This topic is locked
By Chad Ward (Chad)
Warning: Remember that handling, using and sharpening knives is inherently dangerous. Neither eGullet nor the author can be responsible for your safety. That’s your job. Knife safety, especially during sharpening, is a matter of common sense. Keep your fingers, toes and everything else out of the path of the blade – even if it were to slip. If you go slowly, pay attention and stay focused, you’ll be fine.
Table of Contents
Introduction
Section One: The Sad Truth about Kitchen Knives
Section Two: Steel
Section Three: Edge Basics
Section Four: Sharpening Basics
Section Five: Sharpening Step by Step
Section Six: Maintenance
Section Seven: Overview of Sharpening Systems
Section Eight: Conclusions and Resources
Introduction
“Knife sharpening is hard.”
“Sharpening is too difficult and time consuming to do at home.”
“Send your knives to a professional sharpener once a year and you will be fine.”
“You have to spend hours hunched over a heavy hone slathered with oil.”
This well-intentioned advice is parroted in cooking schools, Food Network television programs, professional manuals and cookbooks. And it is just plain wrong.
Okay, maybe not so much wrong as misleading.
Knife sharpening is not difficult. It is not shrouded in mystery. With a little knowledge, a little geometry, a couple of tricks and some inexpensive tools, knife sharpening can be fairly easy and extremely rewarding. At the very least it’s a great skill for the toolbox. You’ll come away from this clinic with a better understanding of edges, steel and how to maintain your knives yourself. Or, if you decide to send them out, you’ll know how to make sure you’re getting what you want – and what you pay for.
Section One: The Sad Truth About Kitchen Knives
To a chef, there is nothing more important than his knife. It is not only an extension of his hands, it is an extension of his very personality. The knife is a chef’s paintbrush.
So why are most kitchen knives so bad?
The knives found in most commercial and home kitchens are designed for the lowest common denominator. The manufacturers of these knives make a series of compromises calculated to keep the largest number of people happily using their knives for the longest period of time. Like supermarket tomatoes bred for sturdiness and uniformity rather than flavor, these compromises seriously degrade the performance of your knives.
The first compromise begins with the steel. Steel is the heart of the knife. Most manufacturers (Henckels, Wusthof, Forschner, et al.) have proprietary steel blends and are very close-mouthed about the actual formulation of their steels. According to industry insiders, these steel blends are closely related to or equivalent to a steel known as 440a. By and large 440a steel is formulated for stain and wear resistance rather than holding a high performance edge.
In the kitchen, that’s not a bad tradeoff.
But this compromise in edge performance is compounded by a heat treatment that leaves the steel much softer than it could be. In general, the harder the steel, the keener the edge it will take. However, a hard steel makes it more difficult to get that edge in the first place. So manufacturers leave the steel a little soft, theoretically making sharpening at home easier. If you’ve ever spent an hour or two trying to get a super fine edge on a cheap kitchen knife, you’ll know that there is a big gap between theory and practice.
Upper-end kitchen knives like Henckels, Sabatier, Wusthof, et al., are a little better, but are still softer than they need to be at 52 to 56 on the Rockwell C scale (the Rockwell scale is a scale used to measure the relative hardness of different solids). By contrast, Japanese knives tend to be around 61-62 on the Rockwell scale. Custom knife maker Phil Wilson hardens his S90V (a stainless supersteel) chef’s and filet knives to 62-63 Rockwell.
The next compromise is in the factory edge angles. Most kitchen knives come with an edge that is at least 25 degrees per side, frequently even greater. If you add the two sides together you get a 50 degree included angle. And that’s the best case scenario. Take a look at a protractor if you happen to have one lying around. Fifty degrees is extremely thick. An angle that obtuse is more appropriate for an axe than a chef’s knife. Again, the theory is that the thick angles will allow the edge to resist damage from impaction, rolling and wear better than a thin edge. But, as the song says, it ain’t necessarily so.
Finally, there is just plain cruelty and misuse. While I’m certain none of you would ever use the sharpener on the back of an electric can opener, or use a glass cutting board, or store your knives loose in a drawer or put them in the dishwasher, it does happen. And when you add soft steel and thick angles to the general abuse that knives see in the kitchen, you end up with tools that are more adapted for bludgeoning oxen than fine dicing a soft tomato.
Take heart. The news isn’t all bad. We can fix these problems. Geometry is far more important than steel. With some basic knowledge and the willingness to invest a little time, you can realistically expect a dramatic increase in knife performance.
First, do no harm: General knife care
- Use wooden or composite plastic cutting boards only. Glass, ceramic, marble and steel will cause the edge to roll or chip. Bad. Don’t do it.
- Don’t drop your knives in the sink. Not only is it a hazard to the person washing dishes, but you can also blunt the tip or edge.
- Don’t put your knives in the dishwasher. The heat may damage wooden handles and the edges may bang against other cutlery or plates.
- Keep your knives clean and dry. Sanitize if necessary.
- Do not store your knives loose in a drawer. Use a block, magnetic strip, slotted hanger or edge guards. The magnetic strip is not recommended if you have children or inquisitive pets.
- Finally, your knife is not a can opener, a screwdriver, a pry bar, box cutter or hammer. There’s a special place in Hell reserved for people who abuse their knives this way.
If your knives won’t fit in a block, simple plastic blade guards are a good solution
Second: Modify for performance
This is the easy part. Establishing and maintaining high performance edges is what this tutorial is all about. It can be as simple as steeling with the proper technique or as complex as creating specific edge bevel and edge aggression strategies for each knife in your collection. It’s all up to you.
While you can’t change the steel your knife is made from, you can certainly keep your knives at peak performance – and without too much difficulty. We’ll discuss high performance edges and sharpening strategies a little later in the tutorial.
