Making sense of steelMay 08 '07 Write an essay on this topic.
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The Bottom Line Almost everything you hear about knife steel is meaningless or misleading. Here's how to think about steel in the kitchen.
When it comes to kitchen ware, no subject is more full of bluster, ballyhoo, and outright BS than what knives are made of. Put all the advice you have ever heard about knife steel together, and it's worth about the same as a Hefty bag full of floor sweepings. Simple declarative statements on this subject should be viewed with extreme caution, if not dismissed with frank contempt. Knives made of this kind of steel can't be sharpened. Knives made of that kind of steel will hold an edge. Knives made of another kind can be put in a dishwasher. Yet another kind "can't be forged." Do buy this kind, and don't buy that kind. You need to know only one thing about all such attempts to boil this area of metallurgy down into a soundbite: They are just wishful thinking. Manufacturers make it worse. At first glance, they seem to offer two kinds of steel, high-carbon and stainless. What a beautiful world it would be if it stopped there, or if those two terms referred to particular materials in the real world. But as if to illustrate that they don't, manufacturers come at us with high-carbon stainless, stain-free, and my favorite, high-stainless carbon, in addition to seemingly infinite variations on these themes. The reason these terms are so perplexing is that they don't mean a whole lot. At best, they are vague gestures at groups of possible materials whose definitions are highly technical and very boring. At worst, marketing departments just make them up. "Surgical steel" is one of those terms that simply doesn't mean a thing other than "steel." It doesn't mean good knife, bad knife, or mediocre knife. It doesn't mean anything. Any utterance containing the term should be ignored. Manufacturers help matters a little when they specify a standardized designation for the steel they use, such as 420, 440-A, 1095, O-1, D2, and so on. If you're a bit of a geek, and you really care, then such designations can tell you some things about the composition of the raw material the knife started from and some characteristics the knife is likely to have, such as hardness, toughness, and resistance to stain and corrosion. But even the technical designations do not tell you everything you need to know about these things, and there are no rules that say "buy this kind" or "do not buy that kind." The fact is that all name-brand and even most off-brand kitchen cutlery is made of materials that are generally suited to the purpose. Whether you wind up with a good knife or a bad knife depends on a bunch of factors quite apart from the raw material, including such vagaries as your personal preference and what you plan to use the knife for. For example, people often claim that a knife made of this or that material will or won't hold an edge, break or chip easily, or be sharpenable. They are talking about the steel's hardness and toughness. Generally, the more you have of one, the less you have of the other. Generally-- not always, but generally-- a harder steel will hold an edge better than a softer one, but will chip or break more easily and will be harder to sharpen. Stands to reason, right? Hard is brittle, and soft is tough. But the steel designation, although it may tell you the exact composition of the steel, will not tell you how hard or tough it is. It will only give you a range of how hard that steel can be. How hard it actually is depends on tempering, which is to say heat treatment, which is done at the point of manufacture. Thus, the same steel may vary widely in hardness from factory to factory, use to use, day to day, or even knife to knife. A knife made of the most hardenable tool steel will fold over like pig iron if it is improperly heat treated. Whether or not it will chip or break depends not only on hardness but on a number of things occurring all the way down to the molecular level. A consumer at the point of sale is in no position to determine such things. The best we can do is look at the material, the blade design, the company's reputation for quality control, and our intended use. Then we make an educated guess. We try a bunch of different knives, and the proof is in the using of them. The "best" knives for a particular user will find their way to the top of the knife drawer, usually without regard to what they're made of or how much they cost. I know that's vague, but the truth is that there's no formula matching raw materials to particular knife qualities, much less traits like "good" or "bad." Still, we can say some useful things about the different steels typically used in kitchen cutlery without falling prey to oversimplification. Let's go back to that false duality, high-carbon versus stainless steel. Yes, manufacturers muddle the issue with terms like "high-carbon stainless," but the truth is that it's useful to think of steel as being either one or the other, and in those terms, "high-carbon stainless" is stainless. To make any sense of this whatsoever, it is necessary to know what steel is. That's easy: Steel is iron with carbon in it. Imagine melting down a cast iron skillet over a charcoal fire and you're close to knowing how to make steel. In a sense, all steel is "carbon steel." It all has some carbon in it-- anywhere from .02% to 1.7% by weight. The carbon makes steel harder than iron, which is important if you want a knife that stays sharp. A pure iron knife would be better than one made of wood or rubber but would probably disappoint a modern consumer. Besides iron and carbon, a bunch of other stuff might be found in steel, including manganese, molybdenum, tungsten, silicon, nickel, and vanadium. Mostly, these elements contribute to a steel's hardenability and toughness by influencing the way the microscopic grains of steel are formed. Let's leave that to the science geeks and consider the most important additional element for our purposes, which is chromium. The most important thing chrome does is add resistance to rust and corrosion. Any steel that is composed of 13% or more chrome is designated "stainless." That's it. That's the magic formula. 