Is this a brown patina or rust ??

Hello guys !! I'm new in the world of japanese knives, and finally invested in 2 masakages for home use: A nakiri and a guyto. The guyto is from the shimo line of masakage, which is known to have a very reactive blade. I thought "no problem" because it's for home use and I'm used to care for carbon knives, before the masakages my go-to knife is a carbon sabatier, fact is.. the shimo is WAY more reactive than the sabs. And today it developed some sort of brown colouring, which I'm not sure if is rust or just patina. I've been cutting tomatoes, cherry tomatoes, red onions, lemon, potatoes and some fresh cheese. After cutting each ingredient, if I would not cut the next immediately, the knife was passed under water, dried with a cloth and left on the cutting board (that had moisture). See the pictures, what do you guys think??

PS: Sorry for bad english .. really not my native language..

Looks like rust (orange and powdery) to me

That's rust.

"Orange-brown patina" = rust.


TTB, Ph.D. (Chemistry)

I don't have experience with that series of knives, but it looks like rust from what I can see. I have some Misono Swedish steel carbons (which are also said to be very reactive) and I got sort of a gold color that could look brown/reddish depending on the viewing angle and light source. This looks much more rust colored compared to what I've experienced with mine.

Wow !!! Thanks a lot for the quick reply !!! What would be the best way to clean it ? I tried with hot water and the soft part of a scotch brite dishwasher and it helped a bit, but did not completely removed it, the harsh side scratches the steel and I did not want to use it before asking to be sure.

Barkeeper's Friend or any of the metal polishes (Mother's Mag, Flitz, etc.) will work.

Thanks Rick ! I'm not sure it those brands are available here (Portugal), but it looks like regular metal polish (including automotive use), I'll go to the supermarket soon and see what I can find.

WD-40 works for removing rust from knives??

In Portugal, you should be able to find Autosol pretty easily....

LuisMendes said:

WD-40 works for removing rust from knives??

Click to expand...

In a way. It's not really a rust remover, but rather a water displacing solvent.

Any mild abrasive cleanser like Cif will work if you can't find Bar Keepers Friend or the metal polishes.

For what it's worth, I think that some of the traditional iron-clad knives are so reactive that they only really work for Japanese-style cooking. I have a Moritaka nakiri, which is a lovely cutter, but it only needs to look at a tomato to rust. If cutting wet or acidic products, you basically need to work with a dishcloth by the side of your chopping board and wipe the blade dry every minute or so. For dry ingredients, you can push it once you have built up a bit of a patina. But it's nothing like a carbon Sab.

I went to the supermarket because I knew it was open on a Sunday, and got nothing.. Came back home and tried with CIF, worked like a charm !!! Thank you guys a lot !!! The blade is like new !! :doublethumbsup:

What I do is create a slurry with a higher grit stone and then use a rolled up towel to wipe the slurry up onto the towel. Then use the area of the towel that has all the slurry on it to remove the rust. Wipe up and down the blade length wise and it will polish right up.

It definitely looks like rust. Flitz may help. Slurry from a high grit stone, too. If that doesn't work, try a dedicated rust eraser. And if that doesn't work, fine sandpaper.

2000 grit sandpaper will also have it looking like new.

@nicholls welcome to the forum