Carbon steel turns purple!

N

Nimravus Nut

Joined
Jan 17, 2003
Messages
202
I have been using stainless knives for a long time, but was interested in carbon steel for its ability to hold an edge and alot of praises from forums members. So I recently bought a Cold Steel SRK.

I didn't like the black epoxy coating so I put it on a belt grinder. Now it's got a nice polished "steel look". After I did a little cutting (apples), the blade surface started to turn purple, and there is literally purple apple juice dripping down the edge of the blade.

Is this normal for carbon blades? P.S. the blade smells funny. :eek:
 
Carbon steel does indeed smell "funny." Some of us like it... it reminds us of a nice knife. :D

And it does stain easily, especially if you let acidic liquids (apple or tomato juice, for example) sit on the blade for a hot minute.

Peace.
 
Welcome to the club!

I use stainless and carbon in the kitchen. The carbon does smell. The food tastes OK, though. :D

You can polish the staining off. Try any metal cleaner, or Flitz. Then go for a patina of your own, by dipping the blade in lemon juice or vinegar for a while, and taking it out and rinsing it in cold water once you've got the shade you like. Then it won't corrode again as easily.

I let my carbon blades take on a natural patina from whatever they cut. Most fruits and vegetables will do it, to some extent. It's like old leather, it gets better-looking with wearing.

You can polish it and keep it oiled to reduce staining, but frankly, heavily acidic foods especially are going to stain carbon steel eventually.
 
It also adds a taste to the food if you havent noticed. Iwas cutting an apple with my Opinel #8 and my GF saw that there was a thin bluish layer on the apple :eek: she wouldnt eat any of it but im pretty sure I'll be okay... although I do have this strange rash now... ;)
 
Well I just hope I don't set off the metal detectors when I go to the airport
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LMAO :thumbup: :D

Man, one of my favourite smells is Steel, prob why I like Guinness so much. :cool:
 
You know, I think it's vanadium that causes that. I've had O-1, and 0170-6, and (of all things) talonite do this to me, although the talonite didn't have any staining on the blade itself the goo on the blade did turn purple. For using carbon steel on fruits and stuff I advise cutting quickly and wiping the blade often, if I'm in the kitchen I'll just run a bit of tapwater on the blade and wipe it down whenever it's not cutting.

edit: to clarify I meant the strong purple color, not the blue/black that all carbon steels form. The purple stuff doesn't seem to be discoloration in the steel so much as the sap/fluid from what was being cut reacting with the blade and sticking really firmly. When I was out limbing some maple branches with an 0-1 knife after a storm some of the maple sap stuck to the blade and turned purple, in addition to the normal grey/black oxidation on the steel.
 
I have seen a carbon blade turn purple before. I was using a Khukuri to chop a green log and noticed the edge was turning purple. I picked up a fresh chip of wood and rubbed it on the blade and it "purpled". I thought it was pretty cool. It wiped off prety easily.
 
Now you know why the blade was coated. Some don't like the patina that develops over time wth high carbon steel. I do. On my hand made folders of 1095 and other high carbon steel I use a gun blue solution to turn them blue/black in color and rather like the even look of blued steel.
 
This is very informative.

So is it more advisable that a stainless knife be used for food prep chores? Save the carbon chopper for wood, brush clearing, but use the stainless for food?
 
In some tests done on D2 which is a high carbon non stainless and VG10 in every test the D2 outperformed the VG10 until acidic fruits and veges were cut. Then the D2 blade had obvious edge cutting reduced to below the level of the VG10 which outperformed the D2 by a fair margin once these things were cut. This would be much the same with any high carbon steel.

Another note of importance is that the vinegar bath, or soak, and the fruit cutting can degrade the edge on your knife also so in most all cases of doing this and even after I gun blue a blade the edge needs touched back up to bring it back up to par afterwards.
 
Temper said:
LMAO :thumbup: :D

Man, one of my favourite smells is Steel, prob why I like Guinness so much. :cool:
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When I take a shower after grinding all day, I smell like a wet piece of steel. :D
Scott
 
STR said:
In some tests done on D2 which is a high carbon non stainless and VG10 in every test the D2 outperformed the VG10 until acidic fruits and veges were cut. Then the D2 blade had obvious edge cutting reduced to below the level of the VG10 which outperformed the D2 by a fair margin once these things were cut.
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If you get a chance try a knife made from S90V. In my tests it out preformed VG-10 by 3 times!
 
Hi Chuck. I have heard that is one good steel. With all that carbon and vanidium it looks like it is a kick a$$ steel. Who is making anything using it thoug? I thought it was discontinued for some reason but that may be a mix up on my part with some other steel.
 
S60V has been discontinued. S30V and S90V are still being made.

I have three knives made from S90V. Coincidentally all three were made by Phil Wilson. I highly recommend Phil's work. He makes excellent knives.

Our testing process was making salsa. Tomato skins take the edge off knives surprisingly quick. With the Spyderco paring knife I usually dice about 24 cups of tomatoes before the edge starts to drag. I then touch up the edge on crock sticks. The Kershaw Shun with VG-10 does better than the Spyderco by about 25%.

The Phil Wilson skinner has a blade is almost three times thicker than the Spyderco so it did not slice as effortlessly as the Spyderco. After 48 cups of diced tomatoes the knife was still not dragging. I then prepared two boxes of peppers for the food processor and the knife was still sharp. Even my wife was impressed.

Since that test we've received a paring knife and a trout & bird knife both with S90V blades. The paring knife is super thin and cuts great. My wife loves using it.

The only downside is sharpening. It takes a long time to sharpen but I think it is worth the effort.
 
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