then after a bit of diamond rubbing or time the oil spot would disappear. I'd guess that, unless you're a really subtle skilled razor sharpener, I don't think any knife sharpener would notice changes to the slurry if you had a small oil mishap.

Density/structure - I think you can use your common sense and figure things out when you have a new stone most of the time. Kyoto finisher-type stones are going to be layered and that is their general structure, unless in you're in suita territory with the crazy lines. Aoto are layered perpendicularly. Not many other layered stones out there. Of the many potential rest, you've got to think about how they feel (you can tap them, feel them, notice their sound and response when sharpening..) and you can get a feel for their density and how 'together' they are maybe also on a finer level, and if they'll react pretty uniformly to water or not. If not, then the stone might be less stable and bits can break off or a fissure can appear. Sure lacquering is good, but lacquer will also penetrate in and force open small cracks and generally challenge the more exterior area of the stone when applied, I think. When you get past that and the stone's survived then you'll be better off. Some stones seem to get lots of surface cracks too, but they don't seem to penetrate in a threatening way they seem just be part of the personality of that stone

About leaving slurry on stones, I think this is done a lot. Saves you from generating new slurry next time, looks a bit messy yes, but can be more convenient and lessens wear and tear. Thinking of rust, one of us can speak with a Chemistry grad or a geologist or someone, perhaps, that could tell us more about the PH, etc, that we might be working with and how the type of water you use, the steel and stone all react together, and that could be useful. I've noticed how if you have a reactive knife and get a bit of water on it you'll get the rust, but then if you are busy sharpening that knife for a while and it's in contact with plenty of water + slurry (not sure about synths so much) it seems that reactivity is low or pretty unseen. Hmm, thinking of it some nats seem to discolour a bit from use, so there's a bit of brownness due to rust/oxidisation, but not usually. They'll all have different properties but it's hard to guess and know unless you try things out and get to know the stone and how it does with what you use it with.
Click to expand...
 
Thanks, chums

Mika said:
The problem with getting oil on some stones isn't that it affects the slurry fases. but it is that water tends to bead on the stone if oil has been used. So it affects the feedback and how the stone behaves during water only sharpening.
Click to expand...

That's a good point, though I'm still not sure how much it'd actually effect the feedback. I'm guessing the stone would feel the same with the blade on it, but I'm not about to experiment to check.

mikedtran said:
I had no idea that lacquering could actually create cracks. Curious on if people find lacquering suitas especially softer ones to be valuable or if it is unnecessary? (I'm guessing there is a range, but wondering generally)
Click to expand...

Well, I guess the point is that the potential cracks are there anyway and, if you see them more following lacquer and if the stone hasn't disintegrated when lacquering, then you've passed the critical period. Surely you'd be in trouble if the sides weren't sealed on a stone like that and you proceeded to use it unlacquered. Some unlacquered stones are fraqile if not used previously - maybe kept in storage for decades, then shipped here and there via delivery trucks, via international cargo holds, with changes in humidity and air pressure, etc - and so if you get them like this the first time you use them, applying water or lacquer, they're at their most vulnerable. I guess it's an argument then for buying stones that have already been lacquered and tested, if not already used a lot, as they'll be broken in and should be stable. Therefore JNS stones will be safe, even if the lacquering Max or his secret partner who actually selects the stones in Japan, is usually kind of slipshod and can be disappointing on the more expensive stones much like a plastic ferruled handle would be on a pricey honyaki.

Hmm, I hadn't heard about this before so in the past haven't paid as much attention to things when lacquering, but sure the lacquer penetrates and cracks will show, much like with water. Not sure if they show more visually with lacquer compared to water, or if not, and it's more a visual thing. Not sure if it depends on the type of lacquer either. However, the point of the lacquer is you do want it to penetrate and fill in the cracks, so then repeated water infiltration and expansion/contraction, especially most often on the sides, doesn't become an issue and the thing is pretty stable. I wouldn't worry about the lacquer actually damaging the stone because if the lacquer does that then surely water would have too, and so then that's just the nature of the stone you're stuck with.
 
Thanks for clarifying! I had read your post a bit quickly and this part "but lacquer will also penetrate in and force open small cracks and generally challenge the more exterior area of the stone when applied, I think." is the part that got me scared about lacquering sounds like it is worth lacquering all stones.

