Gun bluing Carbon Steel Kitchen knife?

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XSanguin8

Joined
Mar 31, 2007
Messages
260
Hi all,

I have an old vintage high carbon steel knife I've been using in the kitchen that I really like for cooking. It's very sharp, and is a good all around chef knife.

The thing is, it's stained, and kinda ugly. I was thinking about bluing it along with some gun parts I was going to do anyway. I have seen other knives that were gun blued, and I liked the look.

I'm wondering, would this be bad for a blade that would be used for food?

The bluing is a controlled rust, and the chemicals used should wash off after, but I don't really know for certain.

Can someone WHO ACTUALLY KNOWS, AND ISN'T JUST GUESSING, please chime in?

Thanks in advance. :)
 
It can be done. My concerns would be:

1. Are you going to remove the scales? If not, how will you prevent the salts from impregnating them or getting between them and the steel? Any salts left in the scales will continue to eat away at the materials (including the steel) and eventually ruin your knife.

2. How are you going to prep the knife steel? The discoloration will have to be entirely removed to take a good blue. For re-blueing, or preping bare steel, I usually use a blast tnk to clean everything, then successive polishing (preferably at 90 degrees from the last). The higher the polish the better the blue.

3. What blueing method will you use? Hot tanking is faster, but you get a black color and I really don't like the idea of eating those chemicals. Slow rust blue is more tme intensive and still uses some toxic stuff.

4. If you remove the scales you're going to have to be very careful refitting them. You will have polished the steel (removing material) and they will need to be fit exactly so as not to have high points. Polising or reworking them once they're on the steel will remove the blue unless you're very good.

I guess what I'm saying is why worry about the patina? You'd do better (if it bugs you) to just polish the knife out to a high (bare) finish. Remember, the better the finish the easier it is to keep clean. A mirro finish will take a long time to develop a natural patina if properly cared for.

I've blued countless guns and parts; I was a professional gunsmith for 15 years. Here's one of my kitchen knives that;s over 100 years old and still working.
bdc8433a-ac68-486a-a08f-41b74214f45c_zpsc65df64a.jpg
 
eisman, you make some good points. I was considering just covering up the scales, and just doing the blade. I was going to use a cold process that wouldn't require the use of a hot tank.

The knife in question has more discoloration than the knife you posted! It doesn't really matter I guess, I was mostly just thinking of doing it for gits & shiggles. :-)

Thanks for the response, and the cool knife pic!
 
knifenut-

what is the process of using lemon or onions? I've cut both of those in the process of cooking, and I didn't notice any different reaction.

Can you expand on this?
 
The natural acids in them will patina a blade, cutting up a side of beef will do the same. To force a patina with a lemon I usually heat the blade under hot tap water then rub the lemon on the blade. Let the juice sit on the blade until it cools a bit then rinse under the hot water and repeat. After about 10 minutes of doing this the blade will start to form a nice even gray patina.
 
Is it really necessary to remove the scales? Couldn't you seal up the parts you don't want touched with nail polish? I only ask since nail polish is the go-to with acid etching a folder blade.
 
XSanguin8 said:
Hi all,

I have an old vintage high carbon steel knife I've been using in the kitchen that I really like for cooking. It's very sharp, and is a good all around chef knife.

The thing is, it's stained, and kinda ugly. I was thinking about bluing it along with some gun parts I was going to do anyway. I have seen other knives that were gun blued, and I liked the look.

I'm wondering, would this be bad for a blade that would be used for food?

The bluing is a controlled rust, and the chemicals used should wash off after, but I don't really know for certain.

Can someone WHO ACTUALLY KNOWS, AND ISN'T JUST GUESSING, please chime in?

Thanks in advance. :)
Click to expand...

I would pass on the bluing, it will impart a bad metal taste to your food.
Many years ago in my youth as a Gunsmith apprentice, I was taught the blue finish
is like a sponge, instead of holding water it holds oil and the byproduct of bluing was a good looking finish.


I should add,
Bluing a kitchen knife is like rusting your knife then cutting food with the knife that has red rust covering the blade then deciding you don’t like the color red and you find away to change the color from red to blue/black, you have the same rust just a different color.
 
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NDtreehugger said:
I would pass on the bluing, it will impart a bad metal taste to your food.
Many years ago in my youth as a Gunsmith apprentice, I was taught the blue finish
is like a sponge, instead of holding water it holds oil and the byproduct of bluing was a good looking finish.


