• Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Blade
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Integral
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Profile
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Choil
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Integral
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Handle
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Handle
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Profile
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Handle
  • Isasmedjan Gyuto 240mm Full Kasumi Integral Birchbark & Brass - Choil
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Gyuto 240mm Full Kasumi Integral Birchbark & Brass

Gyuto 240mm Full Kasumi Integral Birchbark & Brass

By Isasmedjan

No longer available

Jonas Johnsson

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Some bladesmiths emphasise a focus on technical details, some are all about clean lines, others like to focus on technical geometry. While Jonas is certainly always focussed on performance, his work is all about heart and soul. Consider this, the knife featured here has taken approximately a year to produce. Starting in spring 2021 Jonas would have walked out into the local forests surrounding his forge and harvested the Birchbark used in the handle of this knife. He had to store and dry the bark over the summer and artfully select each layer of the handle you see pictured here.

However, that’s only the beginning for a knife like this. Forged San Mai, the steel used for this blade has been pressed together, a sandwich of wrought iron and premium German tool steel forged welded together and then beaten, steel on steel, heat by heat, into the rough shape of a blade. The integral bolster willed into shape with the strike of the hammer. Grinding refines the overall shape of the blade before hours of work on whetstones polishing to produce the Kasumi (mist) finish. That’s a lot of love!

An Isasmedjan knife will grow on you. Rustic certainly doesn’t mean rough, fit and finish is superb. Rather than using the word rustic to describe these knives it would be better to say that they are full of character, charming, with endearing style and class.

As described, this knife features a full Kasumi polish, wrought iron cladding and a very tough, HRC 64+, 1.2419.05 steel core. The handle is a hand harvested birchbark, Rokaku Hanmaru, forged integral with a wrought iron endplate and brass pin.

The profile is Jonas’s classic santoku tipped Gyuto with a decent flat section that gradually settles into a curve towards the tip. The santoku tip gives the knife rigidity, this is not a flexible blade. Stable, satisfyingly weighted, and well balanced. We are not talking workhorse grind though, the knife features a thin, sub 2mm average blade thickness.

Overall, a pleasure to work with on the cutting board.

Between the beautiful birchbark handle and forged integral bolster, the satiny smooth kasumi polish and the artfully crafted performance profile and grind it’s hard to describe this piece as anything short of functional art.

Product Specification
  • Blade Type:
  • Edge Length: 240mm
  • Spine Heel: 2.95mm
  • Spine Mid: 1.98mm
  • Spine Tip (20mm before): 1.2mm
  • Blade Height: 52mm
  • Weight: 234g
  • Cutting Edge Steel:
  • Steel class: Carbon
  • HRC: 64+
  • Blade Construction:
  • Blade Finish: Matte Polish
  • Grind:
  • Handle Construction:
  • Handle Materials: Hand Harvested Birchbark, Wrought Iron and Brass
  • Handedness: Ambidextrous

Blade type

Gyuto

牛刀

The Japanese take on the Western chef's knife, and the most versatile blade in a modern kitchen. A gyuto carries a long, gently curved edge — most often 210 to 270 mm — that allows both push cuts and a rocking motion, with a pointed tip for fine work and enough height at the heel to keep knuckles clear of the board. It handles proteins, vegetables, and herbs without complaint, which is why most cooks reach for it first.

Compared with a European chef's knife, the gyuto is usually thinner, harder, and lighter, ground to a finer edge that rewards good board technique and regular honing. That same thinness is the trade-off: the edge is less forgiving of bone, frozen food, and twisting cuts, and it asks for a little more care in maintenance in exchange for its keenness.

View full knife type guide →

Cutting edge steel

1.2419.05

Low-alloy tungsten-chromium oil-hardening tool steel (variant of 1.2419)

Typical HRC
60–63
Corrosion class
Carbon
Production
Conventional
Origin
Germany

1.2419.05 is the leaner, oil-hardening sub-variant of 1.2419, with somewhat reduced carbon and tungsten — closer to a 95WCr5 in spirit. The "0.05" designation signals an oil-quench specification rather than a wholly separate alloy.

For kitchen knife purposes, 1.2419.05 sits between the simple carbons and full 1.2419 in performance: a slightly easier heat treat, slightly less edge retention, similar feel at the stone. It is a sensible "step up from W2" steel for a smith who values forgiving heat treatment and a cook who values an honest, no-drama carbon edge. Toughness is good; patina behaviour is conventional.