Third: Modify for comfort
This is something very few chefs (and even relatively few knife makers) take into consideration. Ask any chef to show you his knife-hand calluses. He’ll have a thick one at the base of his first finger from the “pinch grip” used in most kitchens. He or she may also have another on the side of the second finger where the finger rubs against the bolster or dropped portion of the blade that extends below the handle.
He will also have aching hands and possible repetitive stress injuries.
In the interest of economy, most knife manufacturers leave the spines of their knives squared off. The edges of the spine can sometimes be sharper than the knife itself. That edge cutting into your finger can lead to blisters, calluses, reduced circulation, numbness and injury.
If you ever handle a chef’s knife made by Canadian knife maker George Tichbourne you’ll know that it doesn’t have to be that way. Tichbourne worked with several professional chefs when designing his kitchen knife series. One of the key features is a smoothly rounded spine. It doesn’t abrade your finger, cut off the circulation, make your hands numb or create any of the other discomforts associated with standard kitchen knives.
You can do the same in less than half an hour. Lock your knife, edge down, into a padded vise. The padding doesn’t have to be anything elaborate. Two pieces of flat rubber or leather will keep the jaws from scratching the blade. You’ll need a sheet of fine (600 grit) wet/dry sandpaper available at any auto supply store or an abrasive cloth, sometimes called a crocus cloth. Using a gentle shoeshine motion, lightly round the edges of the spine. You don’t have to buff hard or remove a lot of metal. All you need to do is break the sharp edge at the base of the spine. How far you take it is up to you. This simple modification will make a world of difference in the comfort of your knives.
Section Two: Steel
An Overview of Steel
By definition, steel is a combination of iron and less than 2 percent carbon. For centuries, carbon was the only alloying element. The problem in the early days of steel making was getting rid of unwanted elements, not adding new ones. However, there are a variety of alloying elements that are added to modern steels to impart various characteristics.
Iron alone is relatively soft. It does not hold an edge well, wears quickly and has little resistance to bending. Add a little bit of carbon and the story changes dramatically. The carbon combines with the iron to form hard carbide platelets cemented together in a matrix of iron. The combination is resistant to wear and bending and will take a keen edge.
Smaller carbides and a tighter grain structure allow for a stronger, sharper edge. Other carbide formers, like vanadium, can refine the grain of the steel further. Knives with a high vanadium content can take a very keen edge, but are harder to sharpen.
Carbon - Present in all steels, it is the most vital hardening element. Greater than 0.5 percent carbon content qualifies a steel as a “high carbon” steel.
Chromium - Added for wear resistance and corrosion resistance. A steel with at least 13 percent chromium is considered “stainless.” Chromium is a carbide former, so it also increases wear resistance.
Manganese - A carbide former. Manganese aids grain structure, increases hardenability, and wear resistance. Manganese is present in most cutlery steels.
Molybdenum - Another carbide former. Increases hardness, prevents brittleness, makes the steel easier to machine.
Nickel - Adds toughness and possibly aids in corrosion resistance.
Phosphorus - Essentially a contaminant.
Silicon - Increases hardness and strength.
Sulfur - Increases machinability but decreases toughness.
Tungsten - Increases heat, wear and shock resistance. Tungsten is the strongest carbide former behind vanadium.
Vanadium - Another carbide former. Contributes to wear resistance and hardenability. Vanadium refines the grain of the steel, which contributes to toughness and allows the blade to take a very sharp edge.
Most kitchen knives fall into the category of “high carbon stainless.” These knives generally contain between 0.5 and 0.8 percent carbon, 13 to 18 percent chromium and a little manganese, molybdenum, silicon, phosphorus and sulphur. This makes for a steel that is easy to produce, is very stain resistant and reasonably wear resistant. Knives from Global and Mac’s Superior line have some vanadium added for improved wear resistance and a finer grain, which allows the knife to be sharpened to an incredible edge.
Carbon Steel versus Stainless Steel
The great debate rages on. Carbon steel advocates claim that their knives take a keener edge, hold it longer and are easier to resharpen than stainless steel knives. Stainless steel users claim that carbon steel knives are unsanitary, leave an off taste in foods and that stainless knives hold an edge longer than their carbon counterparts.
Who’s right? Depends on your definitions and your environment. It’s not as simple as carbon versus stainless.
Carbon steels range from simple iron/carbon combinations to high-alloy tool steels that will cut through concrete without losing their edge. Stainless steels vary from very soft, extremely stain resistant dive knives to super stainless alloys, like Crucible Particle Metals’ S30V, a steel purpose-designed for the custom cutlery industry.
In the far less demanding realm of the kitchen, however, the carbon steel devotees are right. At least until they actually have to use their knives. Then it’s a different story.
Carbon steel kitchen knives generally are a little harder and stronger than stainless steel kitchen knives. They are easy to sharpen and take a screaming edge. And while the patina that develops on a carbon knife can be unsightly (unless you like that sort of thing), it isn’t unsanitary.
But in the wet, acidic environment of the kitchen, stainless rules. For all their faults, compromises and shortcomings, stainless steel kitchen knives work better and will hold their edges longer than carbon steel knives.
Doesn’t make sense, does it?
The culprit is corrosion – the effect of acid and micro-rusting. Even on what appears to be a mirror-bright, razor sharp edge, microscopic particles of rust and corrosion will form, attacking the edge and reducing its performance. Unless carbon steel knives are rinsed and dried frequently, their edges will degrade rapidly in kitchen use. The stainless edge will easily outlast them.
According to chef and knife maker Thomas Haslinger, “Acids of fruit and vegetables are fairly aggressive and will dull a carbon blade more quickly than stainless. The acid actually eats the edge.”
