Jiro usage questions

[Juneau]

Hi I just received my first (and maybe last) Jiro I will ever get based upon the rarity. But I’m a professional cook, highly trained, lover and care taker of all things knives, spoons, tools you name it.

With my Jiro being BNIB (240mm WA) I noticed that the acidic ingredients (as basic as red onions) stripped the subtle Kurouchi of the knife I own in which Jiro produced. The patina is amazing however. But just the red onion juices on my fingers has left a “skid mark” on the knife of me sliding my finger down the blade to remove the produce and even where I had changed my pinch grip. It also turned my fingers colors as well as some of my onions lol. Is this super common amongst Jiro’s knives?

Yeah yeah KU comes off but I’ve never seen it come off this fast (just saying)

Again to specify I am a working chef/cook whatever; with a lot of experience but I’ve never seen red onions strip a KU so quickly. (Can post pictures). Love the formation and personalization but damn I’m a sucker for prolonging aesthetics but this one is now to be considered ‘personal’

May the knife gods shun me

Also I can attest to Jiro’s having crazy performance. #324

 

[Corradobrit1]

Yeah yeah KU comes off but I’ve never seen it come off this fast (just saying)

Not on a TF. If there have been any changes over the years on my Denka's its been super subtle.

 

[M1k3]

Not non a TF. If there have been any changes over the years on my Denka's its been super subtle.

TF? He's talking about Jiro...

 

[Bico Doce]

That fake ku isn’t meant to last. It’s completely normal to lose it relatively quickly. I wouldn’t worry about it. Once it’s all gone it should look better. Think of that in between phase as puberty

 

[Mikeadunne]

@Runner_up had an impressive looking restore on a jiro. You can reach out to him on insta (at a cut above brookline), had a couple interactions w him he’s a good dude.

Edit, to be clear. Restored the ku specifically.

 

[Heckel7302]

That fake ku isn’t meant to last. It’s completely normal to lose it relatively quickly. I wouldn’t worry about it. Once it’s all gone it should look better. Think of that in between phase as puberty

Jiro KU seems looks natural to me. I highly doubt he paints anything on.

@Juneau I haven’t noticed this in my home use (240 wa #388). Maybe you had some super acidic onions? It would be interesting to see pics of what you are talking about.

 

[Bico Doce]

Jiro KU seems looks natural to me. I highly doubt he paints anything on.

Maybe but I’ve never had a legit ku fade at the rate of a Jiro or other knives I suspected to have a fake ku.

Also that crisp shinogi line on the ku doesn’t actually coincide with a bevel on my knife. There’s no way that ku was left like that after he shaped and polished the knife with stones. This is not a criticism of his methods just observation

 

[Heckel7302]

Maybe but I’ve never had a legit ku fade at the rate of a Jiro or other knives I suspected to have a fake ku.

Also that crisp shinogi line on the ku doesn’t actually coincide with a bevel on my knife. There’s no way that ku was left like that after he shaped and polished the knife with stones. This is not a criticism of his methods just observation

I certainly don’t have any evidence to back up the claim, just seems antithetical to his whole philosophy to put on an artificial finish.

 

[Juneau]

Jiro KU seems looks natural to me. I highly doubt he paints anything on.

@Juneau I haven’t noticed this in my home use (240 wa #388). Maybe you had some super acidic onions? It would be interesting to see pics of what you are talking about.

 

[enrico]

Looks fine.

 

[Juneau]

Want to note that this knife was babied though cutting through several pounds of vegetables such as: zucchini, yellow squash, red bell pepper, green bell peppers, red onions, and a few lemons and limes. Always kept dry using 2 MICRO FIBRE towels at some of the highest rated weave I own, one for wiping and and one drying. Oiled after service using tsubaki oil dabbed on eye glass cleaning cloth

 

[Juneau]

Looks fine.

