Damascus Thoughts: Thinning Impact

[SilverSwarfer]

Browsing the BST I had a thought about hard use of aesthetically enhanced tools: what are my boundaries in considering use of certain beautiful blades?

I really love this Tanaka (Shigeki I'm pretty sure- correct me if not) 240 Gyuto I got in 2016. At the time I was rarely using Gyuto but this one struck me because it was presented as SG2 clad in SS. I threw it in my cart with a Tekeda "Super Yanagi" (really a suji I don't understand) I just had to have.

I didn't really start using the Tanaka until April 2019 and since then, I've done some thinning. Vast improvements resulted from the work I did in terms of cutting performance. This is now a very awesome knife! However, the aesthetics took a real beating. The grind is not perfect and neither am I. Eroding the original finish while thinning enhanced the imperfections of the grind. It's just a different thing now in terms of looks.

For me in my philosophy of use/ownership, I decided I can't specifically pursue certain aesthetic enhancements like Damascus. Highly polished or Kurouchi or Kasumi finishes all fit nicely with my knife needs. I enjoy maintenance of my tools and I have the capability to maintain excellent finishes. Many knives become more unique and beautiful as they evolve through years of use and scores of sharpening, polishing, and thinning sessions. Damascus IME/O is an exception: the more it erodes on the stones, the worse it looks. I am hoping for some contrary examples; I am always open to experimenting with new approaches to knife maintenance.

In this case thinning the Tanaka improved the tool at the cost of ruining the presentation. In consideration of the BST knife that spawned these thoughts, I have reinforced the realization that paying more for certain aesthetic features does not make sense for me: given I use every knife I own at work and sharpen/polish/thin frequently.

Aesthetics aside, how does a Damascus cladding, like in the case of this Tanaka, enhance a knife?

 

[ian]

In my experience, it's just aesthetic.

That said, from your post it seems like you think you ruined the finish of your knife irreparably. But if you want to, you can make it look nice again. It might be hard to restore exactly the original finish, but hitting it with some sandpaper to get rid of that darker look you got from the stones, and then etching it, will restore the contrast. Someone correct me if I'm wrong, though. I've only done this 2-3 times.

 

[SilverSwarfer]

It is far from ruined; it's just totally different. I am not bothered at all by how it looks. I have no thoughts of selling but the work I have done has certainly affected resale value of the knife.

As for restoration, I would say it's impossible because the original finish has a lot of texture. I'm sure an etch would increase contrast, and I might consider that if I ever have cause to etch anything else.

I still love this knife. Sometimes it wears a JNAT finish, which looks a little more organic.

 

[ojisan]

To be honest those pictures look good to me, probably because I don't know the original appearance of the knife?

I'm avoiding Damascus kives due to this exact reason you have. It's harder to refinish and keep looking good. It's better than KU in a sense though as a sand blasting tool and/or etching liquid can restore the original appreciate, but still it's not "easy".

It's just aesthetic and that harms the aesthetic value...

(If it's a single beveled knife and with a proper composition of suminagashi, the conclusion would be different)

 

[SilverSwarfer]

I agree with the single bevel comment, since the table is separated by the shinogi line. The Watanabe Yanagiba @nutmeg has listed in BST is a beautiful example.

 

[ian]

As for restoration, I would say it's impossible because the original finish has a lot of texture.

What do you think the texture is from? I'm assuming the knife has been ground all the way up to the spine (it's not a KU finish), so if there's texture, maybe it's just from a deep etch? Not sure how else one could make the different layers have different heights. Probably there are others that can tell me I don't know what I'm talking about, though.

 

[SilverSwarfer]

It’s a mystery to me. There are/were no grind marks. Also no hammer marks. The texture is a lot like forge scale though I don’t think that’s the case either.

 

[NO ChoP!]

It is from deep etch. Metals with different nickel content are used to create the dramatic effect. Ferric chloride will cause texture and contrast just like that. You can pick up a smaller bottle on Amazon for $10 or $15 dollars. It works like magic. After etching, a light sanding on 800 grit, or some 0000 wool will knock down some of the dullness and bring it back to gleaming ootb newness.

 

[tgfencer]

It is from deep etch. Metals with different nickel content are used to create the dramatic effect. Ferric chloride will cause texture and contrast just like that. You can pick up a smaller bottle on Amazon for $10 or $15 dollars. It works like magic. After etching, a light sanding on 800 grit, or some 0000 wool will knock down some of the dullness and bring it back to gleaming ootb newness.

Definitely the etch. Another example of this, although subtle, is Yoshikane SLD, which is textured in the black damascus area. I’ve got a scrap R2 blade I over-etched. I’ll try to get some photos later to demonstrate.

 

[ian]

Yea, I’ve only etched a couple Shuns, but even with quick etch you get some texture.

 

[drsmp]

Sand the whole blade to 1200-1500 , clean thoroughly and re-etch - should look great.

 

[ojisan]

I've been wondering if repeated etching causes hydrogen embrittlement. I heard some knife makers reheat blades after etching to remove hydrogen from them. On the other hand, I've never heard of any actual case that etching ruined a knife.

 

[lemeneid]

Use uchi finger stones then. Much safer if that a concern for you.

 

[krx927]

I have exactly the same feeling about damascus knives. They really look great until first thinning. After that it is just too much work to get them look nice. I also started to avoid them just because this reason.

Like others are saying, you can do it, nothing impossible, it just take to much time I am willing to spend regularly...

 

[Kippington]

I've been wondering if repeated etching causes hydrogen embrittlement. I heard some knife makers reheat blades after etching to remove hydrogen from them.