Section Three: Edge Basics
Most kitchen knives are flat ground, meaning that the blade tapers directly from the spine to the edge. Hollow ground, convex ground and saber ground blades are rarely found in the kitchen. I mention them only to confuse you.
Edges come in a variety of flavors. The most common are the V-edge, double beveled edge, chisel ground edge and the convex edge.
V-edges and double beveled edges are variations on a theme. The edge found on your kitchen knives is most likely a V-edge, meaning, oddly enough, that the edge bevels form a V, two surfaces intersecting at a line of (ideally) zero width.
A double bevel takes this idea a little further by adding a second, more acute, angle behind the edge bevel. This secondary bevel is sometimes called a back bevel or relief angle. It’s purpose is to thin the metal behind the edge. The thinner the edge, the greater the cutting ability. However, an edge that is too thin is susceptible to damage. So you add a smaller, more obtuse primary bevel to the very edge to give it the strength to avoid damage from impaction, chipping or rolling.
Chisel ground edges are primarily found on Japanese knives, especially sushi knives. The edge is ground only on one side. The other is side is flat. Hence they come in right and left handed versions. Chisel ground edges can be extremely thin and sharp. If the edge bevel is ground at 25 degrees and the other side is 0 degrees, you have an included angle of 25 degrees – considerably more acute than the average Western knife.
Sometimes known as hamaguri-ba, the convex edge arcs in a rounded curve down to the edge. Thus the final edge is the intersection of two arcs, creating a very sharp edge with more metal behind it than the standard V-edge. Convex edges are generally formed on a slack belt grinder, so they are difficult for the home sharpener to achieve. This can be remedied with the mousepad trick found later in the tutorial. See the Convex Grind FAQ for sharpening methods and a comparison of the convex edge with other edge types.
A double bevel. The wide area is a 10 degree back bevel; the narrow section is the 15 degree primary edge face.
The back bevel also solves one of the great problems with V-edges, the fact that the metal behind the edge gets progressively thicker as the knife is sharpened over time. The knife doesn’t cut as well and becomes harder and harder to sharpen. The answer is to grind the shoulders off the edge at an acute angle, i.e. add a back bevel, then reestablish the primary bevel.
If you sharpen your knife without grinding a relief angle, your edge will thicken over time.
Micro-serrations: True or False?
Knife geeks frequently talk about “micro-serrations,” microscopic teeth on the edge of the knife. Is this really true? In a word, yes. Sharpening by its very nature creates a scratch pattern on the edge of the knife. The coarser the stone, the coarser and deeper the scratch pattern will be and the larger the micro-serrations. Conversely, the finer the stone, the finer and more polished the edge will be with less prominent micro-serrations. The real question is, which one is better?
This is one of the great debates in the knife world – the razor sharp polished edge versus a toothier edge.
John Juranitch in his book “The Razor Edge Book of Sharpening” is emphatic that a polished edge is the answer, that micro-serrations are indicative of a dull knife. His experience comes from sharpening knives for the meat processing industry. Meat cutters go through knives faster than tissues in flu season, so Juranitch’s conclusions are hard to dispute.
However, Joe Talmadge, author of the Bladeforums “Sharpening FAQ;” Cliff Stamp, physicist and knife nut; Leonard Lee, president of Lee Valley Tools and author of “The Complete Guide to Sharpening;” and many others have come to the opposite conclusion: that micro-serrations, in the right context, can be a very good thing.
What is the right context? Later on we’ll examine the difference between push cutting and slicing, their applications in the kitchen and the value of various levels of polish on your knife edges. Which leads us directly to:
The Meaning of Sharpness
What do we mean when we say that we want our knives to be sharp? Seems like a silly question. We all know what sharp is. Or do we?
Sharpness is not just a function of creating a super-thin edge that will readily sever free-hanging nose hairs; it’s also a function of shape and intended purpose. You could grind your chef’s knife to razor thinness, but the edge would crumble the first time you hit a bone or tried to hammer your way through a winter squash. Your knife would be sharp but useless. Similarly, a razor sharp but wedge-thick edge is great on a splitting axe but not much good for carpaccio.
We have to take into consideration the shape of the blade, the angle of the edge bevel and especially the material being cut when we consider how we judge the sharpness of our kitchen knives.
So the real question is not “how sharp should my knife be,” but rather “how do I get maximum performance from my knife under a given set of conditions.” A sharp knife can be defined as one that has a keen edge that can hold up in repeated usage while producing the results we’re looking for in the kitchen.
The Myth of Thick Edges
The theory is that thick edges (larger angles) last longer than thin edges, and the majority of the knife buying public wants the edge to last as long as possible. But it doesn’t work out that way in practice. Thinner edges actually outlast thicker edges almost all the time.
The thinner edge starts out performing better than the thicker edge. So even if it does degrade it has a lot of ground to lose before it falls to the performance level of the thick edge.
Thinner edges cut more easily, putting less stress on the edge. If a thin edge takes three slices to get through a big slab of raw meat, a thicker edge might take six or seven. Or three with a lot more force. The thicker edge is doing twice as much work, degrading twice as quickly.
Thinner edges are easier to control. Lateral stresses are a significant source of edge degradation. The more smoothly, accurately and easily you are able to cut, the less lateral stress you put on the edge.
Thin is good.
A very thin, high performance 10/15 double bevel. The knife is an 8” custom chef’s knife in ATS-34 steel from Steve Mullin.
The High Performance Edge
We want our kitchen knives to cut as easily as possible while maintaining integrity and staying sharp.
