Carbon Steel: Why People Still Choose It

By definition, carbon steel is steel with a carbon content between 0.05% and 2.1%. In practice, makers rename anything that is not stainless steel as carbon steel for convenience. That accounts for half the confusion later sorted out in arguments.

What carbon does

Carbon is the element that gives a knife its hardness. Almost every other addition makes the steel more stainless or stronger, but it does so at the expense of hardness. And hardness converts into cutting directly: the harder the knife, the thinner you can grind it and the sharper it comes out.

The price is susceptibility to rust and high brittleness. So a genuinely good carbon steel is not “more carbon” but a balance: high carbon content with minimal additions such as cobalt, molybdenum or vanadium.

Strictly speaking, a carbon steel is one alloyed only with carbon, manganese and silicon: 1084, 1095, W1, White #1. As soon as there are more alloying elements, the steel is called alloy steel — 52100, 5160. More still, and it is tool steel or high-alloy tool steel: A2, D2, CPM-10V, Vanadis 8. Some grades sit between categories: O1 and L6 are formally tool steels but closer to alloy steels in composition. W1 manages to be both a tool steel and a plain carbon steel at once.

This is not pedantry, it is the heart of the matter. 1095 and CPM-10V are both non-stainless, and the resemblance ends there. 1095 needs a water quench or a fast oil quench; 10V reaches hardness in plain air. In 1095 the carbides are iron carbides — cementite; there are not many of them and they are comparatively soft, so wear resistance is low. 10V has plenty of very hard vanadium carbide, and wear resistance is very high. A smith works 1095 easily; 10V gives him roughly the same misery as any stainless. So “carbon steel” is not a simple group, it covers a wide range of properties, and the “stainless versus carbon” argument is too crude.

How it behaves

Carbon steels contain less carbon than typical stainless steels, but in them carbon is the main alloying element. The structure comes out more uniform than in stainless and other high-alloy steels: carbides are present only as very small inclusions in the iron.

Everything else follows from that. The material is usually a little harder than standard stainless such as ST-304 — high-quality alloys excepted — and therefore holds a sharper, straighter edge without rolling it on contact with hard materials. But it goes blunt from abrasion faster: it has no hard inclusions able to stand up to friction. The flip side of the same property is that it is easier to sharpen and less resistant to chipping.

Carbon steels contain no chromium, which makes them very prone to corrosion. That is not a flaw of the grade, it is its definition.

What has changed

Carbon steel used to be far stronger, longer-lasting and easier to sharpen than stainless. That stopped being true with the arrival of modern alloy metallurgy — powder steels such as VG-10 and SG-2. These high-quality stainless alloys gathered everything at once: hardness, impact toughness and corrosion resistance, and moved past the limits of carbon steel.

The only advantage carbon steel retains over good stainless alloys is production cost. It is far cheaper to make. That is why knives made from it are usually inexpensive, and why it remains the standard choice for rough work and budget lines.

Where it is genuinely at home

Canteens, restaurants and supermarket meat counters work with carbon steel knives, and with knives made from rolled stock rather than forged. The first reason is price. The second is how the work is organised.

In a professional setting there is no “one special knife”. For hygiene and to save time on deep cleaning, each type of product has its own knife, outwardly indistinguishable from the rest, marked only with a code: RF for raw fish, CM for cooked meat, RV for raw vegetables. It lives in its own place, marked the same way. Only a mentally unwell restaurant owner would buy seven or eight identical luxury-class knives of each type for every cook.

Maintaining such a fleet demands exactly what carbon steel likes. The cook touches up the knife on a steel constantly: truing the edge before every return to the station, in a motion worn down to automatic, strikes nobody as a problem. And no professional will leave a knife to rust — he will wash it, wipe it, lightly oil it with unsalted food fat and put it back.

The smoker’s boning knife

Constant sharpening has a side effect. The blade wears away, becomes thin and gradually thickens towards the handle. The shape is distinctive, and it has bred a consumer stereotype: a knife of that shape is considered “sharper”.

Knives made in that shape from the start were named boning knives by the marketing department. Although the only thing required of a boning knife is a short length combined with a degree of blade flex. In truth, a heavily worn knife (or one that a marketer has worked on) is simply good for nothing else: it can no longer sit flat against the board, and boning is all it has left. The difference is visible in image search results: a proper boning knife is short and thin, while its opposite looks worn down, with an incongruous and technologically inexplicable bolster at the start of the heel.

Carbon steel, in short, is still chosen not for romance and not for “real cutting”. It is chosen for cheapness, for easy sharpening and for the fact that it honestly repays regular care. Where there will be no care, there is no reason to choose it.