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View Full Version : moritaka 165mm petty vs fruit prep



jai
11-16-2012, 02:45 AM
so guys ive got a little situation that im unsure about, today i went into work with a recently purchased moritaka petty and decided to test it against the breakfast juice prep which involves about 20kg of oranges and 20kg or grapefruit + a bunch off pears, pineapples, apples, and watermelon. knowing that this blade is AS and carbon of course i knew what would happen slightly but wanted to see for myself. this is all on factory edge btw just didnt have the time to put my own edge on it until today after work as ive been busy. so basicly after about 10kg off cutting oranges for juicing the blade started to heavily patina, mostly dark greys slight blue tint to it, so i kept on prepping i should point out i was really giving this knife a workout. once i finally got onto the grapefruits it started to patina even more and it actually let off a really strong metalurgic smell and started to gain very dark brown colour im thinking it was just light rust but possibly patina. then the kuri ochi finish on the blade actually started to come off in spots and edge retention died a little bit not much but you could feel it dull a little maybe it was just because the oob edge was horrid or the acidity not 100% shure.

so after work i took it home took my rust removal paste and took the dark brown colouring off i managed to leave some patina and then i sharpening it up and stropped it and gave it a little test the edge is beyond anything it was before and the blade looks alright again but some off the kuriochi finish on the tip end is gone and alot off it is worn down.

now my real questions are, if i continue cutting citrus with this knife will patina form ok and if it does will this stop the metalurgic smell, or will it slowly eat the metal to much from my blade and cause continuous rusting. i am wiping the blade alot and washing it off through the whole process.

and before you ask why dont you just use a stainless petty well i have a decent stainless honesuki i love using for it but what im wanting to know is how my blade can handle the prep

ecchef
11-16-2012, 03:01 AM
Moritakas are weird. I have one that never rusts, one that gets a weird filmy patina, and one that rusts worse than an '82 Chevy Citation.
I used the boiling vinegar method (discussed elsewhere in this forum) with pretty good success.

jai
11-16-2012, 03:37 AM
If you have the time is it possible for you to send my a link for the thread with the boiling vinager method

ecchef
11-16-2012, 04:44 AM
http://www.kitchenknifeforums.com/showthread.php/7255-Hot-Vinegar-Patina?highlight=vinegar+patina

keithsaltydog
11-16-2012, 04:52 AM
I cannot speak for that knife in particular,however wt. most quality carbon just keep using it to cut everything.Because I worked Gardemanger quite a while cut lots of acidic fruits.Pineapple,grapefruit,oranges,lemons.That & about every other fruit like all the melons,strawberries,kiwi's etc.

With a new carbon cutting acidic items will dramatically stain your blade,just wash & dry it well so rust cannot get a hold.Also cutting everything,including protiens,a patina will form quickly.Once a good protective patina is formed,there is no staining or metallic smell.

When you put your own edge on your petty & get a good patina do not be afraid to use it.I can only say fr. my experience acidic items do not dull carbon blades.Extremely sharp carbon gyuto excell cutting tomato's & lemon wedges.We even used color coded plastic boards.

Dave Martell
11-16-2012, 01:16 PM
Mortitaka uses either mild steel or iron for cladding for the cladding of their knives and rather than leaving scale on the blade (kuriochi) they paint on a faux kuriochi finish. This paint on style finish can, and will often, peel off into your food prep and when it starts to go the mild steel (or iron) cladding begins to react and the stink starts as well as it (may) transfer tastes/smells to your food. This might stop and might not.

Thirsty
11-16-2012, 04:42 PM
Mortitaka uses either mild steel or iron for cladding for the cladding of their knives and rather than leaving scale on the blade (kuriochi) they paint on a faux kuriochi finish. This paint on style finish can, and will often, peel off into your food prep and when it starts to go the mild steel (or iron) cladding begins to react and the stink starts as well as it (may) transfer tastes/smells to your food. This might stop and might not.

Would you recommend removing this faux finish and creting a protective patina?

keithsaltydog
11-16-2012, 05:04 PM
I have not had many knives wt. this finish,I like mono carbons.I had an ITK Tojiro Santoku while trying to force a patina the coating started to come off,so I stripped all of it off,know it patina's like a non clad carbon.

Does anyone know why some forgers like to clad their blades,is it to keep down the rust,non stick surface etc.?

Timthebeaver
11-16-2012, 05:13 PM
Certainly not to prevent rust. Many carbon clad knives have jigane which is far more reactive than the hagane. Never recall anyone having unresolvable problems with monosteel carbons.

Cladding with soft iron (old scrap, chains etc.) is traditional. No performance advantage at all compared to cladding with soft stainless in my eyes, except it may be ever so slightly more user-friendly to abrade.

Dave Martell
11-16-2012, 05:16 PM
Would you recommend removing this faux finish and creting a protective patina?

I'd be concerned that this could go bad. In the case of Takeda knives this isn't advisable at all but I don't know about Moritaka.

Timthebeaver
11-16-2012, 05:22 PM
I think that stripping the kurouchi is a bad idea, unless its stainless kurouchi of course. The exposed soft iron would have to be polished to a high level of finish to prevent reactivity problems. If you are cutting mountains of citrus you're on a hiding to nothing.

Lefty
11-16-2012, 05:42 PM
They do it to cut costs, make it easier to grind, for them and us, and for traditions sake, if you ask me.

jai
11-17-2012, 07:36 AM
used the knife again at work and used it for other prep today such as capsicum, mushroom, onion and tomato.
it didnt react to mushrooms and the tomato was ok but the onion set off the bad smell again and it actually left metal colouring on the onion and the capsicum instantly gave the knife a brown colouring again but this time not rust.
didnt bother cutting the citrus and juice prep with it today just used my stainless honesuki. i like this petty and i am hoping that a patina can form and it doesent keep messing with my prep, it does hold a very stable and intensely sharp edge and its a pleasure to use. but i will keep testing it out when i can. just got put onto breakfast section for a bit because the other chef is off at the moment so hopefully once i get off i can test it out on some more veg in a more bulk test. thanks for the input aswell guys.