For maximum performance, you want the edge as thin as possible. To borrow an image from Joe Talmadge, imagine a woman stepping on your foot. If she’s wearing tennis shoes, it will hurt a lot less than if she’s wearing stiletto heels. The same amount of force applied to a much smaller area penetrates better. A knife edge a thousandth of an inch thick with one pound of pressure behind it concentrates 1,000 pounds of pressure per square inch at the edge. While an actual kitchen knife’s edge will be a little thicker than a thousandth of an inch, the thinner your knife’s edge, the more efficiently it will cut.
To thin a knife’s edge, you lower the edge angle. The problem is that a thin edge is much more susceptible to damage. As the edge becomes thinner, there is less metal to support it. It can roll, indent and chip, causing the edge to degrade quickly.
So the goal is to thin the edge as much as possible, but not so much that it is regularly damaged during hard use. One way to do this is to keep thinning your edge until it reaches an unacceptable level of fragility then back off a couple of degrees. This is easier than it sounds, but not really necessary. We’ll discuss suitable edge angles in just a moment.
One factor that strongly plays into how thin you can take a knife’s edge is the quality of the steel. That’s one of the primary advantages to the new breed of incredibly hard stainless super steels. You can sharpen them to very acute angles without risk of significant damage. As an aside, I’ve taken a chef’s knife made from ATS-34 down to less than 8 degrees per side before it required an unacceptable level of maintenance.
As we’ve discovered, the average kitchen knife is made from pretty mediocre steel. But it can still be much thinner than the factory edge. As a matter of fact you can sharpen your Henckels and Wusthofs to angles that would give the good folks in Solingen the heebie-jeebies without worrying too much.
Section Four: Sharpening Basics
Before we get into sharpening systems and the actual mechanics of sharpening, it helps to understand some of the basic principles. These are the burr, the sharpening angles, the abrasive, consistency and sharpening strategy. They apply no matter what sharpening method you choose.
The Burr
First and most foremost is the burr. The burr is your friend. A burr, or wire edge, is a rough, almost microscopic, raised lip of metal that forms when one edge meets the other. It is the only way to be absolutely certain that you have fully ground an edge. Essentially you grind one side until it meets the other and pushes up a small curl of metal. If you stop sharpening before the burr is formed, your knife will not be as sharp as it could be.
Sometimes you can’t see a burr, but you can always feel it. You check for a burr on the side opposite the edge you have been grinding. Hold the knife blade horizontally and place your fingers or thumb at a 45-degree angle to the edge and pull gently down and away. DO NOT PULL TOWARD THE TIP OR HILT; YOU MAY LOP OFF A FINGER. PULL AWAY FROM THE EDGE. Remember, check the side opposite the one you've been sharpening. You're checking for a very light lip caused by the edge rolling over to the other side. Check at various points along the edge. The burr tends to form quickly at the base of the blade but takes a little longer at the tip. You must feel a burr running all the way from heel to tip to know that you have fully ground that side of the knife.
Hand position for checking a burr.
The Angles
As we’ve discussed, the 50-degree-plus included angle that comes standard on most kitchen knives is way too obtuse. Leonard Lee suggests anywhere from 5 to 20 degrees per side (10 to 40 degrees total) for general kitchen work. Five degrees per side is incredibly thin and would require a very hard, high quality steel to keep that edge in regular use.
For the vast majority of kitchen knives, 15 to 20 degrees per side will provide a significant increase in performance without requiring undue maintenance. Meat cleavers should be a little thicker, say 20 to 25 degrees per side, while dedicated slicers can be taken down to 10 to 15 degrees per side.
The best compromise in the kitchen has proven to be a 15/20 double bevel. That is a 15 degree back bevel with a 20 degree primary edge face.
A 15/20 double bevel illustrated. This is an excellent performer in the kitchen.
Abrasives
You sharpen your knives by scraping away metal. That’s really all there is too it. But there is a huge array of abrasives available.
Traditionalists will demand an Arkansas stone. These stones were originally mined from a novaculite deposit in Arkansas. They were graded, from softest to hardest, as Washita, Soft Arkansas, Hard Arkansas and Black Hard Arkansas. However, the best parts of the deposit were mined long ago, leading to spotty quality in the natural stones. They have since been replaced by ground novaculite reconstituted into benchstones. These can be found under the Arkansas Perfect name.
Synthetic aluminum oxide stones are very, very hard and don’t wear like natural stones. They clean up easily with a scouring pad and are more consistent in their grading systems. Spyderco and Lansky both manufacture synthetic stones in a variety of grits (see discussion of grits below).
Japanese waterstones are considered by many to be the ultimate sharpening tools. Although natural waterstones are extremely expensive and hard to find, reconstituted stones are readily available. These reconstituted Japanese stones are held together by a resin bond, cut very quickly (and wear more quickly as well) and are available in extremely fine grits that will put a high polish on an edge.
Synthetic waterstones, as used by EdgePro systems, are formulated from aluminum oxide specifically for knife sharpening. Like Japanese waterstones, they need to be wet in order to cut effectively.
Diamond “stones” have man-made diamond particles imbedded in or coated on a base metal. They cut very aggressively and should be used with caution. They were formerly available only in very coarse grits, but that is changing rapidly. According to Leonard Lee, monocrystalline diamonds are preferable to polycrystalline diamonds in a diamond stone. They are nearly twice as expensive, but last much longer. EZE-Lap, Lansky and DMT make excellent diamond stones.
There are two other issues related to abrasives that must be considered: grits and lubrication.
You Want Grits with That?
All of these abrasives come in a variety of grits from very coarse to ultra-fine. Grit refers to the size of the individual particles of abrasive in the sharpening stone. A stone with a finer grit has smaller particles, and produces an more polished edge with less prominent micro-serrations. A stone with a coarser grit has larger particles, produces an edge with more prominent micro-serrations, and tends to abrade metal away more quickly. There are several different grit rating systems, and unfortunately it is very difficult to correlate these different systems. For example, Japanese waterstones are graded differently than diamond stones and both have different numbering systems than the codes found on powered grindstones. Steve Bottorff, author of “Sharpening Made Easy” has taken a stab at it here if you’re interested.
