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Rust, Oxidation, Patinas, Knife Care? Help Please.

Wed Aug 28, 2013 8:25 pm

So I've had my Richmond Laser AS for about 5 days now; and about two days ago some blue-black spots began to appear near the edge of the knife on both sides [where the stainless steel cladding ends.] This sent me into a bit of a panic and after some 'googlin' I surmised that it was an oxidation that is naturally occurring in carbon steel; Still, I have been wary of any development or worsening in the knifes condition since oxidation is a precursor to rust.

I have been giving my knife a final inspection before bed and in the morning after I wake up, in order to observe any changes. And I was horrified to discover this morning that my knife was in this state, this morning:


However, the condition of the other side of the knife is unchanged from how it was last night after I finished inspecting it.


I have been taking good care of the knife, so why is this even happening? Much less to just one side?

If the task I'm working in a particularly lengthy one, I'll wipe it down throughout the job. Otherwise, at the end of a task I run the knife under warm water and maybe some soap to clean it, then I dry it with a cloth rag or napkin/paper towel, I then run my fingers down by the edge to feel for any residual moisture or food particulates. Is this a bad process? Is the warm water/soap harmful to my knife? I wouldn't think so, considering the wash I give it is as quick and thorough as I can get it. Not to be insulting to Mark Richmond, but is it possible that the knife I got has some sort of defect?

Sad as it sounds, this knife is one of the nicest things I own and I'm upset that despite my best efforts my I'm unable to preserve the integrity of the knife. Am I making some sort of rookie mistake here? Apparently touching the blade is a no-no as well due to your finger oils, maybe it's that? I've been researching ways to clean rust from a knife, some say to use a metal polisher or vinegar but others say that will compromise my knife entirely? I've seen a product called "Bar Keepers Friend" mentioned around these forums a few times. Should I get some of that, is it safe to use on the carbon steel?

Can I sharpen the rust off, I've heard you can? I don't even have the appropriate steel for my knife yet, much less good quality sharpening stones.

Now if I'm able to return my knife to it's original condition, whats the best way to preserve it? I was thinking of introducing some light vegetable or olive oil to my Saya, which will keep the knife lubricated and I'm hoping it will prevent rust? Or will that simply worsen my situation? I'd rather not do that, thanks.

The area I live in is not seriously humid, I keep the knife sheathed regularly but admittedly I did forget to sheath is last night, I left it lying in the box it came it.

I don't mean to sound to panicked, I just really like this knife and it would be a crying shame for it to go to hell after such a short period of ownership. Being out 200 dollars would suck as well. I could really use some advice at this point, please.




Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Wed Aug 28, 2013 8:39 pm

Just looks like patina to me. This happens to carbon steels and with enough use, it'll eventually even out and be uniformly dark. Just watch out for orange. Orange and powdery = rust.

Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Wed Aug 28, 2013 8:40 pm

Don't worry. The integrity of your knife is not being compromised at all. Go ahead and clean it. >>HERE<< is a great how to video by our own Melampus. The spots should be gone when you are done.

I think what is happening is you just missed that one side of your knife was not fully dry when you put it away is all. Always be sure to look at both sides. You will be surprised how easy it is to leave some water on one side of the knife when you pull it through a towel to dry it. Good luck!

Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Wed Aug 28, 2013 8:53 pm

Use food grade mineral oil if you want to keep it coated. I've read that most cooking oil will go rancid over time.

Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Wed Aug 28, 2013 8:54 pm

>>HERE<< Is another video where Chef Nobu shows Martha Stewart how to clean knives. His method works well too. Instead of the daikon you can use the cut side of a potato or cucumber or whatever firm veggie you might have an end of.

Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Wed Aug 28, 2013 10:56 pm

The dark blue/purple color is the patina from the carbon core reacting to the foods that have been cut. It's normal for carbon and will generally "settle down" as the steel reacts fully and there isn't steel left to react except at the edge bevel itself when it's resharpened. Patina is the steel reacting to the metal and oxidizing as you say, but it is not a precursor to rusting. The steel reacts and then will generally stop reacting and the surface will be protected. It's a controlled oxidizing, much like gun bluing or parkerizing; the metal reacts on the surface until it's fully reacted and then pretty much stops. Patina's do not go to rust unless moisture is left on the blade. With the one side rusted and the other not, it looks like there was moisture left on the blade. Cloth towels especially are notorious for this, but it can happen with paper towels, too since they can redeposit moisture on the blade. I leave any freshly washed/dried knives out for at least 30 min and then recheck and rewipe if needed with a fresh paper towel to make sure all moisture is off of the blade before putting in a sheath/saya/block. Sometimes the patina doesn't really appear for a few days or gets much darker after the blade is washed/dried. I really like the blues and purples AS steel gets. You can also force etch it in vinegar or ferric chloride to give it a dark black look, but the patina may still form over the etching.

BKF (Bar keepers Friend) will remove oxidization from the blade quickly and easily, just fully rinse and wash it off when it's done. But the carbon will keep reacting after each time the patina is removed. I wouldn't sharpen the rust off; it should come off with BKF, Scotchbrite pade, 0000 steel wool/oil, etc or one of the other methods listed above. Just remember that many of these methods are slightly abrasive and may dull the edge a bit if done aggressively enough.

I wouldn't oil the inside of the saya itself; you can put some oil on the blade and wipe it around, but if it's dry, you shouldn't need to unless you aren't going to use it for a long time. I use mostly carbon knives and wash and dry with paper towels, let sit out and then recheck a little later to make sure there is no moisture on the blade. No rust on any of my carbons, just the patina/etching!

Looking at the pic with the rust, do you see how there is a line of rust drops mostly down the blade in a line? If moisture is left on a blade when drying, it will often be in a line like that, with other areas here and there. I would say that there was a tiny bit of moisture left on the blade and that it what caused it to rust. That looks only like surface rust, so it should come off with the veggie trick for you. It doesn't look like the rust has pitted the steel.

Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Thu Aug 29, 2013 7:34 am

MERL <> That knife was left wet overnight. You're driving yourself so crazy babying a tool, you missed the most basic of care. A little BKF will take that out in an instant although naked steel wool will, too.

Relax. It's a tool... not jewelry.

Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Thu Aug 29, 2013 8:34 am

+1 on Bar Keeper's Friend. Also, you will get a patina on the knife and you should encourage it. The patina will form a thin barrier between the steel and the stuff you're cutting and will lessen the reactivate of the edge. It looks cool too.

Sue always lets knives drip dry so I make a habit of going into the kitchen before I go to sleep and checking. If there are some water spots or small rust spots I can usually just wipe the rust off with a quick wipe of a sponge and a dry towel.

Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Thu Aug 29, 2013 10:36 am

Patinas make life much easier so I would encourage it to develop like others have said.

If you don't like it. Bkf followed by rubbing a little mineral oil spead over the exposed carbon steel. The oil will keep oxygen from reacting with the steel and to limited extent cover residual water residue preventing rust from that as well.

Re: Rust, Oxidation, Patinas, Knife Care? Help Please.

Thu Aug 29, 2013 10:46 am

If you want to minimize an uneven patina, and make knife care easier, force one. With a stainless clad, try an onion, mustard is harder to control and can get really dark in spots. First, remove the spots on the edge with BF and rinse well. After it dries, get an onion and draw the blade through it a few times till the edge is nice and wet. Then just let it sit and dry for 30-60 minutes. Repeat if you think it needs it. This should give you a nice blue/grey patina as a base. Then, as you use your knife, it will add to the patina. Also, by starting the patina, you'll have a bit more time until you need to wipe your blade down when prepping.
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