Care & maintenance · sources checked 2026-10-23How to care for
a Japanese knife
Short answer: wash the knife by hand with dish soap and a soft sponge right after use, dry the blade and handle with a towel at once, and store it where the edge touches nothing. Never use a dishwasher and never leave it in the sink. That is enough for stainless steels such as VG-10 and SG2. Carbon steels such as Aogami and Shirogami also need wiping during prep and a thin film of oil before storage; the grey-blue colour they take on is a normal patina, not rust.
How much care does your steel need?
The steel decides the routine. Chromium is the element that makes steel stainless: Kai defines stainless knife steel as at least 10.5% chromium, which forms a thin, tightly bonded oxide film on the surface. Here are the 15 steels in our Japanese knife steel chart, grouped by how much care they need:
| Group | Steels | Routine | Why |
|---|---|---|---|
| Carbon steel | Shirogami #1, Shirogami #2, Shirogami #3, Aogami #1, Aogami #2, Aogami Super | Wipe during prep, dry immediately after washing, oil before storing for more than a few days. | 0–0.5% chromium: no stainless protection. Turns grey-blue on acidic food and rusts red if left wet. |
| Tool steels sold as “semi-stainless” | HAP40, SLD (≈ D2 / SKD11) | Treat like carbon steel: dry after each task and never leave wet overnight. | HAP40 has about 4.2% chromium, far below the ~10.5% stainless threshold. SLD has about 12% but is a die steel that makers and shops treat as only semi-stainless. |
| Stainless steel | Ginsan (Silver #3), VG-10, VG-1, SG2 (Super Gold 2), ZDP-189, AUS-8, AUS-10 | Wash and dry after use. No patina forms, but salt, bleach and standing water can still leave rust spots. | 13–20% chromium forms a thin protective oxide film. ZDP-189 needs more care than the rest (see its page). |
Chromium figures are the steelmakers’ published compositions (retailer figures for SG2). Check the cladding too: many carbon-steel knives are a carbon core inside stainless cladding (san-mai), so only the edge can rust, while iron-clad or kurouchi (black forge-finish) blades can rust over the whole face.
1. While you cook
- Keep a dry towel by the board. Kai recommends wiping water off a carbon-steel blade as you go, and Zwilling Japan suggests washing and drying the knife each time you switch ingredients.
- Wipe after acidic or salty food. Kai, Tojiro and Jikko all name salt and acid as the main causes of rust. Citrus, tomatoes, onions, pickles and soy sauce are the usual suspects.
- Scoop food with the spine, not the edge. Tojiro warns that sweeping chopped food across the board with the edge dulls it; turn the knife over and use the spine (mine).
2. After cooking: wash, rinse, dry
- Wash at once with neutral dish soap and a soft sponge. Pinch the sponge from the spine side and move toward the edge, not the other way round (Zwilling Japan). No steel wool or hard scourers: Tojiro and Jikko say they scratch the blade.
- Rinse, then pour hot water over both faces (Kai, Jikko). The heat helps the surface dry faster.
- Dry the blade and the handle completely with a towel or paper towel, then let the knife air-dry in a knife block or stand (Tojiro).
- Never heat-dry. Tojiro says not to dry knives in a microwave or oven, and that holding a blade over a flame can soften the hardened edge.
Two things to avoid: soaking (Tojiro says never to leave a knife in a bowl of water, which can also corrode the handle) and chlorine bleach (Zwilling Japan and Jikko both say it causes rust).
3. Why not the dishwasher?
Kai’s answer is short: only knives labelled dishwasher-safe can go in, and carbon-steel knives and wooden-handled knives are not. The makers give three reasons:
- Rust. Dishwasher detergent and long periods of hot, wet air make knives rust more easily (Tojiro, Jikko). Even stainless steel can spot.
- Chipped edges. The water jets can knock the edge against plates and the basket (Tojiro). A thin, hard Japanese edge tends to chip rather than bend.
