A petty knife is a small Japanese utility knife, typically with a blade between 120mm and 180mm, designed for precision tasks like peeling, trimming, and slicing fruits and vegetables. You need one when your main chef’s knife feels too large for detail work, think deveining shrimp, cutting garnishes, or any in-hand peeling where a bigger blade gets in the way. Its slightly longer and slimmer profile than a Western paring knife gives you more control for intricate cuts without sacrificing the nimble feel you want for small jobs. If you regularly find yourself reaching for a smaller blade for finishing work, a petty fills that gap cleanly.

A petty is not a replacement for a gyuto or santoku. It lacks the blade length and belly for efficient chopping, rocking, or breaking down larger proteins. If your work is mostly bulk prep, like dicing onions or slicing roasts, a petty will feel slow and underpowered. It also won’t handle heavy tasks like splitting bones or prying, so treat it as a precision tool, not an all-rounder.

The petty’s role in a Japanese kitchen is as the smaller counterpart to the gyuto, built for tasks where a full-size blade is clumsy. At Knives and Stones, the petty category covers a range of steels including VG10, White#2, Swedish Steel, VG5, SG2, and MV, from makers like Sakai Takayuki, Masamoto Sohonten, Ryusen, Nigara, Hatsukokoro, and Sentan. Most are double-beveled, and the blade length runs from 120mm to 180mm, which is what gives it that balance of reach and precision. For more on how this fits into your knife kit, see the Knives and Stones Education Centre.

Yes - carbon steels such as Aogami (Blue) and Shirogami (White) react with food, moisture, and acids. Left wet they can spot or rust, and with normal use they develop a grey-blue patina. That patina is expected and is part of owning a carbon-steel knife; it is not damage.

Care is simple once it becomes habit: hand-wash in warm water, never leave the knife soaking or sitting in a wet sink, and dry it thoroughly the moment you finish. Avoid the dishwasher entirely, and wipe the blade between tasks when you are cutting acidic foods like citrus, tomato, or onion.

If the knife will sit unused for a while, wipe a very thin film of food-safe camellia oil (or a neutral mineral oil) onto the blade before storing it. A light surface rust spot lifts easily with a rust eraser or a little Bar Keepers Friend; sustained neglect is the only thing to really avoid.

Carbon steel rewards this small amount of attention with a keener edge and easier sharpening than most stainless. If you would rather not think about maintenance at all, ask us about stainless or stainless-clad options instead.

Aogami Blue steel, specifically Aogami Super (Blue Super), is a high-carbon Japanese knife steel made by Hitachi that chefs value for its ability to take an extremely sharp edge and hold it longer than most other carbon steels, thanks to a composition with 1.45% carbon, 2.25% tungsten, and added vanadium.

The "Blue" in Aogami refers to the color of the paper the steel is wrapped in at the mill, not the steel itself. Aogami Super is an upgraded version of Blue Steel No. 1, with higher carbon and tungsten content plus vanadium, which refines the grain structure. This lets the steel be hardened to HRC 62–65 without becoming overly brittle, giving you a blade that can be ground very thin for aggressive cutting performance while still resisting chipping in normal use. The trade-off is that, like all high-carbon steels, it is not stainless—it will rust if left wet or acidic, so you need to wipe it down and keep it dry.

Dry it as soon as you finish, keep it somewhere dry, and let a patina build. Do that and aogami (Blue) steel will hardly ever rust.

Aogami #1, #2 and Super all have less than half a percent of chromium, nowhere near what a stainless steel needs, so water left sitting on the blade will spot it.

The routine:

• Wipe the blade as you go, especially after onion, citrus or tomato.
• When you finish, wash it in warm water with a little soap and dry it straight away with a towel. Don't let it air dry or leave it in the sink or the dish rack, and never put it in the dishwasher.
• Store it dry: on a magnetic strip, in a saya or in a block in a dry spot. A damp drawer is the worst place for it.
• If it's going to sit unused for a while, wipe on a thin film of camellia or mineral oil.
• Let a patina form. The grey, blue and brown colours you get from cutting meat and vegetables are a stable oxide layer, and it slows rust down. Orange or red specks are rust.

If you do find rust, lift light orange spots with a rust eraser and a little water, then dry and oil the blade. We stock the CKK and Naniwa rust erasers. Rust on the edge itself comes off the next time you sharpen. Deep pitting is a job for us, so bring the knife in.

On a stainless-clad knife only the thin line of aogami along the edge can rust; the cladding stays clean. A carbon-clad or honyaki blade can rust over its whole face and needs the same care all over.

Yoshimi Kato is known for hand-forged Damascus knives with thin geometry and strong cutting performance, working primarily in SG2 and Aogami Super steels from his workshop in Echizen's Takefu Knife Village. He is a certified traditional craftsman (伝統工芸士, earned 2008) and the third-generation blacksmith at Kato Knife Manufacturing, which was established in 1948. His reputation rests on precise heat treatment of premium steels and distinctive Damascus patterns.

Kato also produces knives for the Masakage brand. In recent years he has drawn inspiration from his friend Yu Kurosaki, another Takefu Knife Village smith, and developed newer designs such as the Hyo line. His new gallery and workshop recently opened next to Kurosaki's gallery in Takefu, reflecting the close creative relationship between the two makers.