How do I stop my Japanese knife from rusting?

Hand-wash and dry the blade immediately after use, never leave it wet or soaking, and wipe carbon-steel blades with a thin film of food-safe mineral oil between uses. A grey patina on carbon steel is normal and protective; active orange rust is the thing you are preventing.

How do I remove rust or stains from a carbon-steel knife?

Light surface rust and stains lift with a polishing paste — we stock Koyo Sunlite Polishing Paste (Blue for Steel) for exactly this. Work it gently along the blade, then wash, dry and re-oil. A stable grey patina, by contrast, is best left alone rather than polished away.

Rust, Patina & Knife Care

Q: How do I prevent rust and care for a carbon steel knife?

Dry the blade immediately after washing, wipe it during acidic prep, and store it lightly oiled. A grey patina is normal; active orange rust is not.

How to prevent rust, why a patina is normal on carbon steel, and the mineral oil and polishing paste we stock for routine care.

Watch

From the Knives and Stones workshop

Our own sharpening and care tutorials — tap to play.

DIY Board Wax (Butter) with Beeswax, Mineral Oil and Coconut Oil

HOW TO USE: Koyo Sunlite Polishing Paste (Blue for Steel)

Questions about this

How do I prevent rust and care for a carbon steel knife?

Carbon steel reacts with water, acids, and food, so the single most important habit is drying the blade thoroughly the moment you finish washing it, and wiping it between tasks when cutting citrus, tomato, or onion. Never leave it soaking or in a wet sink.

A grey-blue patina that builds with use is normal and even protective; active orange rust is what to prevent. If a knife will sit unused, wipe on a very thin film of food-safe oil before storing it.

Our K&S take, naming only what we stock: use the medical-grade Kitchen Knife / Cutting Board Mineral Oil for routine blade protection, and lift light surface rust or refresh a finish with Koyo Sunlite Polishing Paste (Blue for Steel). We do not stock camellia or Tsubaki oil, so we recommend the mineral oil in its place.

Reviewed by James Zhang · Last updated 3 June 2026

We trust this information is correct at the time of writing, but it is not an official document and details may change without notice. If you spot an error, tell us and we'll fix it.

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