Your Edge (and How to Keep It)

When you visit a doctor with an ailment, the doctor will ask questions and maybe run a few tests before making a diagnosis. If you come to me and ask me to sharpen your knives, I will also ask you a few questions and maybe run a couple of tests. And once we agree on the condition of your knives, we will have to work out a treatment plan. This may include sharpening, but it may also include changing the way you use a knife.

First we have to agree that we cannot agree as to what the word sharp really means. Although we tend to use the term sharp as an absolute, this is not the case. The states of sharp and dull blend together seamlessly and form a continuum. A particular knife may be dull to me and sharp to you, or vice versa. Do you agree?

Next, when you use a knife, do you slice or chop? More specifically, do you use your blade in a sawing motion with a light downward pressure or do you try to push your knife downward through the food you are cutting? Under a microscope, the sharp edge of a knife will appear rough, not smooth. The roughness can have a number of configurations, depending on how the blade was last sharpened; all will be rough enough to appear somewhat like the blade of a saw. When a knife is used in a motion similar to a saw, i.e., pushed back and forth, it will feel much sharper than if you try to push it through the food. Your knife may not need sharpening as much as your technique may. And if you chop with your knife instead of slice, the edge will dull faster.

Assuming that you use the proper technique, I next have to ask: Are your knives made from a material that can be sharpened easily? Most knives of moderate to good quality are nowadays made from high-carbon stainless steel, a material with enough hardness to take an edge. High-carbon steel blades, the type that stain, can also be sharpened very nicely. But the soft, plain stainless-steel blades common in some grocery-store kitchen knives are virtually impossible to sharpen. (There are also knives with ceramic blades that come from the manufacturer very sharp; if they become dull, only the manufacturer can sharpen them.)

Do you take good care of your knives? Why should I sharpen your knife if you don’t make the effort to keep your knives sharp? Do you always cut against a wooden cutting board? The softer the cutting board, the easier it is on the knife. I prefer an end-grain wooden board made from a relatively soft wood, but even an edge-grain hardwood board is acceptable. I am not a fan of plastic boards, and I definitely recommend against the use of glass, marble, metal, and bamboo cutting boards. (I also don’t like lightweight cutting boards of any material—that can slide on your work surface—but this is more for safety than for maintaining the sharpness of your knife.)

When you use your knife, do you keep it clean by wiping off any food or grease clinging to it? I do this with a damp towel folded over and placed flat on the table. After you finish using your knife, do you wash it with hot water and dry it immediately with a towel? You should. Good knives should never be placed in the dishwasher—even if the manufacturer says that you can. Dishwasher soap can erode the cutting edge and seriously dull a knife. Also, you should never just place your dirty knife in a sink or a pan of soapy water or leave it to dry in a dish rack; this is for safety more than a matter of maintaining sharpness.

How do you store your knives? Are the cutting edges protected in storage? I prefer individual plastic sleeves that slip onto each blade, and then I store my protected knives in a drawer. But there are many other systems that will also protect a knife and maintain its sharpness. Knives should never be stored loose in a drawer with their blades unprotected. It is also best not to store them with the blades resting on their cutting edge.

Now that we know you are using your knife properly and taking good care of it, I will assume that your knife really is dull. But what is dull? It’s the state where each of us, as individuals, determines that our knife is not sharp. There can be a couple of reasons why you think your knife is not sharp. The most common one is that the very tip of the cutting edge is pushed or roll over to one side or another. For a cutting edge that is ground to a fine angle, the absolute edge may actually be a burr produced by the grinding process or a previous sharpening; for blades with heavier edges, it will be just the little pieces of metal that stick out after the grinding. Those little pieces of the edge that make it resemble a saw blade don’t work very well when pushed to one side or another, and the burr can be rolled to one side, too.

If all that is needed is just a straightening, the job calls for a “steel.” This is that round rod that your father used to slide the carving knife over a number of times before massacring the Thanksgiving turkey. Nowadays, steels are also available with a flat cross-section and with a very fine abrasive coating. All the steel does is straighten the cutting edge—even those with the fine abrasive coating. They are not designed to remove metal from the blade—only straighten the edge.

When used properly, a steel can restore the knife’s edge to one that, when used properly, will feel sharp to you. But what is properly? Use of the steel can be a problem as well as a solution. To work effectively, the knife’s cutting edge must slide along the steel as close as possible to which the angle the edge is ground. Most manufacturers do not publish the grinding angle they set on their knives. And if your knife has been sharpened since it was purchased, it may have been reground to a new angle. Sometimes this second condition is an advantage because it may be easier to determine the grind angle by looking at the sharpening machine. Once you know the grind angle, you’re ready to start steeling, or honing, your knife.

I have seen three principal methods of steeling and many variations. My preferred method is with the steel held in your non-knife hand, pointed away from your body horizontally and about 45 degrees from being parallel with your shoulders. Hold your knife in a pinch grip, with the cutting edge directed toward your body. Starting with the heel of the blade near the tip of the steel, the cutting edge is drawn across the steel while holding the blade at the grind angle to the steel; the blade is moved down the steel so that by the time the tip is drawn across the steel, it is near the handle of the steel. Steel the sides of the cutting edge alternately, and repeat the process three to five times. With this technique, you will tend to point the steel slightly upward when the blade is on the bottom and slightly downward when the blade is on the top; your wrists will flex and your forearms will rotate to adjust the angle. Even though the cutting edge of the blade is pointing at your belly, the hilt of the steel will protect your body from injury should the knife slip. If your knife has a full bolster, one that extends all the way from the spine to the edge, you will not be able to steel the full heel of the blade.