13% or more chrome is stainless, and anything less is not stainless. That's all the term means, and it doesn't mean anything else. Remember that when marketers try to confuse you. Usually, they will call anything that isn't stainless "high-carbon," and that's why it's useful to think in terms of that duality, even though stainless may have a high amount of carbon in it. To sum it up, steel is either stainless, or it isn't. But is "stainless," in fact, stainless? No. Any steel will rust under the right conditions. Stainless is just less apt to rust than steels with less chrome. Common stainless steels for kitchen knives include 420, 440 (A, B, and C), and anything that starts with AUS or ATS, followed by digits. The thing to know about these metals is that they're stainless. That means they're less prone to rust, of course, but one thing more. Stainless is trickier than some "high-carbon" steels to make both hard and tough at the same time. Often, there is a compromise between edge-holding and toughness, or sharpenability and edge-holding. And variations in quality control tend to be fatal to a stainless knife's usability. All this is the case with all knife steels, but more so with stainless. Very poor stainless is irredeemable junk, and there's a lot of it around. I think that's what has given stainless knives such a poor reputation. It's not that stainless is junk, can't be sharpened, can't hold an edge, is too soft, is too brittle, or any of that. Millions and millions of perfectly good stainless steel knives are put to use by professionals every day in kitchens, canneries, fisheries, butcher shops, and delis around the world. It is just that stainless is hard to get right, and so a lot of manufacturers get it wrong. But stainless is not synonymous with cheap. There are some expensive and extremely durable grades I call "boutique" steels, like S30V, the presence of which strongly indicate a manufacturer who cared enough to get it right. Why would they bother using gold only to make junk? But even boutique steel is no guarantee that a given knife is "better" than another one made of common 420 or 440 stainless. That means that when you buy a knife in stainless, you either go with a company whose reputation is immaculate, or you take a chance. After that, either the knife holds up, or it doesn't. The same goes for "high-carbon" knives, only less so. If the knife is made of "high-carbon" steel, the chances are good that it was manufactured with sufficient care to result in a decent product. It's still no guarantee of quality, durability, sharpness, sharpenability, suitability to any particular purpose, or anything else. It's just a good sign. If it guarantees anything, it's that you should wipe the knife with a light coat of mineral oil to prevent rusting. Common high-carbon grades include the range from 1095 (which means .95% carbon) to 1050 (.50% carbon), O-1, 51 or 52 followed by two or three digits, and the extremely hard "semi-stainless" tool steels such as D2, among many others. If you collect knives, it may be a good idea to become familiar with the more prized high-carbon steels so that you can identify a bargain when it comes along. You will hear the opinion that you can't sharpen stainless knives. That's baloney. I do it every day, often on knives that cost less than $5, and always on gadgets costing $10 or less that require no expertise. Sharpenability does depend somewhat on hardness, and sometimes stainless is very hard and very brittle, but the tungsten-carbide or diamond-coated sharpening gadgets are harder. Sharpness and sharpenability, in my experience, come more from the design of the blade than the steel it's made from. So if you want to buy a knife, consider the steel if you want to, but first, consider which knives are used and praised by persons who make their living with knives. Not surprisingly, you will find proponents of Henckels, Wusthof, Shun, and other pricey, forged, high-carbon knives. But you'll find even more die-hard users of Forschner and Dexter-Russell, whose knives look like everything we're told to avoid and sell for embarrassingly cheap prices. Some swear by even less expensive knives such as Old Hickory and Ontario work knives. I can vouch for these. They are not so much "cheap" as they are a simple thing done right. And every Thai kitchen is stocked with cleavers and paring knives by companies like Kiwi, whose wares are available at Asian groceries for almost nothing. None of these users follow any hard and fast rule about steel, and neither should you. One last word. People may say that some steels are "dishwasher-safe," and others aren't. Bull. You should never put any knife that you want to keep sharp into the dishwasher. Steak knives and butter knives, OK. Knives that are really more like saws or spatulas than cutlery, OK. But for real knives, no matter what they're made of: use, wash, dry, and put away. Period.  |
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