What we do know is that you’ll need a coarse to medium stone for shaping the edge and removing the shoulders of over-thick edges. You’ll also need a fine stone for sharpening the final edge. The combination stones found in most hardware stores just won’t do the trick. The coarse side isn’t coarse enough and the fine side isn’t fine enough. Any of the sharpening systems mentioned later will come with appropriate stones.
In very general and imprecise terms, stones rated lower than 300 grit are coarse, 300-400 are medium, 600+ are fine and 1200 and up are extra fine.
Japanese waterstones have their own grit rating system. They cut so quickly that anything below 800x can be considered coarse, although they’ll leave a much more polished edge than a corresponding Western stone. 1000x and 1200x can be considered medium and medium-fine and make an excellent general purpose stones. Waterstones can go up to 8000x, but that’s really overkill for kitchen purposes.
The stones that come with Spyderco’s Sharpmaker are listed as fine (the white stones) and medium (the grey stones). The grey has been compared to an approximately 800x waterstone, the white to a 1200x waterstone in effect.
The synthetic waterstones from EdgePro systems also have an idiosyncratic rating system. The coarse stone is listed as 100, the medium as 180, the fine 220, extra fine 320, ultra fine is 600. However a conversation with Ben Dale, owner of EdgePro, revealed that the extra fine stone is equivalent to a 1200x Japanese waterstone and the ultra fine equivalent to a 2000x Japanese stone. The basic system comes with a medium and fine stone, which should be sufficient for most needs, though the coarse stone comes in handy for quickly reshaping bevels.
Oil or Water?
Everyone knows you need to lubricate your sharpening stone with water or oil, right? So the question is which one is better. Neither. The purpose of a sharpening stone is to grind the edge and remove metal. Oil reduces friction and makes the process much slower.
Supposedly oil helps float away metal particles that would otherwise clog the pores of the stone. You can do the same thing by wiping the stone with a damp cloth when you’re done. Steve Bottorff reports that you can clean your Arkansas stones with paint thinner. Synthetic stones clean up with a scouring pad and abrasive cleanser.
According to Joe Talmadge, if you have already used oil on your Arkansas stone, you’ll probably need to keep using oil. But if you have a new Arkansas stone, a diamond stone or a synthetic stone, go ahead and use it without oil or water. It will work much better.
John Juranitch reports that in his company’s work with meat processing plants they discovered that the metal filings suspended in the oil on a stone actually chip and abrade the edge. Although these chips were only visible through a microscope, the meatpackers readily noticed the difference between the knives sharpened on a dry stone and those sharpened on oiled stones.
Waterstones are another matter entirely. Both Japanese and synthetic waterstones require water in order to cut effectively. Japanese waterstones can be damaged if used dry and must be soaked thoroughly before use. Waterstones wear very quickly, revealing new layers of cutting abrasive as the swarf builds up and is washed away. That’s why they are so effective. There is always a new layer of sharp abrasive cutting away at the metal of your edge. By the way, “swarf” is one of those cool terms you get to toss around when you discuss sharpening. Swarf is the slurry of metal filings and stone grit that builds up as you sharpen. Throw that into your next cocktail party conversation and just watch the expressions of awe appear as people realize that you are a sharpening God.
Consistency
You must be able to maintain a consistent angle while you are sharpening. This can be tough to do, which is why there are so many gimmicks and sharpening systems on the market. They don’t provide any magic. All they do is help you keep your edge at the same angle throughout the sharpening session.
Maintaining consistency is a primary reason freehand sharpening with benchstones or waterstones is a little tricky. It takes a lot of experience and practice to keep the edge at a constant angle stroke after stroke using only your hands and eyes.
Sharpening Strategy: Coarse versus Polished Edges
Related to the grit discussion above, the finer the stone you use to sharpen your knife, the more polished your edge will be. And while it can be a lot of fun to create a scary sharp edge that will cut the tops off of arm hair without touching the skin, it’s really not necessary or ideal for kitchen use.
As a matter of fact, leaving the edge of your knife just a little coarse can be a very good thing. This is where we must compare push cutting to slicing.
Push cutting involves parting fibers and requires a polished edge. Shaving, for example, is push cutting. So is peeling an apple or julienning a carrot. You are pressing your thin, finely polished edge through the fibers of the food, pushing them to either side.
Slicing, on the other hand, involves severing fibers and requires a toothier edge. Crusty bread, a soft tomato, roast chicken – anything with an outer layer that is tougher than the squishier inside demands an edge that can bite into the skin without crushing the interior. A highly polished edge will simply skate over the surface of a ripe plum until you put enough pressure on it to push through the skin. But the fruit underneath will give way before that happens. Not pretty.
Now you must decide. Do you do more push cutting or more slicing? Do you have knives that you use more often for dicing, peeling and julienning? Do you have a knife that is dedicated to slicing?
A good basic strategy is to start with a standard 20 degree bevel (a 15/20 double bevel if you’re feeling adventurous) with a moderately polished edge on all your knives. This alone will be a vast improvement over what you might be used to.
Then branch out. If you have a knife that is only used for vegetables, a santoku for example, you can take it to a very fine, highly polished edge. A dedicated slicer can be finished on a medium-fine grit stone, leaving the edge slightly coarse. Your chef’s knife can be somewhere in between.
