Carbon vs Stainless Steel

knarfeng said:
You've taken the manufacturer's comments out of context. Then you make that crack about a well respected vendor's expertise. Poor form. And noted.

That's a steel manufacturer who talking about stacks of steel stored in a warehouse. That's a far different scenario from a polished blade which has been properly stored.

Unpolished and exposed, non-stainless steel is dull.
Polished and protected, it's every bit as shiny as stainless.
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Yes I agree that you can polish carbon to be shiny as stainless but even with it proper storing techniques it will eventually dull because of it's exposure to air. You can't say that company doesn't store it's steel properly in a warehouse without seeing it first hand. So to me it's not taken out of context as all knifes come from somewhere as I've seen people make them all sorts of things like ball bearings, leaf springs etc that were not intended to be knifes.
 
Mecha said:
FortyTwo, you're getting at what I was going to elaborate on next, in this and your previous posts. Firstly, an oxide layer does change the visual appearance of an alloy. So-called "heat anodizing" even makes metals change the spectrum of the rainbow due to altering the thickness of the oxide layer on the surface. Even the thin chromium oxide layer that forms on the surface of stainless steel, and probably the tiny chromium carbides themselves being a different composition than iron carbide, will scatter light ever so slightly differently than the same steel sans the high level of chromium.

If someone made a stainless steel-clad san mai laminated knife, where the whole knife was was polished evenly, I'm sure that there are many people out there who could say, confidently, that it was a stainless clad san mai, because the high chrome steel on the flats would look that much different than the high carbon core.

There is a whole art form to visually appreciating the minute details of grain structures, crystalline phases and varying carbon levels just within just carbon steel alone, in a Japanese sword. Within a polished sword, one can see which parts of the sword are martensite, pearlite, etc., and also which parts are high, medium, and lower carbon steel, or iron. The blade is observed very closely in good light, and various angles to observe the scattering of light from the steel's surface.

The tatara smelters and sword smiths themselves, visually and through feel, accurately evaluate the purity, quality, and general carbon content of the various pieces of steel before forging begins. If one were to slip a disguised piece of stainless steel into the sample box, the sword smith would immediately tell that the piece of stainless steel had a huge amount of some alien alloying element in it upon feel and observation. Why would he not be able to say that is was steel highly doped with chromium (stainless steel) after some practice picking out stainless? A HUGE amount of chromium should make reliably observable changes just as a tiny amount of carbon does.

With all this talk about science, I don't see the "science" behind the supposed impossibility of seeing the difference between normal carbon and stainless steels. All I see are some people stating it's impossible, and others stating that it is possible, with no "proof." I don't understand the strong motivation to believe the difference can't be seen and sensed.
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Again, I'm not saying that you can't see a visual difference. It's a matter of being able to accurately and consistently assign a label of "stainless" or "carbon" to different samples of steel by sight when in a state of bright finish. If you took 100x Opinel blades, with half being stainless and half being carbon, mixed them all together in a tumbler, and then had even a very experienced person sort them into two piles, with the piles scored on both the metrics of all the blades in a pile being the same kind and on correctly identifying which kind is stainless and which is carbon I think that people with a keen eye could do very well on the former task (sorting one type from the other) but only score statistically equal to the 50/50 chance they'd have randomly guessing which one was stainless and which one was carbon. Blindfold the person and it would be totally random in both tasks.

In laminated scythe blades I can very commonly identify the separate layers of steel and iron, and you can see a photograph of it at 7:24 in this video showing a laminated blade that was deliberately ground too much on one side, making the edge cladding iron. The ribbon of paler coloration in the blade is the high-carbon cutlery steel edge layer, while the cladding is high grade Swedish iron.


But if I didn't tell you what material was what, and the faint flecks of storage rust on the factory bevel were removed, you wouldn't be able to tell on appearance alone that none of those three layers are stainless. You'd only have the context of it being a vintage scythe blade etc. to give you that info. A cropped image with everything else taken out and other context removed, you'd just be able to tell it was laminated, and not really anything beyond that.

So, to reiterate, you can see that they are different from one another, but you cannot use that visual difference to reliably improve your ability to guess correctly above the average for completely random guessing. Two different carbon steels can look different from one another. Two different stainless steels can look different from one another. Some carbon steels and stainless steels could plausibly even have the same overall look to them in luster and tint. If you were to take a random spread of steels, carbon and stainless, and prepare their surfaces in the same fashion, and have someone match the names of the steels to the appropriate blocks, the results would possibly even be worse than random guessing. Does that clarify my position at all? :)
 
FortyTwoBlades said:
NO ONE disputes that once carbon steel has oxidized that you can clearly tell the difference. If you think anyone has said that, I'm afraid that you're gravely mistaken. But when surface finish is identical, they are barely distinguishable, and not to such a degree that even a skilled observer can reliably guess which is which by appearance.
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This is what we are talking about. Not steel in a warehouse.
Polished carbon steel looks just like polished stainless steel.
 