Very cool information, thank you. I was aware of hydrogen embrittlement, but didn't know it could be baked out of steel.

I've never heard of any actual case that etching ruined a knife

HE is one of those things you'll never know about until its too late. I'm just glad we're only talking about it in knives...

 

[suntravel]

Very cool information, thank you. I was aware of hydrogen embrittlement, but didn't know it could be baked out of steel.

needs 200° - 300° C for several hours....

Regards

Uwe

 

[Nikabrik]

When hydrogen is baked out after chemical milling, it's done around 375-400°F, according to one book on the topic. However, different steels show different susceptibility to it, and in many cases, it can be aged out at room temperature (8 to 33 hours, per the same book).

However, to my understanding that's mainly from pickup of H+ ions in acid etchants. Because ferric chloride isn't an acid, it wouldn't be worse that soaking in plain water.

 

[ian]

Because ferric chloride isn't an acid, it wouldn't be worse that soaking in plain water.

Really? Maybe I'm misinformed, but it's labeled as acidic online in various places. It also reacts strongly to baking soda, which I've used to neutralize it after etching.

I also thought acidity was the whole point with etching. I really don't know any of the chemistry, though, so I'm interested to learn.

 

[Kippington]

When hydrogen is baked out after chemical milling, it's done around 375-400°F, according to one book on the topic. However, different steels show different susceptibility to it, and in many cases, it can be aged out at room temperature (8 to 33 hours, per the same book).

Yeah I'm finding low temperatures in my search as well.
Considering that tempering of steel involves the movement of carbon atoms, it doesn't surprise me that the smaller hydrogen atoms require even less heat to diffuse.

 

[Kippington]

Really? Maybe I'm misinformed, but it's labeled as acidic online in various places. It also reacts strongly to baking soda, which I've used to neutralize it after etching.

I also thought acidity was the whole point with etching. I really don't know any of the chemistry, though, so I'm interested to learn.

I'm curious too. I've heard that ferric chloride is an acid, but Bob Kramer calls it a base in this video at 6:34. Whats the deal?

 

[Nikabrik]

Good call, guys.

It doesn't have any of the H+ ions associated with hydrochloric and nitric acids.

However, it does appear to form an acidic solution. I'm unsure at the moment if it causes H2O to split into H+ and OH-.

Both ferric and saline sulfate etchants are thought of as "metal salt" etches, as opposed to acids. I'm really curious to try the saline sulfate, as it looks sightly safer.

 

[Kippington]

...try the saline sulfate, as it looks sightly safer.

I used to get ferric solution all over my hands, it never bothered my skin in short exposures. I wonder how much damage it does in the long term?

 

[Nikabrik]

I used to get ferric solution all over my hands, it never bothered my skin in short exposures. I wonder how much damage it does in the long term?

Looking at the SDS, it's mainly "skin irritant", which isn't as bad as caressing nerve damage or dermatitis. However, some commercial "ferric chloride" etchants apear to include hydrochloric acid, so they're be a bit more hazardous. I know I see lots of Instagram videos of makers getting their fingers in the etch to pull out knives. I think at least some gloves would be a nice touch.

 

[suntravel]

Fe3Cl solved in water with about 40% concentration is Eisen(III)-chlorid-Hexahydrat (FeCl3 · 6 H2O) = ph < 1 , so it is an acid

But reaction on skin is minimal, because it can not solve fat.

Hydrogen deembrittelment on RT ? Never heard about that, on my main job steel parts with high hardness get after acid cleaning 3h 180°C an after galvanizing (more critical to hydragenembrittlement) 3h at 230° C. And this must be done max 24h after the treatment. Ist it would work at RT i could save lots of money and energy...

Regards

Uwe

 

[Nikabrik]

It appears that room temp hydrogen removal depends on the alloy. It worked for 4340, but not 301SS, for instance. I would guess that the galvanization would prevent release of hydrogen at room temperature.

 

[krx927]

Uf, this thread really took its own course...

Thinning Damascus remember.

 

[ojisan]

Sorry I didn't intend to hijack the thread, but great to hear opinions about hydrogen embrittlement from specialists. I just came across this topic on the internet and was curious how much it can affect the performance of etched knives in reality. A page I found at the moment said something like that he was not sure the actual damage by etching, but baked anyway his knives at around 200C for a while. Nothing was clear.
It seems there are a lot of parameters (steel types, mass/thickness, solution types, etching time, etc.) and hydrogen embrittlement is not visible, so I can imagine that it's very hard to tell...

 

[tgfencer]

Here’s a quick photo of a Yoshikane SLD. Tried to capture the texture, but obviously it’s hard in a photo. If I had to guess, I assume they etch the blade to the ‘black’ aesthetic and then polish the lower half, not completely unlike the way @SilverSwarfer knife now looks. I’m tempted sometimes to sand it all down and then re-etch as I don’t always like the texturing.

 

[SilverSwarfer]

Interesting post @tgfencer, I understand (obviously) what you mean. In my Tanaka, the texture is almost robust enough to actually snag terry cloth towels. Definitely erodes cheap paper towels.

overall I don’t mind the texture alone. While it was helpful with food release near the bevel, the knife moves through food better now that it’s thin and slick.

If you were going to re-etch, what would be your approach?

 

[tgfencer]

Sand it down to remove the black section, then sand it evenly throughout the blade surface, then etch in coffee or acid/base of your choice. The coffee etch method is slower and less corrosive then some others I've tried and I prefer that, but depending on the steel type and the coffee itself, results can vary. Probably won't ever do it though, saying it out loud sounds like a lot of work for something that is only a minor irritant.