I should add,
Bluing a kitchen knife is like rusting your knife then cutting food with the knife that has red rust covering the blade then deciding you don’t like the color red and you find away to change the color from red to blue/black, you have the same rust just a different color.
Click to expand...
Not quite.

http://www.finishing.com/95/49.shtml

Black Rust on steel or Iron is Fe3O4. The red rust you normally see is Fe2O3. Black Rust is protective in nature as it's molecules are not as large as Red Rust. Black rust will coat the iron/steel and prevent oxygen from reaching the underlying metal. Red Rust on the other hand puffs up because of it needs more room than in it's previous unoxidized state. This expansion exposes bare metal to oxygen and causes the Red Rust to spread.
Click to expand...
 
I dont know,

I would think if you take some red rusty steel and toss it in a pot of boling water, something strange could happen.

Sometimes too much thought and too much google = the same, wasted time.
 
ebrguy said:
Have you considered Parkerizing it?
Click to expand...
That's dipping it in Ferric Chloride solution right? Sounds like the resulting oxide layer would be thicker and more durable. I have some solution available, but I wanted to get a few blades ready first so I can do them all at once;).
 
Parkerizing is a zinc or manganese phosphate process. It grows a fairly thick layer of very porous material on the blade, I do NOT recommend it for food prep blades at all. Cleanup is a PITA with that kind of surface. Cold bluing works fine, but make sure that you clean off the bluing solution completely before using it again for food prep, as the chemicals in cold blue are rather toxic. Also be aware that cutting acidic foods like onions pineapples or apples will often react with or remove a cold blued finish. Best to just let the patina form naturally.
 
I have never seen a cold blue product that maintains any kind of longevity as a finish. Even unused over time the cold blue will just fade away.
 
Another ex gunsmith here - forget about cold blue on a kitchen knife. It stinks (rotten egg smell) and will wear off very quickly while providing almost zero protection and will taint your food. All of my kitchen blades are carbon steel and I simply let them form their own "patina". Once in a while I might apply a Scotchbrite pad to a nasty looking blade. If kept fairly polished the steel will be more resistant to corrosion. But as for bluing or Parkerizing - on my guns , yes. On my knives, never. Cold blue is nasty stuff. (useful, but nasty) A thin natural "patina" is a beautiful thing.
 
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I have never seen a cold blue product that maintains any kind of longevity as a finish. Even unused over time the cold blue will just fade away.
Click to expand...

Not true. I can show you a knife I cold blued over 30 years ago that's still holding. I have a couple guns that have parts that were cold blued and still hold up also. Any kind of blueing reacts to the way the process is done, and the care it receives afterwards. Even the best blueing tends to fade although some can last centuries.

If cold blues are applied correctly they will do very well, the problem is that most people using them don't work with the materials and process enough to develop a really good blueing method. Still, a rust or tanked process is better.
 
Noctis3880 said:
Not quite.

http://www.finishing.com/95/49.shtml
Black Rust on steel or Iron is Fe3O4. The red rust you normally see is Fe2O3. Black Rust is protective in nature as it's molecules are not as large as Red Rust. Black rust will coat the iron/steel and prevent oxygen from reaching the underlying metal. Red Rust on the other hand puffs up because of it needs more room than in it's previous unoxidized state. This expansion exposes bare metal to oxygen and causes the Red Rust to spread.
Click to expand...

The chemistry is wrong and someone please tell me how a molecule consisting of 3 iron atoms and 4 Oxygen atoms is going to be smaller than a molecule of 2 iron atoms and 3 oxygen atoms. It's about the overall reactivity of the molecule. There's no easy way to describe it, you're into molecular orbitals, bonding theory and energy levels if you want to know the mechanism. While it's true that red rust "puffs up" and exposes bare metal, there would be little point in brushing the rust off to inhibit corrosion. Active red rust corrodes a lot quicker than just bare metal because there are additional corrosion reactions going on. The iron pillar at Delhi should be about the size of a needle by now (or double its size if rust didn't flake off) if corrosion was a simple chemical reaction, but in 1,600 years, the crystalline phosphate film has grown just one-twentieth of a millimetre thick.[
.
 
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eisman said:
Not true. I can show you a knife I cold blued over 30 years ago that's still holding. I have a couple guns that have parts that were cold blued and still hold up also. Any kind of blueing reacts to the way the process is done, and the care it receives afterwards. Even the best blueing tends to fade although some can last centuries.

If cold blues are applied correctly they will do very well, the problem is that most people using them don't work with the materials and process enough to develop a really good blueing method. Still, a rust or tanked process is better.
Click to expand...

Yes it is TRUE that I have never seen one that will.
 
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