Ever make cookies? Then you know how any single recipe can produce a markedly different result. Kitchen blades' primary component -- steel -- can be created with any number of different recipes, each resulting in a blade with unique properties.
Depending on the recipe used, a steel will have a varying degree of "hardness". Hardness in kitchen knives is a good thing -- the harder a blade, the sharper an edge it can tolerate. Just like with cookies, though, too much of a good thing can be overkill. Blades that are too hard can be brittle and prone to breaking or even shattering. Ceramic blades have become less popular in recent years due to their brittleness. Drop a ceramic knife on the floor and you're out your $300.
Hardness is measured on the Rockwell Hardness Scale (HRC). Measurements are typically in the 55-60 range. Some of the sharpest Japanese knives are hardened to an HRC of more than 60, while Wusthof and Henckels knives are typically closer to 55. It might not sound like much, but a few points on the Rockwell scale can make a big difference.
Blade hardness is probably the biggest difference between Japanese and German knives. Japanese knives are hard, sharp surgical instruments. They are razor-sharp but require careful handling. German knives are duller but require less maintenance. See The Rise and Fall of The Great Knife-Makers for more on this distinction.
Steel always contains iron and carbon. Carbon facilitates the transformation of iron into hardened steel. Some of this carbon is absorbed by the iron, but the rest adds hardness to the blade. The more Carbon, the harder the blade.
You'll hear knives described as "High-Carbon". This is a good sign -- it means that the manufacturer is at least trying to make a hardened blade -- but it's often not enough to distinguish a sub-par blade from a high-quality one. Carbon typically makes up somewhere between 0.5% and 1.5% of a High-Carbon blade.
Beyond iron and carbon, there are several popular additives that contribute various properties to kitchen blade steel.
Chromium adds hardness, like carbon, but also allows the knife to "hold an edge". This means that the knife can more easily be sharpened and will retain its edge for a longer period of time. Chromium can also contribute to rust-resistance, so is commonly used in stainless steels.
Vanadium allows a knife to retain an extra-sharp edge, while Molybdenum and Manganese contribute hardness and wear-resistance.
If I told you I was making Toll House Chocolate Chip Cookies, you'd have a pretty good idea what I meant. Just like with cookies, there are some mixtures of steel that are so frequently used, they've become recognized as "standard" steels.
Here's a rundown of just a few of the most commonly-used recipes for making kitchen knives:
- SG-2: The current top dog of kitchen blade steels. This is a "powdered" steel rather than a "folded" steel. This allows for more uniform distribution of the steel's ingredients and allows the blade to hold an extra-sharp edge. Shun Elite knives use this steel and are some of the sharpest knives available. These knives are hardened to a Rockwell Hardness rating of 64.
- VG-10: A premium steel. Contains chromium, vanadium, molybdenum and cobalt. Due to import restrictions, this steel has traditionally been used only by Japanese knife makers. Its most striking property is supreme sharpness, though it is also tough and holds an edge extremely well. You may encounter a variant of VG-10 called VG-1. This is another high-end steel, but is typically not quite as sharp as VG-10.
- 440/440A/440B/440C: These are high-carbon alloys, with increased carbon content as you work your way through the alphabet. 440A is barely acceptable for a kitchen blade, while 440C can be used to produce a high-quality blade. If a blade is marked "440" it is probably the less-desirable 440A variation.
- X50CrMo15: You'll see this type of marking, or variations of it, to indicate each individual element contained in the steel. Wusthof and many others mark their knives this way. The two digits after then X indicate the percentage of Carbon in the steel (X50 means 0.50%, X75 means 0.75%, etc.). The final two digits indicate the percentage of all the other elements combined. Cr indicates the presence of Chromium, Mo indicates Molybdenum, while V indicates Vanadium.
Almost as important as the materials used to make a blade are the techniques used to form and shape it. Unfortunately, there is so much marketing mumbo-jumbo mixed up in describing the treatments, it's almost impossible to make any sense of it.
In general forged knives are considered to be higher quality than stamped ones. How a blade is hardened is as important in determining its hardness as is the materials used. You'll encounter the term "drop-forged" which means the heated knife is crushed under an enormous hammer, though in practice very few blades are actually hardened this way. You'll also hear that knives are "ice hardened" or "vacuum treated". Any of these techniques can be used to produce a quality knife.
What's All This Got To Do With Saving Money?
Ah right, you came here to save money! Well, here's the thing -- a little education can go a long way. Now that you know something about steel, you can start to evaluate knife blades and decide which ones are for you. But don't go by price or by name brand -- go by steel.
Looking for a Chef's Knife in the $20 range? You're going to find a lot of junk down at that end of the spectrum. But find one with X50CrMo15 steel and you've got yourself a great value. Keep that knife sharp and you've just saved yourself 50% or more.
Want to step up to some high end knives? If you're going to shell out $100 for a Santoku and you're willing to care for it properly, a MAC knife hardened to HRC 60 and sharpened appropriately will be a stunning value. You can save 50% over a high-end Wusthof and get a better knife to boot.
This was probably more than you ever wanted to know about steel. But there's always more to learn, even without getting a PhD in metallurgy. The FAQ at ZKnives.com is an excellent resource that provides quite a bit of depth.