Is this a crack in the hagane?

[noj]

The blade is from BST, used for one prep of (at home) potato salad, so wasn't put under any stress by me. It came "lightly" used, and had most of the tarnish removed.

What I see, now that some tarnish is present, is a roughly triangular piece in the hagane the with what looks like a hairline crack around it, and it's tarnishing differently. I don't see the pattern on the other side (yet anyhow). I don't see how it could be a scratch, given the steel it's in, what I used it for, and the shape. I can't get a better photo of it.

So, I am pondering ..

1. what is it?
2. safe to use?
3. should I sell it, and with what disclosure?
4. what did I forget to ask? ;-)

Thanks,
Jon

 

[stringer]

Do you see a crack at the edge? That just looks like patina to me but the photographic evidence is a little fuzzy. A crack would also go through to the other side so check the other side.

 

[Heckel7302]

Can you feel it if you run your nail across it? The photo just looks like patina to me.

 

[McMan]

No harm in cleaning with a little Flitz to see what it looks like once the patina is gone.
You'd be able to feel a crack with your fingernail.

 

[MSicardCutlery]

"Flitz it up!--Flitz it up!--Oh, oh ohhhoho........"

 

[natto]

Some veggie juices dry up pretty fast. Cutting a clove of garlic might fit the shape in the picture. The dried juice will stay during prep until the knife is cleaned. That can leave such discoloured spots with sharp borders.

 

[noj]

Here's what I did so far ..

1. Flitz - a generous amount, polished with several paper towels, and then a cloth towel
After this, I can still see a fine line around the area as before, but all the patina is gone.
I can't feel the line with a finger nail, or even the tip of a knife (I didn't press hard, obviously).
I can still see a blip on just one side of the edge bevel, and not the other.
2. Polished the hagane with a proper finger-stone
After this, the area is almost hidden, very hard to see.
3. Touched up the edge on a 3k grit, and natural. Two gentle swipes on a unloaded strop.
No visible issues on the edge, though it's not sunny today.
Cuts paper towel nicely, no pause around the area in question.

I am going to use it again, and see what it looks like in the "real world". Will post results after.

Thanks for the suggestions!

I hope my other knives didn't run away and hide after they heard the nice patina screaming in pain.

 

[noj]

After a bit of work on vegetables (nothing hard), the lines are back, in the exact same pattern and shape as before. There's less patina than I had, so harder to see, but no matter. There's a definite dark spot on the edge, exactly meeting the line. It looks like I might imagine would happen if an errant piece of the hard steel was embedded somewhere in the processing of the hagane. The different patina on the triangle in my photo (with a line around it) might suggest a difference in metal chemistry. I don't have the expertise to suggest whether it's the metal composition, or perhaps chemistry induced by the line. No vegie stain would leave a mark that wouldn't come out with Flitz plus fingerstone, at least not with how I take care of my knives.

 

[SirCutAlot]

Just try a flex test, then you will know.

SirCutALot

 

[noj]

Just try a flex test, then you will know.

SirCutALot

Thanks, and I am not 100% sure what you mean. I have applied pressure with my fingers and towel at that spot, and nothing breaks. If it moves, I can't tell, but I doubt it. It doesn't visibly reach the other side, so no real surprise.

I still suspect an errant piece of the hard steel was embedded somewhere in the processing of the hagane.

 

[Troopah_Knives]

Thanks, and I am not 100% sure what you mean. I have applied pressure with my fingers and towel at that spot, and nothing breaks. If it moves, I can't tell, but I doubt it. It doesn't visibly reach the other side, so no real surprise.

I still suspect an errant piece of the hard steel was embedded somewhere in the processing of the hagane.

Can you explain that last part a bit further?

 

[noj]

It looks like a triangle of metal that was pressed (and/or) semi-melted to the rest of the steel, and left a "line" around it. It tarnishes differently from the adjacent steel on the other side of the line surrounding it. It doesn't go through to the other side. Doesn't seem like a crack or scratch would behave this way.

