Dark, but smooth spots on Shihan A2

[justaute]

All,

Any idea what these dark spots are? It's my Shihan A2 gyuto. Thanks much.

 

[Bico Doce]

No clue but the banding on this looks really cool

 

[Heckel7302]

Were they always there or did they appear later? Maybe ask Shi.Han?

 

[esoo]

I've always just assumed they were patina as they've come up during use on mine

 

[ethompson]

Looks like the start of pitting to me.

 

[superworrier]

Did you cut bananas or something?

 

[Troopah_Knives]

Look a lot like pitting to me. I'd remove it just to be safe.

 

[Choppin]

I'd try some Flitz or stone powder/mud and see if they disappear... then notice if there's any shallow spots left, then it could be pitting

 

[ModRQC]

My former Shi.Han 52100 had a tendency to do the same as is and without particular exposure or being left dirty. Once I put the first polish on it though, and from then on with such more or less regular maintenance, it behaved "normally".

 

[justaute]

Did you cut bananas or something?

Nope. I usually use my teeth or MAC knives.

 

[justaute]

Appreciate all the feedback. I'll reach out to Shihan.

 

[Neutri]

What's pitting?

Did you reveal the banding yourself?

 

[superworrier]

My former Shi.Han 52100 had a tendency to do the same as is and without particular exposure or being left dirty. Once I put the first polish on it though, and from then on with such more or less regular maintenance, it behaved "normally".

Etched?

 

[justaute]

What's pitting?

Did you reveal the banding yourself?

No. That's Shihan's original work. The banding only becomes prominent under close lighting and angle..

 

[Neutri]

Oh i just ordered one from him in A2. Can't wait to see that banding then

No. That's Shihan's original work. The banding only becomes prominent under close lighting and angle..

 

[ModRQC]

Etched?

Nope didn’t need to.

 

[justaute]

Got her back from Shehan. Decided to send it in to Shehan for re-etching in that I also had some scratches on the other side. Now it looks great again. Shehan is the man for doing great work with a quick turnaround.

 

[dehory]

What did he say those dark spots were?

 

[justaute]

What did he say those dark spots were?

He wasn't exactly sure, but did think it was likely very slight oxidation. He lightly sanded the blade before re-etching.

 

[Dhoff]

Cutting banana question a standing joke or?

 

[superworrier]

Cutting banana question a standing joke or?

No sometimes I get weird patina from it

 

[justaute]

No sometimes I get weird patina from it

I'm guessing it's the tannic acid.

 

[deltaplex]

I'm guessing it's the tannic acid.

They're essentially sugared edible acid paste and they'll 100% let you know how reactive all the steels in whatever you cut them with are.

 

[Dhoff]

They're essentially sugared edible acid paste and they'll 100% let you know how reactive all the steels in whatever you cut them with are.

Ahh I suddenly understand why i got instant small orange spots even after washing.

 

[Dhoff]

Should this be removed? It does not leave marks when drying

 

[Corradobrit1]

View attachment 230884

Should this be removed? It does not leave marks when drying

Knife Pox. Banana residue is pretty sticky and persistent. Are you rinsing thoroughly with warm/hot water?

 

[Dhoff]

Knife Pox. Banana residue is pretty sticky and persistent. Are you rinsing thoroughly with warm/hot water?

Not enough clearly. Probably the temperature.

Is it safe to leave or should I do something?

 

[mengwong]

I’d try rust eraser, but I am known to not care if my knives get scratched.

 

[More_Gyutos]

I’d start with baking soda slurry, then Simicrome or Fitz polish.

 

[captaincaed]

Rust erasers are pretty abrasive. Starting with a polishing paste may be a good way to start