Should I maintain a carbon steel knife with oil?
I write it as a seasoned carbon steel knife user and a hobbyist knifemaker.

Use edible oil or nothing

Safety first. You can use any oil as long as you are really, really sure you wouldn't mind it added to your food.

Patina is good.

There are two kinds of iron oxide. Let's call them red (rust) and black (patina). Black one is good.


It mitigates red rust
It's less sticky
It's mostly tasteless


It's main drawback - it's ugly.



This is my everyday carbon steel knife. It's scrached and developed patina. It does not mind being used for cooking. It no longer requires wiping every minute, it can well be washed and dried after few hours.

How to develop good patina?

First, the less patina you already have, the slower you need to go. Don't keep virgin steel wet too long. Only after it begins to darken you can allow it to stay wet longer.

Remove red rust when you see it. But don't just use scrubber. If you want to develop patina fast, you should boil your knfe's blade for ten or twenty minutes when you see it getting red. This will convert some red to black. Then gently scrub the rest of red from your blade. If you don't want to boil, just gently remove rust, carefully not destroying patina. 

If you want to artificially develop patina, dijon mustard is especially good for that. Few hours in warm place should do the job. Lemon juice is not half bad, either.