 

[Troopah_Knives]

It looks like a triangle of metal that was pressed (and/or) semi-melted to the rest of the steel, and left a "line" around it. It tarnishes differently from the adjacent steel on the other side of the line surrounding it. It doesn't go through to the other side. Doesn't seem like a crack or scratch would behave this way.

Yeah maybe its a line from some sort of inclusion or composition change. although the shape is quite strange.

 

[McMan]

Or lacquer left? Try acetone, thoroughly. Then re-set with flitz. A little bit of residual lacquer can do weird things.

 

[noj]

I used finger stones to smooth it, so I doubt it's lacquer, but no harm in trying it. I don't have another explanation that makes sense to me .. yet. If it matters, it's a Fuji FM

 

[natto]

With my first carbons I checked clean knives to learn how patina developes. Some dark spots with clean borders developed after cleaning. The spots were covered with a tough and full transparent "laquer". Some hard scrubbing got the laquer off, and left discoloured spots. And new laquered spots popped up after that scrubbing.

Some veggie juices dry up pretty fast. Cutting a clove of garlic might fit the shape in the picture. The dried juice will stay during prep until the knife is cleaned. That can leave such discoloured spots with sharp borders.

I have to admit, it is worse. The "laquer" can last repeated cleaning. From that experience I like the rough side of kitchen sponges much more. The patina became stable.

After a bit of work on vegetables (nothing hard), the lines are back, in the exact same pattern and shape as before.

Fingerstones touch the surface only, like a worn scrubby. This dicolorations can be deeper than your polish. The polish looks even, but can leave different textures. The next etch with foods will reveal the old pattern. That is common experience.

Grinding to clean steel will take off every discoloration. Touching up the edge will show wether rhe pattern comes back.

 

[noj]

With my first carbons I checked clean knives to learn how patina developes. Some dark spots with clean borders developed after cleaning. The spots were covered with a tough and full transparent "laquer". Some hard scrubbing got the laquer off, and left discoloured spots. And new laquered spots popped up after that scrubbing.


I have to admit, it is worse. The "laquer" can last repeated cleaning. From that experience I like the rough side of kitchen sponges much more. The patina became stable.


Fingerstones touch the surface only, like a worn scrubby. This dicolorations can be deeper than your polish. The polish looks even, but can leave different textures. The next etch with foods will reveal the old pattern. That is common experience.

Grinding to clean steel will take off every discoloration. Touching up the edge will show wether rhe pattern comes back.

Thanks for the feedback. I am reluctant to take an almost new knife, and grind the whole primary bevel. Maybe that's what it takes, but it opens the door to endless hours of work to get it looking good again.

I suspect knife vendors have a (low scratch) method that works pretty much all the time, and if so, repeated a couple times ought to be almost flawless.

 

[M1k3]

Use acetone/nail polish remover.

 

[noj]

Use acetone/nail polish remover.

I just finished that a couple times;-) I used a bit of Flitz in between. I used a few passes of acetone and fresh paper towel as I applied it to make sure the Flitz was gone, and I wasn't spreading around any coating material (if there was any).

What I think I can see now is a very very fine straight line going to the edge (looks like the left edge of the triangular bit in the photo). I call it a line, since I don't know what it is. I can't make out anything else. I think I want to just use it for a while and get a nice stable patina before I ponder more.

After all this, I may warm it up to something gentile before I hit the onions. It's so shiny, and stinks like iron;-)

 

[Blank Blades.]

Yeah maybe its a line from some sort of inclusion or composition change. although the shape is quite strange.

This is my bet. The picture is honestly not making it easy to tell though.

 

[hendrix]

…After all this, I may warm it up to something gentile before I hit the onions. It's so shiny, and stinks like iron;-)

Ouch!

 

[noj]

A quick update: I've used it enough to develop a nice patina (the iron smell is long since gone). The last workout was a huge bowl of potato salad, including a couple onions and pickles for a patina workout. I did a quick touchup of the edge, and I don't see the dark line, or any mark at the edge. As for the differential patina, I can't tell; there's a lot of streaking and colors and angular marks from all the push cuts through the celery and onions.