It is uncommon enough in finished knives that you will rarely see it called out by name; when you do, treat it as a near-relative of full 1.2419 with marginally different working characteristics. Among the makers Modern Cooking carries, Martin Huber and Adonis Forged Arts work in 1.2419.05.

View full steel guide →

Blade construction

Laminated Steel

A category covering knives built from multiple layers of different steels forge-welded together. The hard cutting steel is sandwiched between softer outer layers (cladding) that protect the core, add toughness, and often contribute visual contrast.

The most common laminated constructions in the Modern Cooking catalogue are:

SanMai (三枚) — three layers: hard cutting steel in the centre, softer cladding on both sides. The traditional and most common form.

GoMai (五枚) — five layers: a hard core, two intermediate layers, and two outer layers. Adds visual depth and structural complexity.

KuMai (九枚) — nine layers: similar logic, with more cladding layers for additional pattern and structural variation.

GoMai and KuMai are often chosen not only for the additional layers and visual depth, but also because the intermediate layers can act as a nickel diffusion barrier — limiting carbon migration out of the core into the cladding during forge welding, and protecting the core's intended carbon content through the heat of the forging process.

In all cases the cutting performance is determined by the core steel; the outer layers are cosmetic and structural. The lamination contributes corrosion protection (when a stainless jacket clads a carbon core), reduced reactivity, and the visible boundary between core and cladding that gives the knife its character.

View full construction guide →

Grind

Convex

A grind whose bevel bulges outward in a gentle curve from spine to edge, rather than running flat. That extra steel directly behind the edge makes a convex grind notably strong and resistant to chipping, while the curved geometry helps food release and lets the blade glide through dense ingredients with less wedging than a flat grind.

The strength comes at the cost of ultimate thinness and ease of maintenance. A convex edge has more metal behind it, so it is not quite as effortlessly keen as a thinly flat-ground edge, and it is harder to sharpen freehand — holding the curve takes a stropping technique or a deliberate hand rather than a single fixed angle. The reward is an exceptionally tough, smooth-cutting edge.

View full grind guide →

Handle construction

Hidden Tang

A construction in which the tang runs into the handle but stays concealed inside it, rather than showing between two scales. A narrower tang — a full-length stick or a shorter projection — is set into a drilled or burned channel in a one-piece handle and secured with adhesive, a friction fit, or a threaded fitting drawn up against the blade. This is the traditional construction of Japanese wa-handles and many European hidden-tang knives.

The design puts the handle material in charge of the look and feel: a single piece of wood, horn, or composite — often with a ferrule or spacers at the front — is shaped into any cross-section the maker wants, from the classic octagonal and D-shaped wa profiles to fully rounded Western forms. With no steel showing along the grip, the handle can be slim and light, and is frequently made to be removed and replaced, with the balance sitting toward the blade.

View full construction guide →

Shipping & Returns

Shipping

We process orders 5 days a week (Monday - Friday) and ship from our shop in Sydney, Australia. We ship with FedEx, UPS and DHL.

We are happy to offer free international shipping on a variety of orders depending on location and order value.

Free Shipping Regions and Minimum Order Values

For Australia and New Zealand the minimum is $500AUD. For the rest of the world it is approximately €1000EUR. The discount is applied automatically when you reach the minimum cart value at checkout.

Returns

If you're not entirely happy with your purchase, you can return it within 14 days of delivery for a refund. The item must be in its original condition with all original packaging.

  • Returns are accepted for 14 days
  • The customer is responsible for return shipping costs
  • A 15% restocking fee may be applied to change-of-mind returns
  • We do not accept returns on second-hand items for change of mind

Faulty or Damaged Items

You must notify us within 5 business days of receiving your order. Photographic evidence of damage is required. Once approved, Modern Cooking will cover return shipping costs.

Product Care

Cleaning: Clean by hand with warm water. Avoid wetting the handle when possible.

Sharpening: We advise using whetstones to sharpen your knives and a honing rod or steel to maintain the burr between sharpening sessions.

Reactive Steels: Reactive steels like Aogami Super, Apex Ultra or premium reactive German and Swedish steels are susceptible to rust if not properly cared for. Keep the knife dry between uses and when storing for longer periods, wiping the blade with Tsubaki oil or another food-safe oil is a wise choice. A patina can be a beautiful personal feature on your knife and helps to stop rust forming.

Handle Care: For non-stabilised wooden handles, apply Tsubaki oil or another food-safe oil from time to time. Food-safe wax can be applied to both stabilised and non-stabilised wooden handles. Never apply hot wax or oil as you risk warping or damaging the handle.

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