There is one caveat. The thinner the edge, the finer it will need to be to avoid excessive damage. A coarse edge wears more quickly and requires more maintenance. This is usually not an issue unless you like your edges very thin. Then a polished edge will last longer. Of course if you have a very thin edge it will probably push cut through materials that a thicker edge might have to slice through, so you’re not losing any slicing performance.
If you’re really nuts you can create a dual edge on your knives. This would be a slightly coarse section at the back of the blade near the choil or bolster. The rest of the blade would be finished on a fine or extra fine stone. That gives you a toothy section for cutting through tough materials as you begin your stroke and a finer edge for push cutting through the rest. Yes, this is only for the seriously deranged.
Section Five: Sharpening Step by Step
Hey, 5,000 words into this and we’re actually getting to the “how-to” part.
Okay, here’s where we put all of this together.
Haul out your sharpening rig and let’s grind some metal. Don’t have one yet? Check out the Sharpening Systems section below to see what suits you best.
Got one now? Good.
Remember the basics: burr, angle, abrasive, consistency and strategy. Let’s assume, for the sake of discussion, that you’ve decided to put a 15/20 double bevel on your chef’s knife. Because it’s a general purpose knife, it doesn’t need to have a mirror polished edge. As a matter of fact, a good medium-fine edge is what you’re aiming for. This is your angle and strategy.
Because this is the first time you’ve really tried to change the horrid factory edge, you’ll need to begin with a fast cutting, coarse abrasive. Benchstone, waterstone, Sharpmaker grey stone – doesn’t matter. Start with the coarsest thing you’ve got.
Determine how you’re going to establish consistency. With a Sharpmaker you simply stroke straight up and down. The EdgePro or Lansky rod-type systems have angle guides built in. Freehand sharpening requires a little more skill and patience, but if you use a guide system like the Razor Edge or simply place your thumb on the spine in the same spot every time, you can create a consistent angle.
Advanced Section:
Warning: Math! If you want to be really anal about it, Leonard Lee offers this formula for creating freehand angles of less than 20 degrees. “Use the basic rule that a 1 degree angle subtends an arc of 1 unit at a radius of 60 units. The 1-in-60 rule is close enough for many purposes, particularly sharpening at low angles. You’ll find that a 10-unit rise in 60 units is about 9-1/2 degrees and a 20-unit rise is about 19 degrees.”
This works out to raising the spine 1/8 inch (measured 1.5 inches back from the edge) for every five degrees of angle. The average chef’s knife is about 1.5 inches wide at the heel, so for a 15 degree angle you’d raise the spine 3/8 inch – about the height of six quarters stacked up.
If your knife is wider or narrower than 1.5 inches, measure the height from 1.5 inches back from the edge, otherwise the math doesn’t work. It’s the height/width ratio that gives you the angle.
Forget the math. In a pinch a large binder clip clamped to the spine will get you pretty close.
So, let’s get started:
1) Establish your 15 degree angle. If you’re using a Sharpmaker, put the stones in the 15 degree slots. With a Lansky, Gatco or EdgePro system, slide the rod into the 15 degree setting. With edge guides, clamp the guide at the 3/8” height. Freehanding, raise the spine to 3/8 inch measured 1.5 inches back from the edge.
Now you’re ready to create a burr. Be patient, this might take a while. To grind off the shoulders of the previous edge we’re going to be removing a lot of metal. That’s why we need the coarse stone. At this point it doesn’t really matter what kind of stroke you use. You can go heel to tip or just grind in circles. It doesn’t make any difference.
To keep the aesthetics of the knife, you’ll want the bevels relatively even on each side. If you just grind one side until you get a burr, the other side will require much less grinding. Thus the bevels will be mismatched. To keep them matched, grind one side for about five minutes or so then switch to the other side, maintaining your approximately 15 degree angle. Feel the knife every so often to see if you can feel a burr. Keep grinding and switching sides until you detect a burr beginning to form. Remember, the burr forms on the side opposite from the side you are grinding. If you don’t remember how to check for a burr, see the picture earlier in the tutorial.
As soon as you detect a burr, keep grinding on the current side until the burr runs the entire length of the opposite edge.
If you use the Magic Marker Trick described below, you can save a little time on this step.
2) Repeat on the opposite side until you feel a burr along the full edge of the first side.
3) Optional: If you want to dress up the scratch pattern, switch to your fine stone and give the edge several passes on each side (at the same angle) to polish them out a little.
4) Establish your 20 degree angle. If you’re using a Sharpmaker, switch to the 20 degree slots. With a Lansky, Gatco or EdgePro system, simply change the rod to the 20 degree setting. With edge guides unclamp the guide and slide it forward about an 1/8 to 1/4 inch. Freehanding, raise the spine another 1/8 inch. If you switched to your fine stone, switch back to your coarse stone or the next one up, usually a medium stone.
5) Create a burr again at the new sharpening angle, going back to side one. This time you’re grinding the edges to meet at a 20 degree angle. This will happen very quickly because you’ve already removed most of the metal you need to. The 20 primary edge face will be very narrow compared to the 15 degree back bevel, somewhere around 1/32 to 1/64 of an inch.
6) Switch sides and repeat until you have a burr running the full length of the first side.
7) You’re almost home. Now that you’ve got your burr you need to grind it off completely so that the true edge remains. Now technique matters. No more grinding in circles. Stroke gently from heel to tip, alternating sides with each stroke. Keep the sharpening stone perpendicular to the blade as usual, beginning the stroke at the heel and ending at the tip. Or if you are sharpening on a benchstone, stroke tip to heel, if you’re more comfortable that way. Lighten up on the pressure as you go. There is no hard and fast rule, but five to 10 strokes per side should do it. If your checking reveals that the burr is simply flopping from side to side, lighten up the pressure even more.