Some people recommend a variation on the above method, with the cutting edge directed away from the body. I don’t like this method because it is harder to hold the cutting edge at the equivalent angle when switching from one side of the blade to the other. For this method, most of the flexing and rotating is done with the hand holding the knife in an awkward manner. Yet another variation is to hold the steel vertically with the tip against the work surface. The blade is drawn across the steel with the cutting edge pointed down, switching from side to side after each pass. Again, it is difficult to maintain the same angle on both sides of the blade. The second and third methods are often suggested by teachers and manufacturers to alleviate your fears of steeling with the blade toward your body (and possibly limit their liability.) But these alternative methods, at least in my hands, generally do not work as well as my preferred method.

Sooner or later, no matter how much you steel your knife, it will no longer have any effect. This is because the cutting edge has become rounded. When this occurs, the only solution is to regrind the edge—this process is called sharpening.

There are many methods available for sharpening knives—some complicated requiring patience and experience, others simple and almost trivial. But choosing the method right for you and your knives is not trivial. The most important thing to remember is that the edge will be reground during the sharpening. Thus, for the method you chose, it is necessary to regrind the edge to its original angle, that is, unless you want to intentionally change the angle.

Do you know to what angle your knife edge is currently ground? Probably not. Most manufacturers do not publish this information, or publish conflicting information. (Wüsthof instructs the users of one of its sharpening stones to hold the blade at a 10 to 15-degree angle, but for another, specifies a 15 to 20-degree angle. However, they say that any of their knives can be sharpened on either stone. (I have heard from one of Wüsthof’s competitors that the company usually grinds the cutting edge on their knives to 22 degrees.) A narrow angle will produce an edge that feels sharper, but a wider angle will produce a stronger edge that will last longer.

The sharpening method that I hear recommended by knife experts most often is to leave the process to a professional, and, for the most part, this is good advice. Knife sharpening is an art that requires much experience. But how do you choose which professional to go to? Ask the chef at your favorite restaurant. As a professional who uses knives for many hours each day, he or she should know a competent sharpening professional. Then go and talk to the person actually doing the sharpening. Maybe even ask to watch the professional sharpener work for a few minutes. Ask the sharpener about his or her personal philosophy of knife sharpening. Is the sharpener a craftsman hand-holding the blade on a grinding stone or belt, or simply passing the knife through a machine? If your knife has a bolster, will the sharpener reshape that as necessary along with the edge? Does the sharpener grind all edges to the same angle? These are all questions to consider. Avoid sharpeners who simply pass the blades through a machine; the results may be less than optimal.

If you are like me, you’ll distrust the “professionals” and sharpen your knives yourself. I also do it myself because I want my knives sharp immediately. I don’t want to deal with the expense, time delay, and inconvenience of sending my knives out. Also, I’ve invested a lot of money in my knives, and I don’t want to take the chance of others possibly ruining them.

So now that I have chosen to sharpen my knives myself—how can I do that? There are many methods and systems to choose from. Use a whetstone? Use an electric sharpener? Use a draw-through device? Go cheap? Go Expensive?

As discussed earlier, once I touch my blade to a sharpener, I’ll be reshaping the cutting edge to match the sharpener. Consequently, I’ll want to choose a system that makes it easy to grind a constant angle. This pretty much eliminates a conventional whetstone because with a stone I have to rely on my judgment to maintain a constant angle. With all home-style sharpening systems, it is important to read and understand the manufacturer’s instructions for the system chosen.

There are also systems where an abrasive rod is placed at a fixed angle. The knife blade is held vertically and is stroked across the rod. Although it is easier for you, or me, to hold the blade vertically than at an odd angle, there will still be some difficulty holding it at a fixed angle.

Another type of manual system clamps the blade at a fixed angle to the abrasive. This system solves the problem of consistency, but if your knife is long, an error of up to a couple of degrees can be introduced. Thus, it is necessary to sharpen your knife in sections. A further problem for me with this type of system is that I have to assemble a lot of pieces to sharpen a knife. This makes the system inconvenient if I need to sharpen my blades while I’m cooking.

I have found one system that solves many of my problems. It’s a unique sharpener produced by Füritechniques called the OziTech. The device is able to maintain a constant 20-degree angle on each side of the blade without any particular effort in the part of the user. The sharpener is pocket-sized, making it very portable and easy to use in a busy kitchen environment.

But what about electric knife sharpeners? For years, I’ve also used an electric sharpener with moderate success. My particular model is not as convenient to use as the OziTech, but when I need to sharpen a truly damaged edge, this machine comes to the rescue.

All of the above sharpening systems have one shortcoming. If your knife has a full bolster and it’s designed for use mostly on a cutting board, such as a chef’s knife, these sharpening systems cannot remove enough metal near the heel of the knife so that the cutting edge no longer touches the board—the knife is no longer effective near the heel of the blade. This is a circumstance that a professional sharpener can overcome by removing metal from the bolster at the same time the blade is being sharpened.

There are many methods available to you to sharpen your knives, and whichever you choose, remember that once you have sharp knives, it is your responsibility to care for the edges. They are your edges to keep sharp.

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©2007 Peter Hertzmann, Inc. All rights reserved.

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