I happen to prefer carbon steel knives. But, as with all carbon steel knives, they require some additional care when it comes to cutting certain foods, such as onions, acidic fruits, etc.
I'm generally very diligent about wiping my knives as soon as I use them; I almost always wipe them down immediately after use and/or wash them off immediately after use.
Yesterday, I was cutting a certain vegetable, wiped off my knives and washed them immediately after use. However, I neglected to completely wipe down my board. I left my knife on the board, and within minutes, I had stains on my knife.
The culprit: water spinach aka Ong Choy.
In your experience, what items stain carbon steel knives the fastest?