- Handles. Jikko notes that heat and detergent can crack and deform resin handles, and that wooden handles swell and split. Most Japanese-style (wa) handles are wood.
4. Patina vs rust: what the colour means
A new Aogami Super or Shirogami #1 blade will not stay mirror-bright. After a few weeks it turns patchy grey, blue or almost black. That is a patina: a thin oxide film formed by contact with food. Dense black iron oxide (magnetite, Fe₃O₄) differs from red rust, which is loose and keeps eating into the steel. A stable patina slows further corrosion, so leave it on.
| Patina (keep) | Red rust (remove) | |
|---|---|---|
| Colour | Grey, blue-grey, purple or near-black; often uneven, following the foods you cut | Red, orange or brown; often in spots |
| Surface | Smooth to the touch, part of the steel surface | Powdery or rough; leaves a stain on a paper towel |
| What it is | A thin, dense iron oxide such as black magnetite (Fe₃O₄) | Hydrated iron oxide that keeps eating into the steel |
| What causes it | Normal use: onions, citrus, tomatoes, raw meat and fish | Water, salt or food residue left on the blade |
| What to do | Nothing. Keep using and drying the knife | Remove it now (see step 4) before it pits the steel |
Should you force a patina? Some cooks soak a new blade in hot vinegar or rub on mustard to darken it quickly. When America’s Test Kitchen tried a vinegar soak, the blade afterwards rusted more easily and had a matte, grippy surface. They recommend simply using the knife and drying it, letting the patina build up on its own. We agree.
5. Removing rust
- Light surface rust: put a little powder cleanser on a soft sponge or a wine cork and rub gently along the flat of the blade (Jikko, Tojiro). A rubber rust eraser (sold in Japan as sabi-keshi) also works.
- Do not press hard and do not use steel wool. Jikko warns that a rust eraser can scratch the surface and fade the pattern of a Damascus (layered) finish; use it gently, or only on the rusty spot.
- Rust on the edge: do not scrub along the edge, since that is how people cut themselves. Tojiro says to sharpen the rust off on a whetstone instead. Check your angle with our sharpening angle calculator.
- Deep or pitted rust may not come out completely (Kai, Jikko). Many Japanese makers and shops offer resharpening and polishing; ask the maker before grinding an expensive blade yourself.
- Finish by washing, drying and, for carbon steel, wiping on a thin film of oil.
Stainless knives can rust too. Kai says chloride ions can cause rust even on stainless knife steel. Tojiro calls one form morai-sabi (“borrowed rust”): tiny metal particles from tap water settle on the blade and start rust spots, which can turn into pinholes if ignored. Remove them early with cleanser.
6. Storing the knife
- Somewhere dry and airy, with the edge touching nothing: a knife block or stand, a magnetic strip, or a wooden sheath (saya) on a completely dry blade. Zwilling Japan warns that knives touching each other get scratched and lose their edge, so loose knives in a drawer are a bad idea.
- Carbon steel, daily use: after drying, Jikko and Tojiro wipe on a thin film of food-safe oil (cooking oil, or the camellia oil widely sold in Japan for blades) and then wipe off the excess. Jikko warns that too much oil can itself cause rust.
- Longer storage: oil the blade, wrap it in newspaper and keep it somewhere dry (Kai, Jikko, Zwilling Japan). The paper absorbs moisture, and Jikko says the ink’s oil helps prevent rust.
- Wash off the oil before you cook (Tojiro).
7. Protecting the edge
Hard Japanese steels hold a thin edge well but chip if misused. Tojiro’s rules for keeping a knife sharp:
- Cutting board: wood or rubber. Avoid glass and marble boards, which crush the edge, and very hard plastic.
- Not for hard things: crab shells, large fish bones and frozen food chip an everyday knife. Use a thick-bladed knife such as a deba, or a dedicated tool.
- Sharpen regularly: Tojiro suggests sharpening about once or twice a month with home use. Serrated knives cannot be resharpened this way.
