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Cleaning Damascus Chef's Knives


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I've made several Damascus [1084 /15n20] chef's knives for Holiday gifts.....I gave one away as a trial and the recipient says she won't use it because the "black" keeps coming off no matter how many times she washes it....Any solutions, these already have handles on them.

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Hi Geoff...Happy Thanksgiving

 

The black is just the usual result from making Damascus...Since I usually make "Sporting knives" nobody has ever cared,,,Since she's cooking a thanksgiving dinner, She washed the knife then dried it with paper towels and black appeared on the towel after several washings...I just cleaned the blade for her its alcohol and that seemed to work, but others must face this problem too...I just wonder what other makers do.

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What do you etch in and how do you finish it? For myself I etch in a very dilute ferric chloride until topography shows up. I then spray down with ammonia, and without wiping it off, use a hairdryer to dry the whole knife (this "sets" the oxides) Some folks boil the blade in water after etching to set the oxides. I then lightly brighten up the highs with 2000g sandpaper and once that's done, buff lightly with a fine rouge.

Edited by Austin_Lyles
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So the black is scale, iron oxide. Not harmful, but maybe unsightly. You can etch and then buff the steel, but you get a lot less contrast on the steel. You could do a boiled rust surface, I think Wes Detrick has a tutorial here somewhere. I don't think I'd cold blue a kitchen knife, but the hot blue is pretty permanent, I don't know for sure. You could do an oxide surface, but that might interfere with your temper.

 

I think a flash rust and a light polish to hit the high spots is the way I'd go.

 

Geoff

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I wouldn't suggest the rust bluing for pattern welded knives though. I think you wouldn't be able to see any pattern after it. But, just for kicks, I talk about it here in one of my knife posts.

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you can darken in instant coffee.I etch for topography, then scrub all the oxides off with baking soda. once the blade is clean I soak in the coffee fore a hour or two, (large costco sized container to about a gallon of water and skim off the oils)

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It's inevitable. However, as Brian said, oiling is the key. Oil after and sometimes before and it shouldn't be a problem. Higher layer blades seem to have less of a problem, as far as I've seen with mine. Oiling with vegetable oil (canola for you guys I think) is obviously food grade and works fine.

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I like the coffee soak, but what it's probably doing is creating ferric tannate. Coffee contains tannic acid and other acids that are good at both oxidizing and converting oxides into more stable compounds. Ferric tannate is a good passivating layer, and is very stable in the right conditions, but it does rub off and stain other object black/purple. It was used as black/purple ink for a long time since its discovery.

I don't like leaving oxides on etched blades. I scrub them off with baking soda and let the etch show the pattern as texture rather than dark/light contrast. There is still some contrast, but not in the form of a porous oxide layer.

Oxides can be passivated by converting to stable compounds, but most of these are porous and need some other kind of protection from the elements. Boiling rust creates more stable, less porous magnetite (Fe3O4) which is IMO the most desirable state if you're going to leave oxides on the steel. Since your etching will raise the nickel bearing layers and relieve the lower alloy areas which you want to blacken, card or rub the surface to remove oxides from the nickel bearing steel and then boil. The contrast will be much better than leaving oxides that are unstable and attempting to fix them with wax or oil.

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