Blemishes on a new carbon steel knife

Black Sheep

My girlfriend bought a pair of carbon steel knives while she was in Japan recently. They're Aritsugu kitchen knives, but it seems like this is the most likely forum to get an answer on a small problem we're having.

After the first time she used them (cutting a chicken and some vegetables - light work) she washed the blades clean with hot water and some dishwashing liquid, wiped them and put them aside to air-dry as per Aritsugu's instructions.

Small blemishes have appeared along the edge, little pools of discolouration like rust spots.

I have attempted to scour them off, first with a cloth and hot water, then last night with a Sentry Solutions cloth and a little bit of WD-40 to try and loosen it.

Whatever it is doesn't seem to be shifting and it almost looks more like discolouration of the steel rather than something that is lying upon it.

If it were a cheaper knife or a field knife I would try and scour it with something more abrasive but Artisugu advise against using steel wool or similar.

So, two question-

(1) What's it likely to be? (I thought maybe there was some powder left on the blade when it was sold from when it was made, or from the final sharpening, which has oxidised or something)
(2) What do I do, whilst bearing in mind these are some really nice knives I don't want to abuse?

Tackleberrywho

there is a guy on this Forum Deise Mise, PM him. he is an expert on blades but not always on the hunting forum.

Do a search in the boards.ie search box for "Deise Mise" and you should find him

Hibrion

I'm no expert, but, carbon steel blades need to be oiled more often than more stain resistant steels. Because of this they really aren't ideal for kitchen knives.
A light coat of a food friendly oil on the blade before putting it away will stop these blemishes appearing. The spots on it at the moment will come out with a good clean and some elbow grease.

Deise Musashi

Carbon steel blades generally develop a patina, it's a surface oxidation that protects the blade and prevents rust. Some pics would help, but it's unlikely to be rust already. Possibly some dust from grinding was on the blades, but Japanese grind on wet stones and wash away all swarf.

Is it a Japanese or Western style blade? Single chisel ground or symmetrical bevel?
Did your knives come sharpened? Often this maker ships knives with only an initial bevel on it.

Another, rather unpleasant surprise, if you didn't know about it upfront, is that Aritsugu knives, unless special ordered, come pretty much dull. I already knew about that, based on my first experience with Aritsugu Honkasumi yanagiba. That practice of not putting the edge bevels on the knife is also nothing Aritsugu specific. Many Japanese makers do that, and there is a special term for putting initial edge on the knife like that - Honba-Tsuke. Apparently the reason is that, if you are buying that kind of knife, you know what you are doing, and you, or your favorite sharpening guy, will put the best edge that suits you and your use.

Washing by hand in very hot water and drying straight away then storing are good practice for Japanese blades. Rust on the edge can be polished off with fine wet and dry paper, waterstones or a fine abrasive like autosol or brasso. Wash well and dry straight away.

This video is from the makers.

https://www.youtube.com/watch?v=mqpMSdC3zLs

These are very nice knives by some of Japan's oldest makers, keep them out of the dishwasher and they'll last forever.

carbon steel blades need to be oiled more often than more stain resistant steels. Because of this they really aren't ideal for kitchen knives.

White mineral oil is best, light coat and wipe off. Can be had in any pharmacy or in Ikea as cutting board oil. Camelia oil is traditional for Katana if you prefer...

Carbon steels take such a nice fine edge though, especially white and blue paper steels in high hardness 3mm thick blades from Japan's best makers! Murray Carter, Watanabe, Hattori, Maestro Wu all offer carbon steel blades, it's good stuff but needs a little more care.

If you ever need them sharpened drop me a PM, I've some new 3000, 5000 and 10000 grit Chosera stones, and glass polishing blanks for my Edge Pro that need some decent steel to show off what they can do


Just noticed OP's name, Ruairi is that you? I'll be coming up to see Mick if you want me to bring the edge pro with me.

Hope this helps, any other questions feel free to shout.

And this thread is useless without pics.!

Tackleberrywho

I knew you'd be the man with the answers!

davymoore

I'll second what Deise says about the Patina, High carbon steels are prone to take on a patina especially when used on acidic materials such as Tomatoes, onions lemons limes etc. The Patina generally appears like a dark grey staining on the blade. It is doing no harm but can look unsightly. But a lot of folks buy knives from high carbon steel because they actually want that look to their knives.

Davy

Black Sheep

Thanks Eric-

These were sharpened in the Aritsugu shop for us, so they're good to go. Scary sharp.

Upon closer inspection (and a little more research) I think you're right that it's probably a patina versus anything to be overtly worried about. It hasn't developed any further after more use.

Cheers, and see you at the seminar.

Deise Musashi

No bother, if ever they need touching up just let me know

See you in November :eek: