Determining if Carbon or Stainless

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kenk

Joined
Oct 5, 2004
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Aside from letting it rust, is there a relatively easy way to determine if a blade is carbon or stainless?

I have a Mora knife purchased long ago from a small sporting goods store and haven't a clue wether the blade is carbon or stainless. It hasn't received much use to date and is still quite shiney.
 
If it looks just the same as when you bought it, it is probably stainless. If it is carbon steel it will tend to develop a bit of a dull grey finish, even if you took pretty good care of it. You could touch just the edge with a little lemon juice and leave it overnight. If it is carbon steel it will rust. You can remove the rust by sharpening that area.
 
I think that stainless isn't normally magnetic. Having said that, there are some ways to make a stainless knife magnetic.

If a magnet doesn't stick, its more likely to be stainless.
 
jmknife said:
If a magnet doesn't stick, its more likely to be stainless.
Click to expand...

I just tried this. Magnets will stick to S30V, 440C, ZDP189/420J2, AUS8, and 420HC. All of the stainless steels I tested in other words.


Maybe if kenk posts an image of the knife, it can be identified and we can let him know for sure. The other option would be to stick the knife in an apple and see if it stains.
 
Knife blade stainless sticks to magnets, stainless steel sinks and bowls don't stick to magnets.
 
All the stainless steels used for knives are magnetic. (If you really want to be pedantic, nonmagnetic steels were tried, early in the 20th century -- didn't work very well, but a few of those old knives are still around....)

When I was a boy I bought a ribtickler that I thought was stainless. It didn't say stainless or rostfrei or inox on it; I just assumed it was stainless because the blade was so shiny. Then I cut a lemon in half with it, and was amazed to see a dark patina develop instantly, before my very eyes! :eek:
 
Slice a lemon and don't wipe it off (or apply a drop of vinegar). Carbon steel will corrode pretty quickly. The SS used in Moras is very corrosion resistant and should show no change.

I have used one of the cheap red-handled Moras as a kitchen knife for years, and it's still as shiney as new, save for some small scratches.
 
For three bucks and some change you can buy a gun blue solution at Wal Mart called Perma blue. Apply a cotton tip applicator soaked in it to the spine of the blade. Let it set in one spot for about five or ten seconds. If it turns color it is non stainless. If it is unaffected it is stainless.

This selenium dioxide solution is also known for immediately dulling a non stainless edge. So don't let it drip on the edge unless you want to know in a way that will require resharpening after it is soaked because if it is a high carbon steel it will be dull as can be immediately upon contact with the liguid.
 
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