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A good set of kitchen knives is arguably the most important tool in any chef’s arsenal. No matter what is being cooked or prepared, it is inevitable that there will be some sort of cutting or chopping involved at some point, and those who have spent any time in a kitchen know how important it is to maintain the blades on your knives. Dull knives will not cut effectively and can be tiresome or even hazardous to use in situations that require precise and careful cuts. Keeping your knives sharp is a necessary routine for any amateur, professional, or home chef, but it is critical to your knives’ longevity that they be sharpened properly. Although they are used for all sorts of heavy-duty tasks in the kitchen, knives are actually fairly delicate implements, and improper or overzealous sharpening of a blade can be more detrimental than the wear from any period of use. Many restaurants and commercial kitchens regularly outsource their knife sharpening to a professional third party, but taking measures to keep your blades sharp on your own is an easily achievable way to avoid having to constantly send your knives away to be restored.
The first thing to understand about knife sharpening is the process itself. General knife sharpening is broken down into three sub-steps: sharpening, straightening, and polishing. These three steps are also often referred to as grinding, steeling, and stropping, respectively. Each of these three steps can be performed independently of each other if the blade has been well maintained and does not require a complete restructuring, but a heavily worn or blunt blade will likely require all three steps.
Sharpening (Grinding):
Sharpening is the most extreme step in restoring the edge of your blade. In sharpening, a hard, abrasive material (typically stone) is used to grind away metal from the blade of the knife to form an entirely new cutting edge. Professionals often use a rotating grinding wheel to sharpen knives quickly and efficiently, but the same effect can be achieved with a bit more time and persistence on a flat whetstone. Grinding is the most direct method of sharpening a blade, and it can often be the only way to restore heavily worn or blunt knives. Optimally, however, it should only be performed a few times a year on most kitchen knives. Sharpening your knives too often will reduce their lifespan (particularly with small knives), as each sharpening removes a bit of material from the blade. With a routine straightening schedule, most knives can be maintained for longer periods without the need for frequent professional sharpening.
Straightening (Steeling):
Straightening (commonly referred to as “honing”) is the second step in the knife sharpening process. In straightening, the knife blade is rubbed against a sharpening steel or honing rod to realign the edge of the blade without removing a significant amount of material. Steels (the materials of which most knives are made) tend to be very malleable materials, and the edge of most kitchen knives will begin to deform after just a few uses. While the blade may look contiguous to the human eye, the metal’s edge is actually made up of countless “micro-serrations” and tiny breaks in the material. These microscopic teeth will begin to bend and curl under the forces of repeatedly coming into contact with various types of food and cutting surfaces, therefore hampering the knife’s ability to “grip” the surface of the food and ultimately reducing its overall efficacy. A knife with such a deformed edge is often referred to as having a “turned” blade. Using a honing rod or sharpening steel to straighten your knife before or after each use realigns the material on the edge of the blade and will prevent the blade from turning significantly between routine sharpening.
As mentioned before, frequently straightening a blade will reduce the necessity for excessive sharpening by grinding. The ultimate goal in preserving the sharpness of your knives is to minimize the amount of pressure exerted on the blade of the knife. A turned knife will require more input force from the user, which is translated into increased pressure against the blade that causes extra wear over time and – if left unchecked – will require the edge to be fully reformed more frequently. The easiest way to keep your knives in check is to simply make a habit of honing and rinsing your knife immediately before each time that you use it. However, if you straighten your knives less often than you use them, a good test for determining whether or not your blades need to be honed is the “bite test.” A knife’s “bite” is a measure of its capacity to begin cutting an object without any downward pressure exerted by the user. A properly sharp knife will, when drawn across the surface of a tomato, begin to cut under the force of its weight alone. Any number of vegetables can be used (carrots, cucumbers, etc.) to perform the bite test, but tomatoes are most common due to their uniquely resilient outer skin. Effective knives should require little effort from the user to cut most common ingredients, so if using your knife requires excessive or uncomfortable force, a quick but careful straightening may be in order.
As a side note, there is often some confusion about the true meaning of the term “hone.” Common convention takes “hone” to mean strictly “straightening,” while subtractive grinding is exclusively referred to as “sharpening.” However, the term “hone” is somewhat ambiguous, as it can also be used to refer to sharpening by grinding using a high or fine grit material (the result of which is more similar to straightening, as it removes a minimal amount of material).
Polishing (Stropping):
Polishing a knife is the final step in blade sharpening. This step is optional, and is often skipped when sharpening knives used in less demanding environments such as residential kitchens. Polishing is usually performed using a leather strap that has been impregnated with abrasive compounds (called a “strop”), but several other more common materials such as paper and cloth can be used instead. Polishing the blade further straightens the edge of the knife without removing material to ensure that the highest possible amount of edge contact is being made with the surface to be cut. Polishing can also restore the smooth mirror finish to a used blade, making it easier to keep clean.
Well-kempt knives are one of the most important tools in any kitchen, and those who cook as a profession or a serious hobby are likely to run up a significant bill buying strong, high quality knives. Keeping your knives properly sharpened does require fairly constant attention, and while it may seem like a chore at times, it is necessary if you are to get the most out of your investment. A properly maintained kitchen knife will last for quite some time and will reduce the risk of botched cuts and potential hazards (dull knives have a tendency to slip) in your kitchen. But with a bit of time and care, your knives are sure to become the most trusted part of your kitchen toolset.
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