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 Post subject: Patina Turner
PostPosted: Mon Jun 30, 2014 3:48 am 

Joined: Thu May 29, 2014 8:38 pm
Posts: 684
Being a home cook, I don't process a silo-full of a given ingredient in a night, and as such, having a massively reactive blade like a Masakage Shimo presents a bit of a problem. The matte iron cladding reacts to many ingredients so heinously, that it can cause the product in question look to like it was pulled across a filthy grill top, and the knife itself appear as if it doubles as a trowel during the day. Not to mention the nasty boiled blood/raw iron smell the thing emits during minor oxidization... While it probably wouldn't take more than a week or two of daily use to break it in, the patina it takes on 80% of the ingredients I use daily is foul.

To that end, I decided forcing a patina was the only way to go. Darkhoek's method was referred to me, and I tried it with decent results. The patina wasn't completely foul looking, though began to develop in a gross direction. So, I decided to try using hot proteins based on Darhoek's assertions about patinas and evaporation and the anecdotal evidence abound on forums about blueish tints forming through exposure to proteins. The results were mixed, and with the particular finish on the Masakage, it seemed as though avoiding a minor rust patina on the exposed iron grain was unavoidable. So, I put my Art History Major and Google skills to the test and the following is what I've come up with:

My guess is that because amino acids (assuming it is aminos that cause the protein blue that people are familiar with) don't achieve a fluid state until a very high temperature (400F - 600F), they may bind to, but not coat, the exposed iron grain as fast as other reactive agents that have a lower melting point. I'm completely pulling this out of my ass, but seems to make sense and explains why prolonged protein work over a long period of time, with constant blade wiping, results in amino induced patina. Once a a reactive agent reaches melting point, it is now a liquid that will completely coat an exposed surface. However, because it is a liquid, it is also easy to remove from larger grain surfaces. Non-liquid agents won't coat a surface, and thus have less chance of causing a reaction through initial exposure when introduced alongside a liquid agent. That said, they aren't removed as easily (no idea what the binding properties are of aminos or other acids in any state, so could be complete BS assumption).

This, I believe (though reserve the right to be stupendously wrong here) is where darkhoek is mistaken in his analysis of patina formation and evaporation. When the blade is hot and other reactive agents like water come into contact with it, those agents will evaporate preventing reaction. Agents like amino acids with melting points that are even higher than water's boiling point will be the only substances left for the iron to react with. In short, it is not evaporation that causes the formation of a patina that isn't basically rust, but the fact that rust-like oxidization is prevented b/c moisture is eliminated through conversion to gas, only exposing the blade to the remaining fluid or solid agents.

Long story short, I think if I can basically bring a protein rich ingredient like chicken or beef to a uniform temperature above 100 deg. C (probably closer to 200 or 250 deg. C to prevent moisture in the air from reacting with the blade in short order) and expose it to the blade for a decent period of time, the desired result can probably be achieved.

How stable a patina like this will be is anyone's guess. Might have to bring the temperature up to bring the aminos past melting point to achieve full coverage of the patina, but either way will update with pics and performance tomorrow.


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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 4:07 am 

Joined: Wed Feb 20, 2013 2:22 am
Posts: 562
Look out for temper embrittlement as you get around 400F. Hot tap water is the hottest I would ever allow a knife to see.


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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 4:25 am 

Joined: Thu May 29, 2014 8:38 pm
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Yikes.. Very good advice which probably averted a costly mistake. I'm guessing though that given the exposure to an indirect source that is gradually cooling, hotter than tap probably would be OK as long as the blade isn't heated up quickly and rapidly cooled no? Again, could be far off base.
So seems like the course of action will be to take the produce to 400F, assuring elimination of moisture, let it cool to 200F and apply.
Thanks again though as it would've been really unpleasant to warp or weaken/embrittle a knife like that.


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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 5:06 am 
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I did read everything you just typed, but still don't quite understand it all, so I will just add this about tempering:

Most knives can be heated to well past 300 degrees with no effect at all on the temper. If anything it will only get softer, not brittle. Here's why:

When you quench a knife, it is at the hardest it will ever be after the quench. You have to temper to bring the hardness down, and even the most simple carbons temper at 375 and above for kitchen knives (300 is lowest and is really only considered a 'snap temper' for stress relieving purposes, doesn't really bring the hardness down.)

So when you hear a knife maker say, "I have this knife hardened up to X rockwell", they really mean, "I tempered this knife down to X rockwell."

That's all, as you were. :)

Love the topic btw.



