What Determines the Color in Acid Etch?

Was browsing through BST and saw Livlif's etched Miyabi.
Wow. Such an improvement over stock.
http://www.kitchenknifeforums.com/showthread.php/23288-Cool-Knives-For-Sale!-Fujiwara-Kotetsu-Miyabi
The muted damascus pattern was on the deciding factors against me picking up that Miyabi 600MCD I was asking about previously.
I didn't know this could be done.
I always assumed the dark colors on the Hattori KD and the Tanaka Ironwood blades were from the metals used.


That got me thinking, how come parts of the knife get dark, and other stay light?


Ran a search and came across Dave's 2 threads:
http://www.kitchenknifeforums.com/showthread.php/11803-Gallery-Hiromoto-AS-Full-Spa-Treatment
http://www.kitchenknifeforums.com/showthread.php/6474-Damascus-Knives-amp-Re-Etchng


From my recollection, the damascus patterns from claddings a secondary stainless with a higher nickel concentration?

So the nickel darkens?
And from the Hiromoto thread, it looks like the carbon steel darkens?
Can this be done with any blade to make it super dark?



Will this work on an Takamura Hana?

I can't comment about the processes, but My Takamura Hana was fairly dark ootb, whereas the Miyabi is more polished same with Sukenari (basically a mirror). Part of it may be the way it shows in a picture under certain lighting. I could upload a side by side pic of the three if it'll help for comparison but won't be able to for a few days

Nickel stays bright; steel darkens. A short time in ferric chloride will give you a light etch (figure frosted and shiny like a lot of damascus knives out there). As the steel continues to etch, it'll go from shiny to matte-whitish to gray and finally to black. The time it takes to go from shiny to black depends on a couple of things including steel type and temperature and concentration of the etchant.

Etching works with some knives and not with others. I've etched several stainless damascus knives with pretty decent success, but can't get a decent one on a Tanaka VG10 and Shimatani VG10.

I've played around with etching and to be honest, it makes the knife pretty, but I find that it gives the knife quite a bit of drag (at least when I've done it on stainless knives). I usually lightly buff my blades post-etch with some 0000 steel wool to mitigate this issue, but, in turn, that takes the finish from black to gray.

I know right? The darker blade color really makes that handle pop.

The color is decided by the iron oxides that form on the surface of the knife. There are 3 primary pure iron oxides that form (red, yellow, and black/deep blue). The thickness of the iron oxide layer and the oxidation state determines the color.

Isn't iron oxide rust?

Culverin said:

Isn't iron oxide rust?

Click to expand...

All "rust" is an iron oxide, but not all iron oxide is rust. Some oxides of iron are FeO, Fe2O3, Fe3O4. IIRC a patina on a carbon blade is (partially) a thin oxide layer

I had a look at my Hana santoku yesterday, turns out I was wrong about the darkness (must have been thinking about the ZK SG-2santoku instead), the Hana is not as polished as the Miyabi 600MCD, and also has a different pattern with more etching making it look darker.

Here are the pics I mentioned yesterday, you can see how they look slightly more/less polished depending on the angle.

James said:

Nickel stays bright; steel darkens. A short time in ferric chloride will give you a light etch (figure frosted and shiny like a lot of damascus knives out there). As the steel continues to etch, it'll go from shiny to matte-whitish to gray and finally to black. The time it takes to go from shiny to black depends on a couple of things including steel type and temperature and concentration of the etchant.

Click to expand...

ran some searches, didn't really see any hard and fast guides.

I guess like most things, start slow and work my way up?

tjangula said:

All "rust" is an iron oxide, but not all iron oxide is rust. Some oxides of iron are FeO, Fe2O3, Fe3O4. IIRC a patina on a carbon blade is (partially) a thin oxide layer

Click to expand...

Ahhhh, so that explains why the stainless parts on Dave's Hiromotos stay bright,
While the carbon part gets dark.


Thanks for the photos.
I already thought the Miyabi kinda bright for me.

I think I'm going to aim for the Takamura, but going to want to darken it.
Seems very silvery-"white" to me.

Nobody's ever etched a Takamura before have they?

Also curious how the red handled HSPS would take to etching.

I'm not sure how a mostly SS knife would respond personally, that said I've never tried it. Usually the Damascus layers are of various carbon steels and are perhaps semi or non stainless (although there may be some SS/nickel layers too?). My ZK Damascus has a warning on the box that it's not DW safe probably for that reason.

If you like dark Damascus check out this one from our Canadian vendor Tosho:

https://toshoknifearts.com/shop/knives/konosuke-blue-1-black-damascus-270mm-yanagiba-ebony-and-bone

This one from Murray Carter also looks pretty dark:

http://www.cartercutlery.com/5-87-s...grams/?page_context=category&faceted_search=0

Wow, that Konosuke is so dark!
I don't need something that striking,
That carter is gorgeous too.

Would be very happy if I can get something like that Miyabi Livlif posted.

Or like the Tanaka.

But because of price and handle, I'm really leaning for the Takamura.

When you etch a non-damascus stainless clad knife, the core steel darkens and the cladding changes color a little bit. Like so -

https://youtu.be/s7OEuhOn4-4?t=5m3s

In this vid, they are using Eastwood Metal Blackening Solution.

Video says it's a "copper-selenium compound"?

Anybody have experience with this?

Stay away from the blackening gels and liquids. They are a pain to get the metal evenly dark and they leave your knife smelling like rotten eggs. I've tried a couple different types and it was a waste of money. If you want to darken the Damascus cladding like I did on the Miyabi then just purchase some PCB Etchant from Radio Shack. All you need to do is rub it on with a toothbrush, let it sit for a few minutes, rinse with water, then wash with dish soap to neutralize the acid. Do this as many times as you want. Them more applications you do, the darker the Damascus will get. Hope this helps!

Culverin said:

https://youtu.be/s7OEuhOn4-4?t=5m3s

In this vid, they are using Eastwood Metal Blackening Solution.

Video says it's a "copper-selenium compound"?

Anybody have experience with this?

Click to expand...