Single-bevel knives (yanagiba, deba, usuba) are sharpened differently from double-bevel ones. See single-bevel vs double-bevel.
A 30-second routine to print
| When | Stainless (VG-10, SG2, Ginsan…) | Carbon (Aogami, Shirogami…) |
|---|---|---|
| During prep | Nothing special | Wipe after acidic or wet food |
| After use | Hand-wash, dry blade and handle | Hand-wash, hot-water rinse, dry at once |
| Storage | Block, stand, magnet or saya | Same, plus a thin film of oil |
| Weeks unused | Dry place | Oil, wrap in newspaper, dry place |
| Never | Dishwasher · soaking · chlorine bleach · steel wool · heat-drying · glass or stone boards | |
Still choosing? Rust resistance is one of the biggest differences in Blue vs White steel, Aogami Super vs SG2 and VG-10 vs SG2. Compare shapes in the Japanese knife types hub, or read how to buy a Japanese knife from Japan.
Frequently asked questions
- Can I put a Japanese knife in the dishwasher?
- No. Kai says only products labelled dishwasher-safe can go in, and that carbon-steel (hagane) knives and knives with wooden handles are not. Tojiro adds that dishwasher detergent makes knives rust more easily and that the water jets can knock the edge against other dishes and the basket and chip it.
- Is the dark grey or blue colour on my carbon steel knife rust?
- It is oxidation, but not the harmful kind. Carbon steels such as Aogami and Shirogami form a thin grey, blue or black film (patina) when they touch acidic or protein-rich food. Black iron oxide (magnetite) is a dense film that slows further corrosion, unlike red rust, which is loose and keeps spreading. Leave the patina; remove red or orange spots.
- How do I remove rust from a Japanese knife?
- Japanese makers recommend a powder cleanser on a soft sponge or a wine cork, or a rust eraser, rubbed gently on the flat of the blade. Do not use steel wool or hard scourers. Rust on the very edge should be sharpened off on a whetstone rather than scrubbed, because scrubbing an edge can cut you. Deep, pitted rust may not come out completely.
- What oil should I use on a carbon steel knife?
- A food-safe oil applied as a very thin film. Sakai maker Jikko and Kai mention ordinary cooking (salad) oil; camellia oil, widely sold in Japan for blades, also works. Wipe off the excess, because too much oil can itself cause rust, and wash the knife before using it again.
- Do stainless Japanese knives like VG-10 or SG2 rust?
- Rarely, but they can. Kai notes that stainless knife steel can rust from chloride ions, and Tojiro warns that mineral particles in tap water can start small rust spots that turn into pinholes if left. Wash and dry stainless knives after use too, and keep chlorine bleach away from them.
Sources
- Kai: FAQ — why did my knife rust and how should I care for it? (stainless and carbon steel, dishwasher)
- Kai: the appeal of carbon-steel (hagane) knives — daily care, hot-water rinse, stainless definition
- Tojiro: knife care (washing, drying, dishwashers, oil, rust removal, “borrowed rust”)
- Tojiro: keeping the edge sharp for longer (cutting boards, hard foods, scooping with the spine)
- Tojiro: sharpening and care (sharpen once or twice a month, do not soak, no oven or microwave drying)
- Sakai Jikko: everyday knife care (carbon steel routine, oil, long-term storage)
- Sakai Jikko: removing rust from a knife (cleanser, cork, rust eraser, Damascus finishes)
- Sakai Jikko: why knives rust in dishwashers (heat, detergent, handles)
- Zwilling Japan: knife use and care (bleach, wooden handles, storage)
- Kotobank: 錆 (rust) — red rust vs black magnetite
- America’s Test Kitchen: carbon steel knives — why a patina matters (forced-patina test)
The care steps come from Japanese makers’ own care pages (Kai, Tojiro, Sakai Jikko, Zwilling Japan), checked 2026-10-23. America’s Test Kitchen and Kotobank are secondary sources. Found a better source or an error? Tell us.