8) Change from the coarse or medium stone to the fine stone and continue. Keep stroking side to side until all the scratches from the coarse stone are gone. Continue lightening up on the pressure as you proceed. You are trying to grind the burr off. If you press too hard you’ll simply form another one.
9) Finish with a few very light strokes on the fine stone. Now, to make sure that the burr is completely gone, place the knife on the stone as though you were going to take one last stroke, but this time increase the angle just a hair. On a Sharpmaker, tilt the knife very, very slightly in toward the center to increase the angle. Now guide the knife down the stone using no more pressure than the weight of the knife itself. Switch sides and repeat for one stroke. You can do this for one more stroke per side if you can still feel any vestige of a burr.
If you have a smooth steel or very fine grit ceramic rod you can substitute a couple of strokes per side at a slightly greater than 20 degree angle for this last step (see discussion on steels and steeling below).
Your edge should be frighteningly sharp at this point. If it’s not, you might not have fully ground off the burr. The edge could simply be turned to one side. Try the fine stone and light pressure again. It could also be that rather than grinding off the burr it was simply turned straight down. This will give you an edge that will send shivers down your spine but it will break off in the first use. A light touch at the end of the sharpening process is the key.
If you want your knife too look as good as it performs, progress through the coarse, medium and fine stones at each angle setting while you’re raising your burr. This will remove any deep scratches and give the edge a more refined look.
This edge is not only very sharp, but is relatively strong. With regular steeling it will last for many months, even under hard use. When steeling ceases to have the desired effect it’s time to sharpen again. However, now that you’ve ground the back bevel you really only need to sharpen the 20 degree primary edge. If your knife is very dull go back to step four on the coarse stones. If it is only a little dull you can begin with the fine stones. The burr will be very easy to raise in subsequent sharpening sessions.
Tips and Tricks
There are a couple of tricks that can make the sharpening process even easier. I’ve saved them until the end just to be cruel.
The Magic Marker Trick
One of the easiest ways to ensure that you are matching an existing bevel is to coat the edge with magic marker. As the magic marker is abraded away by the sharpening stone. you will be able to see where the metal is being removed and whether you have matched the angle properly. Once you have coated both bevels with marker, take a swipe or two down your stone. If the marker is wiped off over the width of the bevel you have matched the angle properly. If your angle is too high, only the marker near the very edge will be removed. If your angle is too low only the marker near the shoulder, above the edge, will be removed. Recoating the edge as you sharpen is a good way to ensure that you’re holding the correct angle throughout the process. No matter what type of sharpening system you use, the magic marker trick will save you a lot of time and frustration, especially in matching an unknown angle on one of the guide or rod-style systems.
The magic marker trick also comes in handy when you are establishing a back bevel. If you coat the edge before working at the 15 degree setting you can grind the back bevel until the marker is ground almost to the edge, leaving 1/32 to 1/64 inch. That’s about how wide the primary edge face will be. Rather than grinding all the way to the edge until you get a burr, you can now switch to the 20 degree setting, knowing that the last little bit of edge will become the primary edge face. You still have to raise a burr at 20 degrees, but the marker trick can save you a little time.
The Paper Airplane Trick
Take a piece of paper with square edges. Fold the bottom left corner over until it meets the right edge. Smooth it down. You’ve just turned a 90 degree angle into a 45 degree angle. Fold the creased edge over to the far right edge like you’re making a paper airplane. You’ve just folded it in half again, and you have a 22.5 degree angle. Sound familiar? Twenty-two and a half degrees is pretty dang close to 20 degrees. As close as you can generally hold a specific angle by hand. This folded piece of paper can serve as a guide for steeling your knife, setting an angle on a benchstone or just checking that you’re keeping your angle steady as you sharpen. The paper edge guide is especially handy when you are learning to steel your knives properly. It helps build the right angle into muscle memory so you can do it without the guide when you have a little more experience. Fold the paper again and you have an 11.25 degree guide for steeling those super thin slicing knives that you’ve sharpened to 10 degrees per side.
The Mousepad Trick
Do you have an old mouse pad? Is there an auto supply store nearby? You can make a superb sharpening system for about $5.
Go to your nearest auto supply store and get some 600 grit sandpaper. Mylar-backed wet/dry sandpaper works best. This is the stuff used to sand automotive paint between coats. Get the self-stick kind. If they have higher grits, get a couple of sheets of those, too, 1200 grit is generally the next step up. Go nuts. It’s cheap.
Stick the sandpaper to the mouse pad and trim the edges. This is your new sharpening system. If you have both 600 and 1200 grit, apply one to each side of the mousepad. Make sure you have a work surface you don’t mind scratching up. If you have a double-sided mousepad sharpener, you don’t want to work on your kitchen counter or dining room table. Your spouse will kill you.
This system requires a stropping motion when sharpening, using an edge-trailing stroke. That means that unlike other sharpening methods you don’t lead with the edge, you lead with the spine. Image an old barbershop with the barber stropping his razor, stroking away from the edge. That’s the idea.
To establish your angle, lay the knife flat on the pad, edge toward you. Lift the spine slightly while pulling lightly toward you. Continue lifting until the edge bites into the sandpaper. That’s your stropping angle.
Press down lightly and stroke the knife away from you, spine first, moving from heel to tip. When you reach the end STOP and lift the knife straight up off the sandpaper. Don’t roll it off or lift the spine further or you’ll mess up the edge you’re creating. Turn the knife over and stroke back the other way with the edge away from you, pulling the spine toward you at the same angle as the previous stroke. The really cool thing is that the mouse pad is soft enough that it conforms to the angle of the knife edge. As long as you’re pretty close you’ll be fine. This will give you an amazing edge in a fairly short amount of time. If you want to polish it up, use the higher grit sandpaper on the other side of the mouse pad.
