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 Post subject: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 3:29 pm 

Joined: Wed May 02, 2012 1:08 am
Posts: 29
I own a couple Tojiro Shirogami knives in White Steel-7" Santoku and 120mm Petty knife. Indeed they are ridiculously sharp and keep their edge well. I'm a prep chef/line cook...I use my knives a lot.

Yesterday was a huge prep day. Lots of stuff to make for a busy event filled weekend at work. After mincing a ton of shallots, kale, and capers (I hate capers), the blade took on an ugly patina. Not that I much care about that, but as I wiped the knife blade between jobs, a significant amount of "stuff" kept coming off...it was like it was kind of rusting in my hand as I was using it. Even after washing and drying...I can hear rust growing on this thing while it is in the block.

Now I know this is nothing toxic or weird but is does not look all that presentable while cooking. I have tried to force a patina on this blade using all the common methods-mustard, vinegar, horseradish, etc. to no avail. The kurouchi finish wore off this blade really fast. I have never used anything rougher than a Scotch Brite pad to clean it, and that was only when food build-up necessitated it. The Santoku finish is basically gone, but the petty knife finish is still fine. (which incidentally does anyone know how to restore if I were so inclined to do so?). I'm thinking of trying "Cold Blue", a chemical used often to restore worn bluing on gun parts; I'm not sure if that would somehow result in a "toxic" effect (although I'm pretty sure it wound not as the oxidizing chemical is washed from the blade at the end of the process).

Point being...what exactly is going on with this blade? I'm close to retiring these blades to exclusive home use just because if I cannot remedy the issue. Any ideas or theories?


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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 4:21 pm 
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Joined: Thu Apr 26, 2012 5:13 pm
Posts: 2963
Location: CT
I don't think most Cold Blue would be good around food? Carbon steel will react to food until the exposed steel has finished reacting. Some knives settle down quicker than others. Sometimes I use a carbon blades on onions and it makes the onions look brownish and wipes off brown on a towel. I believe it may be the juices reacting and being discolored?? I had a 210mm ITK that I reground completely and took off all of the KU finish and left it at like a 400 grit belt finish. It would react, but not as bad as yours did?

I have had good luck with a forced meat patina. Cook a roast, slice it with the knife and make a sandwich with the knife. Slices of rare roast, blade, more roast slices on top of the blade and let it sit a few minutes. Remove and clean and you should have a nice blue/purple/gold patina. I've done this to a few knives and it pretty much stopped the reactions I was seeing. But I cook less than you do, so I'm not sure how that patina will hold up in a pro environment?

Are you getting red rust coming off or a brown/gold residue?


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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 4:29 pm 

Joined: Wed May 02, 2012 1:08 am
Posts: 29
Kind of a reddish-gold actually. You could call it sort of "auburn" colored for lack of a better term


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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 4:36 pm 
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Location: CT
Hmmm. When you wipe it off, do you dry it completely or is it left slightly damp? I dry my carbons off and then re dry them with a paper towel and let this sit out for a while before I put them back into the block so any moisture can evaporate off. Maybe try having the blades bead blasted? This may seal up the pores of the metal a bit more and reduce how much it reacts?


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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 5:12 pm 
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Joined: Wed Apr 25, 2012 2:55 pm
Posts: 473
I don't think it will ever get better for good.

In a pro setting, the patina will get stripped repeatedly, leaving you back at square one.

It isn't the white steel that is doing it, it's the cladding--it has so many impurities that it's super reactive. It is part of how they keep the cost down, and acceptable in many scenarios--yours is not one of them!

I would def replace them for work. Your health inspector may find it even more disturbing than you do, and it will sometimes discolor ON the food, which is no bueno.

This is the only reason why I didn't like to use my CCK at work.



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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 7:11 pm 
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It's weird that one of them won't take a patina and the other one will. We talked on the phone today and I was a bit stumped by this.

One thing you can do is oil your blade to keep it from reacting but that won't work during your shift since you will wear it off quickly as you cut and wipe. It will help you from opening up your bag the next day and finding rust on the blade.



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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 7:50 pm 
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Joined: Wed Apr 25, 2012 2:55 pm
Posts: 473
While it is possible that Tojiro used different steel sources for the cladding on different batches of knives(they probably take whatever they can find for that!), I think whatever different *jobs* the knives are getting used for is altering the patina. It can be surprising what can remove or set a patina when dealing with a professional setting. Cutting a few dozen pounds of mushrooms into slices will actually leave a patina, and a couple cantaloupes can strip a patina bare.

I just think that if it is an issue, (s)he will either have to live with it being a problem or spend a lot of time taking care of or managing them, which is totally not the point of a good knife in a pro setting. The best knife for your job is the one you forget exists--just works its ass off for you every day and you lets you focus on the food.



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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 9:34 pm 

Joined: Thu Jun 14, 2012 2:05 am
Posts: 110
have you thought about etching the blade in hot vinegar or ferric chloride?


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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 11:10 pm 

Joined: Tue May 29, 2012 12:29 am
Posts: 993
Any sort of etch or patina is a short lived fix for a carbon blade. Patina is not in any way a durable finish but just a oxidation of the metal, it's steels own way of protecting itself against red rust. Now don't confuse patina with a rust proof coating, it is not, it will only slow it down.

It may be surprising to hear but the way you sharpen the blade will affect how all your patina issues play out. Keeping the blade dry will be one of the biggest factors in this although it will not keep the patina at bay.

Though probably a good performer with a classic look it might be in your better interest to purchase a stainless replacement.


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 Post subject: Re: Tojiro Shirogami Blade Rust
PostPosted: Fri Oct 05, 2012 11:24 pm 

Joined: Wed May 02, 2012 1:08 am
Posts: 29
Well, we're trying the raw beef patina process and shall see how that goes.
Most probably I'll still be picking up a replacement (I also use a Tojiro DP...excellent performance and minimal maintenance) so I'm thinking I'll go that route. This is a superb home use knife as I can wipe it as often as needed. Maybe I'll just keep it at home or somehow part company with it. Not gonna toss it though; it still gets the job done...quickly.


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