Kitchen knives & cutting boards - Pro-Idee Cuisine

The blade material

Blades mostly consist of metal – nowadays almost always of knife steel – with some exceptions such as ceramic, titanium alloys or dendritic cobalt alloys such as Talonite® or Stellite®. In even rarer cases, plastics are used but these hold their edge comparatively poorly.

Knife steel

Raw steel has a very wide range of properties that can be aligned precisely for a certain purpose namely composition, production and heat treatment. For this reason, knife steel contains, apart from iron, primary elements such as carbon, chromium, molybdenum and vanadium. For quite some time now steel for kitchen knives has been alloyed with molybdenum to make it tolerant to dishwasher cleaning.

The better the knife holds an edge, the longer it takes until the blade needs to be sharpened again. The ability of a blade to hold an edge and to stay free from rust is determined by the composition of the steel used. The ability to hold an edge depends largely on the amount of carbon added to the steel. Rust resistance can only be achieved if the steel contains a minimum of 13 % chromium.

Rust resistance and edge holding ability largely exclude each other. Adding chromium parts to steel means the development of large carbides which quickly lead to tiny chinks in the edge of the blade and that quickly makes the knife blunt.

Good knife steels commonly used are for example:

• X50CrMoV15:
  A martensitic stainless steel, that is used a lot for low-priced Solinger knives – like our knife collection Böker Forge.
• Cronidur:
  A very hard and wear-resistant steel that is used for example at Zwilling for their fine knife series.
• 420:
  These high-alloy steels stand out for their good corrosion resistance, breaking strength and low price. However, they are not particularly hard, and although this has a detrimental effect on their ability to hold an edge, it also facilitates re-sharpening. A variant that holds an edge better is 420HC steel, which is often used for Buck knives. A higher amount of carbon results in a better ability to hold an edge.
• 440C:
  This steel is especially corrosion-resistant due to its high amount of chromium and can hold an edge well due to its high amount of carbon. It is used for example by Böker for its Saga series.
• D2:
  D2 is a rust resistant, American tool steel which contains 12% chromium. It distinguishes itself with excellent hardness and ability to hold an edge, paired with good breaking strength.
• VG-5 / VG-10 / VG-12:
  Very hard, stainless steel, used in many Japanese knife series as core steel.
• AUS-4 / AUS-6 / AUS-8 und AUS-10:
  These Japanese steels are widespread and their properties are comparable with 440 steels. Although they have a slightly lower hardness, they are sharpened more easily and are stainless as well.
• Carbon steel (1050 – 1095):
  A collective term for non-stainless steel with a high carbon content. This steel has outstanding cutting properties and can be sharpened very easily, though it is not stainless.
• Aogami / Shirogami:
  Equally non-stainless carbon steels from Japan
• SG-2:
  A powder metallurgy, manufactured stainless steel that is very pure and can therefore be extremely hardened.
• 12C27:
  12C27 steel is also known under the designation Sandvic 12C27 or Swedish steel and is used by many knife manufacturers, for example by Scandinavian makers such as EKA or for Laguiole knives. Depending on the hardening process, this commendable steel shows varying properties with regard to hardness, ability to hold an edge and ease of sharpening.

Hardness of knives is given in HRC – hardness according to the Rockwell scale. Normally, blades have a hardness between 52 and 64, and sometimes above higher.

Ceramic

High-end ceramics based on aluminium and zirconium oxides have some advantages over steel. They are stainless, dishwasher safe, extremely wear-resistant and up to ten times harder than steel. The blade remains sharp for a long time. Furthermore, ceramic is very lightweight, although this is sometimes seen as a negative property. Known manufacturers are, for example, Echtwerk, Gräwe and Kyocera.

Due to their extreme hardness, ceramic blades are substantially more delicate than steel blades. If a ceramic blade becomes jammed while cutting cauliflower, broccoli or cabbage, it will easily break. Also, if dropped, a ceramic knife will often break.

Ceramic knives also lose their sharpness with time. A diamond wheel is normally used to re-sharpen a ceramic blade: Conventional grinding sharpeners cannot be used.

Ceramic knives are the first choice for allergy sufferers. For example, a chromium / nickel allergy is relatively common. Ceramic is an absolutely neutral material and one that does not give off any substances. In addition, it can be cleaned in the dishwasher at high temperatures. This way, germs or deposits of allergenic foods can be safely removed.

Structure of the blade

The goal is a strong blade that can be finely milled. If too hard, a blade breaks – and if too soft it cannot be sharpened properly. Mono steels reach their limits quickly here. Blades of good quality therefore consist of multiple steel layers with different properties.

• Mono steel blade:
  This blade consists of only one layer of steel (which should not be too hard in order to prevent breaking).
• Three-layered blade:
  A core made from very hard material is enclosed by two layers of softer material. The core can be milled very finely due to its hardness. The outer layers protect the core from breaking. Japanese blades are often structured this way.
• Damascus blade:
  Similar in structure to the three-layered blade. The difference is that the flanks are protected by multi-layered Damascus steel. The effect is approximately the same, but it looks much better – see for yourself: Shun Premier Knife “Tim Mälzer” 
• Wild Damascus:
  Damascus steel is manufactured by alternately forging layers of high-carbon, hard steel with low-carbon, soft steel on top of one another. Subsequently, the material is folded, quickly resulting in several hundred layers. The many forged layers lead to a steel that, despite its high degree of hardness, remains flexible and break-proof and that stands out with its particular look. – see for yourself: Nesmuk Cooking Knife C90. Such solidly forged, core-free Damascus steels are rather exceptional nowadays. Nowadays they are only manufactured by hand by extremely well trained blacksmiths. Prices are accordingly.

Handle material

Cooking knives with ergonomic handles feel particularly secure in the hand. They adapt perfectly to the shape of your hand, so you shift it less when cutting. Handles with an ending are useful. Here you feel the transition to the blade and at the same time, you have a secure rest for the index finger, which often moves toward the blade. A knife handle made from wood should be polished, so that it withstands food acids. The wood you choose does not make any difference to the functionality of the knife. Stainless steel is especially easy to clean, plastic handles can rub a little and so lead to blisters on the hands during kitchen work. Cheap cooking knives often have a plastic handle, so pay attention to well-finished transitions when buying a knife.

Manual labour

Manual labour has its price. Normally, the more production stages carried out by machine, the cheaper a kitchen knife will be. Some Damascus steel knives laboriously made by hand over months can easily reach the price equivalent to the value of a small car. However, with good care, such a knife will last a lifetime.

Craftsmanship

One can, by all means, manufacture very different knives from the same source materials. The higher the effort invested during processing, the more expensive a knife will be.

Simple quality: Stamped blades

For kitchen knives of low quality, the blade blank is stamped out of a sheet and whetted mechanically but only at the edge.

Good quality: Stamped blade, thinly ground

The blade blank is stamped out of a sheet and is ground all-over from back to edge. This results in a fluent transition between the side and cutting surface of the blade, which makes cutting considerably easier. At the same time, the pores of the metal close. This reduces the resistance when sliding through objects, and improves protection against acid and rust.

Premium Quality: Forged blade, sharpened by hand

The blade blank is formed freely or forged – possibly as a Damascus blade – in a die. This requires a lot of understanding and experience from the cutler. The forging compresses the material, and the structure becomes more uniform. The blade obtains its eventual form of a flattened wedge with a thinly ground, stamped blade. Forged blades are normally sharpened by hand.

Sharpening and honing

Nowadays, knives are predominantly sharpened mechanically. Traditional sharpening by hand is only used for particularly premium knives. Depending on the type of blade, sharpening by hand can consist of more than a hundred working steps.