Knife wise, it’s great. Aesthetically it looks like I’ve had it for years and with it being a potential (specific) daily driver, and for only a few days it looks like a new tattoo that has seen some ocean time and showers and rapidly began to fade.

All in all I love the knife I just want to make sure I’m taking care of it as I’ve done with all my others. This one is just a a little different. And the KU on this one just seems exceptionally and I mean exceptionally….temporary.

Also to note, most of my knives are stainless cladded (some with and w/o KU) so this being a fully reactive knife @ YW#1 I new it would need extra attention. So I gave it all my love I could but the acid still got the better or worse of me as per usual (joke inserted lol)

 

[Delat]

Sounds like the cladding is super-reactive if it’s turning onions brown. If that’s the case, you might want to force a patina by soaking the blade in some extra-strong instant coffee for a few hours (I usually do 24 hours with a wash and wipe midway but about 6 hours gets you most of the way there). Or maybe cut some cooked proteins. It should settle down once you have a solid patina though.

I personally don’t have any knives where the ku was removed by onions - that does seem like unusually fragile ku to me.

 

[Juneau]

Sounds like the cladding is super-reactive if it’s turning onions brown. If that’s the case, you might want to force a patina by soaking the blade in some extra-strong instant coffee for a few hours (I usually do 24 hours with a wash and wipe midway but about 6 hours gets you most of the way there). Or maybe cut some cooked proteins. It should settle down once you have a solid patina though.

I personally don’t have any knives where the ku was removed by onions - that does seem like unusually fragile ku to me.

In fact it didn’t turn them brown. Again this is all new to me using YW#1 (mainly. Aiogamj user) but the onions took a blue’ish hue. It was oxidation, but more of what I believed the KU rapidly stripping and adhering. Even my fingers were stained black/green’ish.

I’m probably going to avoid acidic ingredients and most rock chopping mise’ with this knife going forward to preserve it

 

[Juneau]

I personally don’t like the idea of forcing a patina and not a huge fan of the concept. Coffee mustard w.e. And most especially with a Jiro. But I’m not against it or personal preferences.

In fact it didn’t turn them brown (the red onions). Again this is all new to me using YW#1 (mainly. Aiogamj user) but the onions took a blue’ish hue. It wasnt oxidation, but more of what I believed the KU rapidly stripping and adhering. Even my fingers were stained black/green’ish.

I’m probably going to avoid acidic ingredients with this knife going forward to preserve it. The patina is amazing and already coated the blade. I’m just looking for opinions from users and everyone in which I’m most appreciative.

 

[Corradobrit1]

TF? He's talking about Jiro...

He said "Ku comes off", which I read as a general statement. Not the case for all makers.

 

[inferno]

there are several ways to get a blade black.

quenching in oil - quite thick and durable.
forging/ht-ing for a prolonged time - quite durable

"hot/cold bluing solutions" - skin deep

accelerated rust bluing - quite thick and durable. (this process involves rusting the blade in acid and accelerating it with hydrogen peroxide and then boiling it to make the red rust black.

and then my own fave. dunk in oxalic axid. it will even blacken stainless. neutralize with a base.
redo until satisfied. you can also do boils in between to stabilize the rust formed. this is slightly thicker than skin deep but less than oil/forge/rust bluing. but its easy and quick. and cheap.

 

[JFolmer]

Don’t worry about it, the kurouchi often rubbs off with a wet towel on a Jiro.

Both my Jiros have lost almost all of the kurouchi. Only to a collector will it inflict on the price.

 

[mozg31337]

A very interesting feature of Jiro KU finish. I don't own a Jiro (yet) and I have plans to buy either a Nakiri/Santoku or a Gyuto sometime this year if I could find one for sale. I wouldn't have thought that KU finish is that unstable in Jiro knives. I have KU finish from Shig, Watanabe and Toyama and have been using them for many years. the KU actually stays pretty much untouched. I've compared some of the old pictures that I took when I just got the knives and the KU is there and looks pretty much the same apart from maybe a mm shorter due to sharpening / polishing.
I wonder if there is a KU retention treatment that will make KU stay on Jiro knives? Any thoughts?