Gentleman! Slightly off topic! —-////—-At this time and date of the evening of 9/11 all This Knifemaker can say about this never ending controversy ;) of the issue of “Carbon Steel VS Stainless Steel” is God Bless the USA, and all of our first responders and all of the victims of that horrible attack that were killed & those survivors that live with horrible lung problems and nightmares & worst!———————-/////——————— Is that this knife Maker is thinking about you!!:thumbsup: Have a nice evening everyone!
 
FortyTwoBlades said:
Again, I'm not saying that you can't see a visual difference. It's a matter of being able to accurately and consistently assign a label of "stainless" or "carbon" to different samples of steel by sight when in a state of bright finish. If you took 100x Opinel blades, with half being stainless and half being carbon, mixed them all together in a tumbler, and then had even a very experienced person sort them into two piles, with the piles scored on both the metrics of all the blades in a pile being the same kind and on correctly identifying which kind is stainless and which is carbon I think that people with a keen eye could do very well on the former task (sorting one type from the other) but only score statistically equal to the 50/50 chance they'd have randomly guessing which one was stainless and which one was carbon. Blindfold the person and it would be totally random in both tasks.

In laminated scythe blades I can very commonly identify the separate layers of steel and iron, and you can see a photograph of it at 7:24 in this video showing a laminated blade that was deliberately ground too much on one side, making the edge cladding iron. The ribbon of paler coloration in the blade is the high-carbon cutlery steel edge layer, while the cladding is high grade Swedish iron.


But if I didn't tell you what material was what, and the faint flecks of storage rust on the factory bevel were removed, you wouldn't be able to tell on appearance alone that none of those three layers are stainless. You'd only have the context of it being a vintage scythe blade etc. to give you that info. A cropped image with everything else taken out and other context removed, you'd just be able to tell it was laminated, and not really anything beyond that.

So, to reiterate, you can see that they are different from one another, but you cannot use that visual difference to reliably improve your ability to guess correctly above the average for completely random guessing. Two different carbon steels can look different from one another. Two different stainless steels can look different from one another. Some carbon steels and stainless steels could plausibly even have the same overall look to them in luster and tint. If you were to take a random spread of steels, carbon and stainless, and prepare their surfaces in the same fashion, and have someone match the names of the steels to the appropriate blocks, the results would possibly even be worse than random guessing. Does that clarify my position at all? :)
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I understand your position and agree, generally, except that when observing similarly polished carbon steel and stainless steel closely, I normally see a more robust rainbow irridescent shimmer (light scattering) above the surface of the stainless, which I always attributed to the chromium content. Never until today, in this thread, have I heard that it is impossible to see this and thought everyone did.

The only reason I started sport-arguing at all is because a few members said they liked the look and feel of carbon, and were derided and generally treated like idiots for saying the two major steel types had a different look and feel that they could appreciate.

Two identical swords, one stainless and one carbon, will be different and I bet you a titanium blade that you, yourself, could accurately tell which is which. :]
 
knarfeng said:
This is what we are talking about. Not steel in a warehouse.
Polished carbon steel looks just like polished stainless steel.
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I don't even try on the freshly polished , but after 40+ years of cutting pineapple , the truth is revealed , TA-TAH ! :

 
FortyTwoBlades said:
After I reveal which Otter Messer blade is which steel in the evening, I have an idea for a better way to visually pose the question. I can set it up as a poll, once there's daylight for snapping the requisite images. :)
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Sounds fun and exciting, I’m game. It will be difficult because the metal normally has to be wiggled or in motion to see the play of light that lets one get a really good look at it.
 
Mecha said:
They taste different. Seriously, just put the damn knives in your mouth and taste them.

Edit: I just licked a 52100 knife and a 400 series stainless steel knife. Way different from each other.
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Oh God now everyone is gonna start licking their knives!!!!

Please be careful :( tongues and knives are not a good combo .
 
And if you can see a difference between stainless and carbon side by side...what if you were only handed a single blade. Could one tell which it was without a comparison piece ?

Just tested my GEC #43 carbon and my Buck Smokejumper CPM154. Both tasted the same but the carbon has a distinct aroma. Both were cleaned with alcohol first to remove any food residue. Carbon blade did have a patina though which may have affected things
 
Heirphoto said:
And if you can see a difference between stainless and carbon side by side...what if you were only handed a single blade. Could one tell which it was without a comparison piece ?

Just tested my GEC #43 carbon and my Buck Smokejumper CPM154. Both tasted the same but the carbon has a distinct aroma. Both were cleaned with alcohol first to remove any food residue. Carbon blade did have a patina though which may have affected things
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That’s the million dollar question, Hierphoto.
 
https://en.wikipedia.org/wiki/Organoleptic

Organoleptic Analysis , although subjective and requiring some experience , is useful in many fields , including medicine and public health .

For most of history , that's all we had (our biological ,physical senses ) to use even for metal working . ;)
 
Yonose said:
What are you thinking of that has come close? I would love to try it. 12c27 is tough, but not that tough! S7 has 3.3% Chromium and is probably the toughest steel used in large knives or swords. I don’t know whether the chromium gives the steel any stain resistance—I have to keep mine oiled after use in the humid summers. D2 is perfect for a folder, but I also like high vanadium stainless in small blades.
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I would also like to know what stainless steel has a toughness close to s7 or 3v.
 
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