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Shaun Fernandez

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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 5:11 am 

Joined: Wed Feb 20, 2013 2:22 am
Posts: 562
I was considering using Mark Lee's Express Blue #1 on a knife but never got around to it. Maybe you could be the guinea pig?

You will need to submerge the blade in boiling water for a few minutes which should be fine.

Cheers,

Rick


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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 5:15 am 

Joined: Wed Feb 20, 2013 2:22 am
Posts: 562
Shaun, are you talking Fahrenheit or Celsius?

Also, a good read:

https://www.brownells.com/userdocs/learn/bt002006.pdf


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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 12:21 pm 
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Location: CT
I used a nice rare roast and put the blade in the middle of slices and let it sit for a few minutes. Nice blue patina! Or you can do an acid etch ( I use ferric Chloride, others use vinegar), which will give the blade a more matte look and make the patina more subdued. Often times with the rare roast patina method, when the blade is wet with juice/blood, it doesn't have much patina. Then I wash it with hot soapy water and then dry it with a paper towel. After drying with a paper towel, the Patina still changes slightly and then seems to stabilize after it's fully dry. But the blade looks completely different when wet with juice or after the juice is wiped off compared to when it is fully dried. I reground a few Kono Fujiyama's and the cladding was VERY reactive, so I did an acid etch on then blade. Brought out the core steel more and the contrast in the layers and the patina was more subdued after that and not quite as reactive.


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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 12:45 pm 
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Fahrenheit, of course. :) And good article.

It is true, there is a spot in tempering that you lose a lot of toughness.

Here's fun video with an Irishman that I watched a while ago, and he talks about spring steel and the color "BLUE"!



Many blacksmiths temper and forge by eyesight. Steel certain color = certain temperature. Close to 600 starts turning steel blue, but it's still brittle. Go a little higher and you get a much deeper blue, and then the steel returns to a much tougher springy state.

For kitchen knives (on carbon steels) we typically temper anywhere from 325 to 425. (For carbon and simpler steels, exotics work at much higher temps)

There a sweet spot on 1095 right at 325 degrees for toughness, but honestly that's still a bit too hard IMO. I've put a hard blade like that through its paces on a few hunting knives and it will micro-chip when you get into any kind of heavy work. The extra harness can actually negate the extra toughness in some cases, so you need to temper into the 400 degree range sometimes. All depends on the grind, how well you normalized the steel beforehand and how well you tempered it. You need at least 3 hours of temper on a blade with a break or two in between at some point to achieve a good temper. There's a balance of hardness to toughness that we are always looking for, but typically in the kitchen world so much toughness isn't needed, so we opt for the harder end of things normally.

No more about tempering, I didn't mean to hijack the thread lol :D



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Shaun Fernandez

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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 1:31 pm 

Joined: Thu May 29, 2014 8:38 pm
Posts: 684
No, good stuff! So, it sounds like exposure to meat below 300F should be pretty safe in terms of not impacting the metals attributes. Just re-read what I wrote earlier and apologize for the disjointed explanation. What I was getting at is that, unlike what gets propagated, commonly, it isn't the act of evaporation that causes patina formation. In fact, amino acid compounds wouldn't even reach melting points until temperatures got much hotter than most knives are even exposed to, so they are not evaporating on contact with a blade. The reason hot blades and produce seem to give better/quicker patinas is because moister is being evaporated, preventing the formation of iron oxide and allowing other reactive, non-corrosive agents (that have higher melting and boiling points) to affect the iron. In the absence of heat, amino acids will remain solid while water molecules will be in a liquid state (melting point is 32 deg F) which causes water to more easily cover the surface area of iron especially if the acids in question have low levels of solubility.
It gets a pit trickier than I initially thought however as dry amino acids may not not react chemically with the iron. The key, which Tim and others experience with blood or meat juices seems to be getting a solution that contains high levels of amino acids in contact with the iron. So, because aminos won't evaporate at the low heats that water will, heating a blade at or past 100 deg. C, and applying the amino containing solution (blood, juice from a roast or chicken etc.) to the hot blade in thin layers should allow the aminos to react to the iron while quickly evaporating water.
So Rick's suggestion of sticking a blade in boiling water, then applying protein juice may be the way to go. Will try it a little later today


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 Post subject: Re: Patina Turner
PostPosted: Mon Jun 30, 2014 2:07 pm 
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Good stuff, I hope your results pan out as suggested! This would be a cool addition to anyone's "patina arsenal."

Banana peels, cooked meat, mustard, vinegar, coffee grinds, and now heated blade on proteins?

Get that blade boiling! We need results back at the lab (forum) asap! :mrgreen: :mrgreen: :mrgreen:



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