Photo by Molly DeCoudreaux
Always use knives for their intended purpose unless you just have amazing knife skills and can pull it off. Generally if you think you shouldn’t do something with your knife don’t. Coconuts and the center of bones will win a fight with your Japanese knife most likely, don’t do it.
Carbon steels are a variety of steels with a chromium content less than 13%, the reactivity or rate at which carbon steels will oxidize will vary greatly but care must be taken to avoid rust. Water is the primary agent of rust but foods that have a very acidic or basic chemistry or are high in salt will have an extra reactivity during cutting. Wipe the blade dry during heavy use and after washing (soap is OK, avoid using the abrasive side of sponge if possible) but always avoid soaking and out of dishwashers.
Carbon steel will form a patina with careful use, this is a light layer of oxidization which forms before rusting, some prefer to remove it often others like to cultivate it, it’s up to you. If orange rust forms remove it with the finest abrasive possible (coarse abrasives will invite further rust by providing places for water to sit, we like to use the mud that forms from fine Japanese finishing stones on a rag to polish off light rust, silver polish pastes with silica will function in the same way. For deeper heavier rust, use stronger abrasives, a fine sandpaper or scouring powder can be helpful.
Stainless steels are a variety of alloys with over 13% chromium content, stainless steels vary greatly in their stain resistance but all can rust under the right conditions. Generally, higher quality cutlery stainless steels have a higher carbon and lower chromium content and are less stainless than alloys developed for heavy rust resistance (such as marine environments) and can corrode if soaked or put in a dishwasher. There is no such thing as a ‘dishwasher safe’ knife there are only knives that get destroyed slower in the harsh conditions inside a dishwasher.
For stainless or carbon steel knives we recommend using either end grain hardwood or length grain soft wood cutting boards, for extremely hard high carbon steels dense softwood can be a better choice than hardwood as it is easier on the edges. Length grain bamboo is especially harsh on edges as are many plastic boards, there is no such thing as a glass cutting board (they are a square plate that hates your knives).