 

[Corradobrit1]

A very interesting feature of Jiro KU finish. I don't own a Jiro (yet) and I have plans to buy either a Nakiri/Santoku or a Gyuto sometime this year if I could find one for sale. I wouldn't have thought that KU finish is that unstable in Jiro knives. I have KU finish from Shig, Watanabe and Toyama and have been using them for many years. the KU actually stays pretty much untouched. I've compared some of the old pictures that I took when I just got the knives and the KU is there and looks pretty much the same apart from maybe a mm shorter due to sharpening / polishing.
I wonder if there is a KU retention treatment that will make KU stay on Jiro knives? Any thoughts?

I believe the makers use a pickling solution to stabilise the finish, at least for the SS clad Denka's. You could maybe ask Gaku @Isamitsu what they use. If there has been any change on my Denka's Ku finish after daily use, over the past 5 years, it's barely noticeable.

 

[Heckel7302]

I believe the makers use a pickling solution to stabilise the finish, at least for the SS clad Denka's. You could maybe ask Gaku @Isamitsu what they use. If there has been any change on my Denka's Ku finish after daily use, over the past 5 years, it's barely noticeable.

Only change in my Denka's ku is from where I slipped when thinning it.

 

[Namaxy]

That fake ku isn’t meant to last. It’s completely normal to lose it relatively quickly. I wouldn’t worry about it. Once it’s all gone it should look better. Think of that in between phase as puberty

This has been my experience. Standard folded towel wipe after cutting had brown streaks on the knife, brown on the towel etc. But it ends. No effect on performance. I go hot and cold and back again on patina....Usually like it but I tend to get all aestheticy (if that's not a word it needs to be) when I sharpen. The business end cleans up just fine if you want that. I'll say I certainly have knives that are more reactive.

 

[Hassanbensober]

I’ve grown into my jiro I must say. But it was and for me still is incredibly disappointing to buy a very expensive kurouchi knife and literally in the first 20 minutes the whole aesthetic finish I loved about it was coming off before my eyes.
Still a bad ass knife but I wish I never touched it. Should’ve done my homework on them

 

[SWF]

Using a microfibre towel to clean a ku-knife isn't really a good idea. You could also use sandpaper with a similar result.

But it looks like those Jiros have a quite instable ku-finish. Really bad when it's gone, because the ku-finish is what these knives make them nice.

 

[Corradobrit1]

Using a microfibre towel to clean a ku-knife isn't really a good idea. You could also use sandpaper with a similar result.

But it looks like those Jiros have a quite instable ku-finish. Really bad when it's gone, because the ku-finish is what these knives make them nice.

Obviously depends on the Ku. Microfiber has zero effect on my Ku knives from TF, Kiyoshi Kato and Morihei. A scourer is risky so thats where I draw the line.

 

[SWF]

Obviously depends on the Ku. Microfiber has zero effect on my Ku knives from TF, Kiyoshi Kato and Morihei. A scourer is risky so thats where I draw the line.

Ok, good to know. Then the ku of the Jiro isn't really stable. This is really strange and not really a quality bonus on such expensive knives.

 

[Corradobrit1]

To me the Jiro Ku doesn't look like any forged finish I have seen on another brand. To me it seems like there has been some post furnace enhancement and the fact it's not stable suggests that too.

 

[Genghis_F]

TF? He's talking about Jiro...

All roads lead to TF…

 

[superworrier]

It kind of looks brushed on

 

[Corradobrit1]

It kind of looks brushed on

Certainly does. Take a look at this closeup and see how the application is 'brushed' or mopped along the blade with a few additional strokes over the kanji. Take a look at any other Ku finish from the likes of Kato and Morihei who also chisel the kanji and there is inevitably some disturbance in the underlying metal or exposure. Not so with the Jiro which is perfectly even. That is not a natural Ku effect.