Tarnish or Patina and its Removal

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I cut some strawberries with my Wat Pro Nakiri and the edge reacted to them. It is now darkened but, after searching for and reading relevant posts, I don't know if the discoloration is tarnish or patina, what the difference is between them, whether it is desirable or not, and, if not, what to use to remove it (I have some Flit on hand). I have learned so much from you guys that this is always the first and sometimes the only research I need to do. Thanks.
 
It did not sit before wiping off. The color to me at least is dark bluish. My main concern is whether it--whatever it is--will dull the edge and therefore need to be removed. As to posting a pic, my mobility issues keep me from getting to the kitchen to take one but I will get one when my wife comes home for lunch.
 
I cut some strawberries yesterday with a CCK. My Mazaki petty did a lot of Strawberry Duty, as well. Almost instantly black, but still smooth to the touch. As someone who cuts lots of them for a 2 and 7 year old, its fine as long as it does not sit for long. Aesthetically, you may not like it, but it will not pit.
 
Acids will dull the edge, but that does not sound concerning. If you wipe the blade, with a clean, white cloth, does anything come off on the cloth?
 
Acids will dull the edge, but that does not sound concerning. If you wipe the blade, with a clean, white cloth, does anything come off on the cloth?
Nothing comes off. I have been furiously striving to become proficient to take any of my Japanese knives (all three of them) to the stones by the time they need it. If they need sharpening or a touch up it would be a toss up whether I would improve the edge or not. I would be comfortable with them on high grit stones such as an 8k.
 
You don't want your knife to look like this:

109912-20210326-194642.jpg


That type of orange has a flakiness to it that means bad rust. If you do see flaky orange, you want to address and clean it as soon as possible.

Aside from that most color you'll see on the core steel is fine.
 
You don't want your knife to look like this:

109912-20210326-194642.jpg


That type of orange has a flakiness to it that means bad rust. If you do see flaky orange, you want to address and clean it as soon as possible.

Aside from that most color you'll see on the core steel is fine.
Hopefully none of them will ever be as abused as that knife must have been. As long as the discoloration will neither pit nor dull the edge I have no problem with it.
 
Somebody far more experienced with patinas commented that their favourite way to force a patina is to use strawberries! Probably just a naturally strong reaction with those.
 
I'm sure someone has noted it, but I use crocus cloth which has fine iron oxide particles to clean up blade patina when it has stains or more severe rust (to a point.)

I have also resotred a lot of Sabatier knives from Europe in the last year that were well used and had some more pronounced rust. Crocus cloth doesn't deal effectively with thicker rust in any reasonable amount of time.

I don't see crocus cloth sold in hardware stores around me anymore. Don't know why. "Salesmen" have no idea when I ask as they just point to their fine grit aluminum oxide sheets as what I should use. Garbage recommendation.
 
You don't want your knife to look like this:

109912-20210326-194642.jpg


That type of orange has a flakiness to it that means bad rust. If you do see flaky orange, you want to address and clean it as soon as possible.

Aside from that most color you'll see on the core steel is fine.
Yikes! Is that a Watoyama? How did that happen?
 
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