knives set with Leather
A kitchen knife is any knife that is intended to be used in food preparation. While much of this work can be accomplished with a few general-purpose knives – notably a large chef’s knife, a tough cleaver, a small paring knife and some sort of serrated blade (such as a bread knife or serrated utility knife) – there are also many specialized knives that are designed for specific tasks. Kitchen knives can be made from several different materials.
Carbon steel is an alloy of iron and carbon, often including other elements such as vanadium and manganese. Carbon steel commonly used in knives has around 1.0% carbon (ex. AISI 1095), is inexpensive, and holds its edge well. Carbon steel is normally easier to resharpen than many stainless steels, but is vulnerable to rust and stains. The blades should be cleaned, dried, and lubricated after each use. New carbon-steel knives may impart a metallic or “iron” flavour to acidic foods, though over time, the steel will acquire a patina of oxidation which will prevent corrosion. Good carbon steel will take a sharp edge, but is not so hard as to be difficult to sharpen, unlike some grades of stainless steel.
Stainless steel is an alloy of iron, approximately 10–15% chromium, possibly nickel, and molybdenum, with only a small amount of carbon. Typical stainless steel knives are made of 420 stainless, a high-chromium stainless steel alloy often used in flatware. Stainless steel may be softer than carbon steel, but this makes it easier to sharpen. Stainless steel knives resist rust and corrosion better than carbon steel knives.
High carbon stainless steel is a stainless steel alloy with a relatively high amount of carbon compared to other stainless alloys. For example, AISI grade 420 stainless steel normally contains 0.15% by weight of carbon, but the 420HC variant used for cutlery has 0.4% to 0.5%. The increased carbon content is intended to provide the best attributes of carbon steel and ordinary stainless steel. High carbon stainless steel blades do not discolour or stain, and maintain a sharp edge for a reasonable time. Most ‘high-carbon’ stainless blades are made of more expensive alloys than less-expensive stainless knives, often including amounts of molybdenum, vanadium, cobalt, and other components intended to increase strength, edge-holding, and cutting ability.
Laminated blades combine the advantages of a hard, but brittle steel which will hold a good edge but is easily chipped and damaged, with a tougher steel less susceptible to damage and chipping, but incapable of taking a good edge. The hard steel is sandwiched (laminated) and protected between layers of the tougher steel. The hard steel forms the edge of the knife; it will take a more acute grind than a softer steel, and will stay sharp longer.
Titanium is lighter and more corrosion-resistant, but not harder than steel. However it is more flexible than steel. Titanium does not impart any flavour to food. It is typically expensive and not well suited to cutlery.
Ceramic knives are very hard, made from sintered zirconium dioxide, and retain their sharp edge for a long time. They are light in weight, do not impart any taste to food and do not corrode. Suitable for slicing fruit, vegetables and boneless meat. Ceramic knives are best used as a specialist kitchen utensil. Recent manufacturing improvements have made them less brittle. Because of their hardness and brittle edges, sharpening requires special techniques.
Plastic blades are usually not very sharp and are mainly used to cut through vegetables without causing discolouration. They are not sharp enough to cut deeply into flesh, but can cut or scratch skin.
Steel blades can be manufactured either by being forged or stamped.
Hand forged blades are made in a multi-step process by skilled manual labor. A chunk of steel alloy is heated to a high temperature, and pounded while hot to form it. The blade is then heated above critical temperature (which varies between alloys), quenched in an appropriate liquid, and tempered to the desired hardness. Commercially, “forged” blades may receive as little as one blow from a hammer between dies, to form features such as the “bolster” in a blank. After forging and heat-treating, the blade is polished and sharpened. Forged blades are typically thicker and heavier than stamped blades, which is sometimes advantageous.
Stamped blades are cut to shape directly from cold-rolled steel, heat-treated for strength, then ground, polished, and sharpened. Stamped blades can often, but not always, be identified by the absence of a bolster.
Type of edge
The edge of the knife can be sharpened to a cutting surface in a number of different ways. There are three main features:
the grind – what a cross-section looks like
the profile – whether the edge is straight or serrated, and straight, curved or recurved
away from edge – how the blade is constructed away from the edge