Question about carbon steel

[OSCAR]

A friend of mine said that the darker the patina on a carbon steel blade the sharper edge it will take. I own many carbon steel blades and I don’t think that he is correct. I think it doesn’t effect the edge capability at all. Has there ever been a study done or does anyone know if it’s true or false ? Thanks -Oscar

[cudgee]

.

[Ridgegrass]

cudgee: Now that there's funny !!

OSCAR, I've not heard that but some of those old black ones do sharpen up great. J.O'.

[terryl308]

I dont believe te color as anything to do with sharpening or the ability for the blade to hold an edge. Any carbon steel will turn grey with use. The color it turns has more to do with the chemical makeup of the alloy and what the blade has been used for. Terry

[Mumbleypeg]

I've never heard that before nor have I experienced it personally. I think cudgee has the appropriate response.

Ken

[Colonel26]

As much as I wish it were true, I agree with Cudgee.

I bet what your friend has experienced is an old righteous carbon steel knife with lots of patina and formed that opinion. But correlation does not imply causality.

But this one comes close.......

[cody6268]

Two things that both happen with age as a knife gets older--a dark patina, and as the blade is sharpened a whole heck of a lot, it can get thinner. But, from a chemistry perspective, the patina has nothing to do with it. It's just two things that happen as a knife gets old and used a lot, often in unison.

[kootenay joe]

I have old knives with blades that are black with patina. I think this degree of patina indicates blade came into contact with a substance and was not wiped down. Both blood and potato can really darken a carbon steel blade but not make them take a sharper edge.
kj

[Kase's Kutlery Plus]

I have customers that have that same opinion. They want the darkest blades they can find.

[edge213]

I simply say "nonsense".

[Eustace]

Some time ago I was experimenting with patination with an old knife. Iron trichloride made a dark gray patina, and dilute acetic acid a deep black.
The knife was as soft as yellow cheese.

[Steve Warden]

Some time ago I was experimenting with patination with an old knife. Iron trichloride made a dark gray patina, and dilute acetic acid a deep black.
The knife was as soft as yellow cheese.

[Papa Bones]

I have heard this before. I tend to call it an old Wives-tail. But it may have it's roots to a similar one. Back when I was a teen and learning engine building and hanging around some of the older and more experienced mechanics and "Hot Rodders" of the time, there was a belief that you tried to have a spare engine block as a backup to rebuild. You left it out and let it get rusty then oiled it down and let it sit for several months. I was told (back then) that a rusted block after it was cleaned and rebuilt was stronger than a new block. Now, I have never seen any solid evidence to backup these claims. I am also not a metallurgist so I would not argue with these guys. But many believed this. So maybe, this belief might have kind of bled over into the knife world as far as patina, and blade edge or strength. Some old tales and beliefs are hard to find their origins.

[OSCAR]

I suppose that the only way to know is to add patina artificially to one of two identical knives. I think it’s a wives tale and I don’t want to bother. I can’t see how a bit of oxidation would improve the quality of the edge. I guess I’ll never really know for certain but personally I don’t buy it.

[Mumbleypeg]

I know for certain. It’s not true. Period. Intelligence guided by experience.

Ken

[Modern Slip Joints]

I do not know much for certain but some years ago my young nieces and nephews told me the correct way to patina a carbon knife is to make apple pies with it. I'm pretty sure that you will not find an elementary school kid who will disagree.