I actually just ordered a stone from Japan and will ask them to lacquer before sending. =)
 
mikedtran said:
Thanks for clarifying! I had read your post a bit quickly and this part "but lacquer will also penetrate in and force open small cracks and generally challenge the more exterior area of the stone when applied, I think." is the part that got me scared about lacquering sounds like it is worth lacquering all stones.

I actually just ordered a stone from Japan and will ask them to lacquer before sending. =)
Click to expand...

I guess 'force' was a strong word, but who knows because different liquids can work differently in different ways, and maybe fissures can appear where things might have been fine before.

Lacquering before - I'd still like to do it myself, though less convenient. Maybe not the best for most people, but okay for me. Usually you can shape the stone first then lacquer, for eg. Many times in the past I've thought the lacquer was a mess, then taken it off myself in order to re-lacquer. As kind of said before, you get nice stones with some pretty messy lacquering on them, which seems a bit amiss.

Almost everyone will use some sort of shellac, which is usually good, or maybe artificial lacquer which I don't know about, but would be suspicious of. Maybe I've had some before but not know. You can also do cashew which should be the best, well maybe with urushi, but that's only if you're interested. Best to do it yourself, then, if interested.
 
What does lacquer mean and how do you do it? (I'm not a native english speaker.)
 
Im happy with the results, but I wish I wouldve chosen a different color than black lol. May try blue though...
 
YG420 said:
Im happy with the results, but I wish I wouldve chosen a different color than black lol. May try blue though...
Click to expand...

Black for Tsushima, of course, and I think it looks good on aoto too, which usually aren't great lookers as far as stones go to begin with.
 
Lacquer is a term for an organic material dissolved in an organic solvent that forms a thick, solid, shiny film when the solvent evaporates. Traditional lacquers are of natural origin, either plant or insect extracts. Shellac is the one most commonly available, being dissolved in dry ethanol. They are resistant to water, some more than others as shellac softens some when wet.

Japanese lacquers are mostly cashew extracts (of what part of the plant I do not know), and hence are highly irritating if gotten on the skin while dissolved, shellac is quite non-toxic.

Synthetic lacquers are nitrocellulose or some other synthetic material dissolved in an appropriate solvent.

The difference between lacquer of various types and other similar finishes like varnish is that they easily re-dissolve in the appropriate solvent, they do not chemically change as the solvent evaporates. Paints and varnishes DO chemically change, and are no longer soluble in the carrier solvent used once dry and "set".

Hope that helps.

Lacquering natural stones limits water penetration and should stabilize cracks as a result -- most natural stones do not work better when immersed, although there are exceptions. The stone swells when soaked, as a rule, and the internal stresses produced by the changes in hydration state can split some stones, so preventing water penetration except on the working surface prevents them splitting so much.

Thin stones and stones with rough "back" sides should be mounted to make them easier to use and to support thin stones so you don't crack them in use. If the stone has a flat enough back, you can use them unmounted, but if you lacquer the back side they can slip around if not mounted.

Peter
 
Is it possible / advisable to varnish Jants ?
 
Thanks, Peter

Just a couple of points. First, I think most people know, but urushi was the most traditional J lacquer - from a certain tree found in E.Asia, from sap I think, but please google to check. Cashew of course isn't so traditional as cashews are from nowhere near E.Asia. I haven't worked with urushi, which is the one that can be toxic when not dried, but cashew I think is fine. Actually, I've not heard of it being described as toxic, so either I've missed something and also am impervious to the poison, or maybe there's some confusion with urushi here.

psfred said:
Thin stones and stones with rough "back" sides should be mounted to make them easier to use and to support thin stones so you don't crack them in use. If the stone has a flat enough back, you can use them unmounted, but if you lacquer the back side they can slip around if not mounted.
Click to expand...

It's pretty easy and save to flatten and stablise the bottoms of stones. I've done this a lot as I hate mounting and wobbly stones. Simple Atoma-action
 
... Some time later...

Just googled and found a helpful post re. the difference: 'Hon Urushi is the traditional lacquer method that is made using sap from the Kiurushi tree. It is highly toxic (urushiol is what makes poison ivy poison) and so quite dangerous to work with, but it produces a very tough lacquer coat. Cashew lacquer is made from the shells of the Cashew tree, and is also toxic (same chemical), although it is much less toxic than Hon Urushi.' http://www.swordforum.com/forums/showthread.php?111159-Differences-between-Cashew-and-Urushi-Saya-Lacquer

As said, I've dealt with cashew a lot and no reactions to it
 
You must log in or register to reply here.

Latest posts

Back
Top