The edge gets dull WITHOUT cutting?

Bill DeShivs said:
Could it be that the stainless is "passivating" itself at the new edge?
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I suspect that that is the case. Since stainless steel is basically self-passivating, the difference between passivation and corrosion is mostly semantic at this level.

Also the pressure of sharpening can be very high on the actual edge and I wouldn't be surprised if there was some plastic movement there. A relaxing of this could also cause spontaneous dulling.

I have noticed on a couple of knives I don't use but just handle, that repeated touch-ups with a very hard strop last longer and longer each time, until further touch-ups become only very occasional. These blades are also usually coated with oil or wax.

Greg
 
Bill DeShivs said:
Could it be that the stainless is "passivating" itself at the new edge?
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I'm not quite certain what you mean by "passivating" itself.

"Passivation" is usually used as a name for treating the steel with acid to remove any impurities and improve the uniformity of the oxide layer. Obviously, that does not happen on its own. If you are talking about the oxide layer I mentioned in my earlier post, that oxidation takes place almost instantaneously, not over time.

If you are talking about the edge continuing to corrode (oxidize) with time, then we are talking about the same thing. My point is that it is hard to have a perfect oxide matrix extending around the edge, so that at the edge the blade corrodes until not such an acute angle is there.
 
Yes, the oxide layer, or possibly corrosion at microscopic level.
 
it's called atomic migration.the atoms are all sitting in alignment and when the blades are finish ground at the factory,the atoms naturally want to return to where they were before grinding.
 
gpdawg said:
it's called atomic migration.the atoms are all sitting in alignment and when the blades are finish ground at the factory,the atoms naturally want to return to where they were before grinding.
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That's a very good point, its hard to imagine everything is alive and moving.
 
I have noticed some of my knives are sharp like razors every time I check them - definitely no dulling while unused. I have also noticed that some others don't seem as sharp as I remember when I sharpened them and put them away. They are still sharp, just not the same hair popping razor sharp that I sharpened them to. The worst are the crappy steel blades. The best are the VG-10 and the carbon steel blades.

The bad ones are still essentially sharp though and a quick strop seems to get them back to what they should be.

Some that are very good came very sharp when I got them (BK7, BK9, Mora Carbon, AG Russell Ultimate pen knife) but some came not that sharp and I not only sharpened them to a great razor edge, they have stayed scary sharp since. I usually sharpen a knife after I have finished using it and before I put it away - so in theory any knife I grab out of the draw should be VERY sharp. I don't think any of my 1095 or similar high carbon knives have had any problems staying sharp - hell, they even feel VERY sharp after some hard use!
 
The older kids here may remember a lot of talk back in the 70s from the new age folks about placing a new razor blade under a pyramid shaped cover which supposedly allowed it to remain as sharp as a new one for many years. (pryamid power - supposedly bronze knives found in tombs in the pryamids were still amazingly sharp) Scientific tests were actually done to determine if there was any truth to it. The only thing they determined from what I remember was that a sharp edge does indeed get dull from just sitting in air with no use. I would guess it's simply a matter of oxidation acting upon the microscopically thin edge. I have picked up knives that I honed razor sharp months later with no use on them and they did seem to have lost some of their edge.
 
Knives do dull from sitting around exposed to air, due to microcorrosion at the very edge. Both carbon and stainless steels are subject to this, but stainless steels corrode much more slowly. Perhaps the newfangled nitrogen steels like H1 are not subject to microcorrosion, but I have little experience with them.

It's a good idea to oil blades before long-term storage if you will expect to use them afterwards without prior sharpening.
 
DocNightfall said:
Both carbon and stainless steels are subject to this, but stainless steels corrode much more slowly.
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And yet my experience is that my 1095 knives are sharper when I get them out than my stainless steel knives (but VG-10 is better in this regard than the cheaper stainless steels).
 
I find that knives marked 440 are usually 3CR15MoV or some such.

I find it odd that the knife made the trip from the far east set in an importers warehouse then in sellers inventory and the trip to the buyer and arrived hair popping sharp but now will not hold an edge. something more than a burr is at play.
 
Reminds me of the old aviator’s knife the Navy issued in the 60's and 70's. They used to call it the "Butter Knife", no matter how hard you tried it wouldn't hold an edge. My father gave me one about 14 years ago; I'll be damned if it's the only dull knife I own. I have put an edge on it before but it never lasts. The thing looks like a mini K-Bar.
 
I think it's mostly a placebo effect. You expect the knife to be sharper than it is, so it seems dull when you pull it out of storage.

Also I think just about anyone on this forum that tests sharpness uses a method that dulls the knife, however little it is still duller.

Just idle thoughts.
 
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