New knife problem :(

Hey guys.
I'v bought couple days ago a tojiro shirogami nakiri knife...got it for cheap 35$ but thats not the case.
I came to work and started cutting with it...after 10 minutes it got rust spots and colored the vegetables i was cutting in black/purple color...
here is some pics of it:




any ideas what can cause this?

It's a carbon steel knife. If there's any moisture on it for prolonged periods of times it will rust. There's people here who are much more qualified to give you tips on how to prevent this, I'd recommend waiting for other people to give you some good advice.

so what is the solution for it? i can throw it to the garbage?

No no, It's easy to get rid of the rust. Don't throw it out!

I seem to recall a member having the same problem with the same knife. He was a pro as well, I think he moved onto another knife. I'll search and see if I can find the thread.

Dave Martell said:

I seem to recall a member having the same problem with the same knife. He was a pro as well, I think he moved onto another knife. I'll search and see if I can find the thread.

Click to expand...

http://badgerandblade.com/vb/showthread.php/313656-Japanese-White-Steel


http://www.kitchenknifeforums.com/showthread.php/11102-discoloring-of-onions-blackness

god damn carbon steel knives

It's not the carbon steel that's the problem, its the cheap iron cladding

You could scrub it with a green Scotchbrite pad to see if that will remove the surface rust. You can also us a product call Bar Keepers Friend its powder for cleaning metals to lightly scrub off the rust. Keep in mind BKF is slightly acidic and needs to washed off completely or neutralized with some baking soda. The point is use the least abrasive method to get the rust off.

The steel appears to be highly reactive so you will want to set a patina to reduce the reactivity with acidic foods. You do this by having the blade in contact with something acidic. Using mustard to do this is a popular method. Smear the blade with mustard and let it sit for 45 mins or so. Wash off the mustard and you should be good to go. There are good threads about setting patinas in the forum

Don't think it's exclusive to "cheap" . A new shig did that with onions, neither knife or onions were pretty. Wipe it down, clean it off, cut more onions. Repeat. (I kept a stainless nearby for when onions had to be pretty) . It settled down quickly.

A couple of times using Bar Keepers Friend will actually cause a very light patina to form on the blade.

First, wash the knife with some bar keepers friend. Then just use the knife normally but keep a wet towel and a dry towel handy. Every time you finish cutting something just wipe the blade on the wet towel then dry it. Once you form a patina the reactivity should settle down a bit.


Different products will cause different colors on the blade. Onions, tomatoes and other acid foods will cause yellows, browns and blacks. Proteins like fish, chicken, beef etc will cause blues, reds and purples.

That happens with new carbons before patina is formed,stains food rusts quickly.You can force a patina with white vinegar & mustard.

Wash your blade wt. warm soap & water after use & oil it if not using it for even a few days.

These Tojiros seem to be real stink monsters, not the normal carbon knives at all. Are they made from iron?

i had a tojiro gyuto in the same series. horribly reactive at first but after a bit of use, it settles down. the kurouchi finish comes off really easily and it is probably the most reactive knife i've used. handle is just about as low you can go.

however, the real ****** thing about it is the grind. it's so thick behind the edge that it just wedges through stuff. you get what you pay for i guess.

at first, it seemed to tick a lot of boxes.
kuro finish
wa handle
white#2 core

but i would not recommend ever.

A very nice patina can be forced on this knife just by doing what you started. Get several more of these onions, cut them one at a time into thin slices. wash, wipe and dry the knife between each onion but don't scrub off the color/patina that is forming. after three or four onions the coloring and rust will stop and the finish will stabilize.

thanks for your help guys... the thing is while im on abusy service at work its hard to maintaine it that why...how much time will mustard patina will hold?and im from israel i dont think we have here bar keepers friend..what alternatives i have?

Just use a green scrubby on it. I have a tojiro gyuto and it rusts super fast like this. Just keep it clean and dry when not in use and if rust forms remove it with a scrubby or an erasor.

These knives are very cheaply made but if you put time into thinning and profiling they can be a lot of fun. I rehandled mine and I really like it.

I had this knife, probably the most reactive cladding I have encountered, except for perhaps a Moritaka petty. Impossible to passivate*, which in my mind makes them junk, unsuitable for preparing food. YMMV, especially if you don't mind the taste of iron/oxides of.

*TTB, D.Phil. (Chemistry)

I simply will not use a clad carbon for onions, garlic, shallots or citrus.

The later will strip any patina you've worked so hard to build on the iron.

Iron cladding can be miserable, initially.

Dave Martell said:

.... Are they made from iron?

Click to expand...

....or are they NOT lacquered? Both of my CCK's see pretty regu;lar use, one is a daily chopper, and I can just now see the lacquer starting to wear/scrub off...?

CCK has very heavy lacquer. But it does wear off, and will be quite reactive itself.

The worst part about the itk series is that the kurouchi is crap. It will literally wash away, leaving the super reactive iron exposed. This is where heavy forcing of patina will come in handy, but can be tricky on iron.

NO ChoP! said:

CCK has very heavy lacquer. But it does wear off, and will be quite reactive itself.

The worst part about the itk series is that the kurouchi is crap. It will literally wash away, leaving the super reactive iron exposed. This is where heavy forcing of patina will come in handy, but can be tricky on iron.

Click to expand...

This.

Whatever they use for the cladding, once exposed it's impossible to passivate satisfactorily.

Honestly why I moved away from iron cladding.

I have a petty from this line. Quite reactive at first, but it settles down. This is not at all exclusive to cheap knives. Konosuke Fujiyama and Shig have had similar issues. At first, you have to either force the patina (various ways mentioned above), or carefully monitor the one that develops naturally. It will take more wiping at first. But once the patina develops, it forms a largely non-reactive layer on the surface of the metal, and will require much less care.

The KU finish did wear in spots pretty quickly, so I used a green scrubby to remove all of it. After forcing a patina, it has settled down quite a bit--acceptable for my home use.

I have a Damascus steel chef knife 8" yaxell but i cant get it factory sharp or even more...i do all by the book but its not getting sharp like i could shave hairs from my hand.... i am desperate

Are you hitting the edge?

How hard is it to force a patina on the clad iron in that ITK?

NO ChoP! said:

Are you hitting the edge?

Click to expand...

i guess i do..im getting a burr

They are inexpensive knives, but with a little work they can be decent. "With a little work" seems to be the sticking point at this price point. There seems to be an onus about CKTG, but the Goko 240 gyuto in 19C27 damascus is a great bang for the buck knife. I got one last week and after a trip to the stones it's a very good performer.