Because the mousepad is soft, it deforms lightly around the edge of the knife and gives you a slightly convex bevel. As we’ve discussed, a convex edge has many advantages but can be difficult to achieve without a belt sander. This is one way to create or maintain a convex edge without serious power tools.
This is the same technique as stropping (below) but with a different abrasive.
Stropping
Stropping is a handy way to finish off a burr or put a final mirror polish on your edge. While you can strop on anything from the back of a legal pad to an old belt, places like Lee Valley Tools and HandAmerican sell hard backed strops. The strop is usually charged with an abrasive, like green chromium oxide paste, so it actually does remove very fine particles of metal.
Like the mousepad trick above, stropping is an edge trailing stroke. Lay your knife flat on the strop with the spine facing away from you. Slowly pull the knife toward you while lifting the spine. When the edge just begins to bite into the leather you have found your angle. Keep that angle as you stroke the spine away from you, pulling the edge along behind. When you get to the end of the stroke STOP. Lift the blade straight up off the strop. Do not lift the edge higher or roll the knife over while it is still on the strop. You can wreck your edge that way.
Now lay the knife flat again, spine toward you, and gently push the edge toward the end of the strop while lifting the spine. When the edge begins to bite you’ve found your angle for the return stroke. This second step isn’t really necessary if you’ve kept your angles consistent during sharpening, but it never hurts to make sure you are holding the right angle. The return stroke is the same motion as the first stroke, simply in reverse. The edge is facing away from you and you pull the spine toward you.
Stropping will create an extremely sharp, highly polished edge optimized for push cutting. To some extent, stropping can make up for less than perfect sharpening technique, especially since it’s a little more forgiving.
Handling Serrated Knives
Serrated knives and bread knives are a special case. Serrated knives will stay sharp longer than plain edged knives, mainly because the insides of the serrations generally don’t contact hard surfaces. That’s what the teeth are for. The teeth not only have a cutting function, but are also sacrificial lambs, offered up to steakhouse swordsman and children everywhere who feel that if they’re not grinding into the ceramic of the plate, they’re not cutting.
There are four ways to sharpen serrated knives:
1) Pretend the serrations don’t exist and sharpen on a stone, sharpening system or electric sharpener as you would a plain edged knife. This will eventually remove the serrations.
2) Sharpen the flat, non-serrated back of the blade. This will sharpen the knife, but also will eventually remove the serrations, though not as quickly as the first method.
3) Sharpen the serrations individually with a tapered diamond or ceramic file.
4) Sharpen on a crock stick setup, going very slowly so the ceramic rod glides in and out of the serrations.
This last method actually works fairly well, especially with the Spyderco Sharpmaker. It’s triangular rods fit into serrations much easier than the standard round crock sticks. If you want to keep your serrated knives as sharp as they can be, the Sharpmaker system is the way to go, though the Lansky rod-guided system also has an accessory hone for sharpening serrated edges.
Chisel Ground Edges
Sharpening chisel-ground or single-bevel knives is not tricky. You simply match the bevel angle and sharpen as usual – but only on the beveled side. When you raise a burr, grind it off by laying the flat side of the knife perfectly flat against your stone and swipe the burr off. It only takes a couple of passes. You can do the same thing with a strop. The back side of the knife must be perfectly flat or you’ll round your edge. All you want to do is grind off the burr.
The back side of a sashimi knife is sometimes lightly hollow ground to make this step easier. You can actually lay the knife flat and sharpen with your usual stroke, edge first across the stone.
How to Tell if Your Knife is Sharp
How do you know when you have achieved the ultimate high performance edge? Depends on what you want to do with it. Remember that we defined sharp not only as two edge faces intersecting at a line of minimum width, but also as a function of blade shape, angle and the material to be cut. We want a keen edge that can hold up in repeated usage while producing the results we’re looking for in the kitchen.
You can tell when you’ve set your knife’s edge bevels correctly by placing the knife at a 30-45 degree angle on your thumbnail and pulling across the edge. A properly set edge will bite in and not slip off your nail. Of course, you could hurt yourself doing this, too. Or, at the very least, wreck your nail polish.
Any slick, slightly rounded surface will do. Take, for example, a plastic pen, stand it at a 30-45 degree angle on a countertop and lay the knife edge straight up and down on the plastic. Pull the edge from heel to tip. If it bites in, you’ve set your edge correctly. If it slides off, you have some more work to do. The sharper the blade, the smaller you can make the angle before it slips.
Another test is to take a Q-tip and push the fuzzy head over the edge. Any nicks or burrs will pull the cotton fibers loose from the head. The Q-tip will also reveal any rough spots in the edge. A well-sharpened edge will feel smooth. This test is more effective for polished edges.
Razor Edge Systems makes an Edge Tester for this very purpose. It is widely used in the meat cutting industry to check edges to see if they need sharpening (or if the meat cutter is just goofing off).
Another check is the “Samurai Hair Test.” Lay the knife nearly flat against the hair on the back of your head and pull gently down. Very gently. An aggressive, keen edge will readily grab the hair. A dull edge will simply slide off. Don’t shave the back of your head. Just pull gently down to see if the edge catches and tugs. I don’t want any irate calls from your barber or hairstylist.
The classic test of sharpening is shaving the hair of your arms. This has several problems, not the least of which is that the hair might not grow back or could come in coarser and darker than the surrounding hair. And if you have a lot of knives to test you’ll end up looking like you have mange.
The real problem with shaving, though, is that shaving is push cutting. A highly polished edge will readily push cut, but, as we’ve discovered, you don’t always want a highly polished edge. A slightly coarse edge that tugs the hair but doesn’t shave will actually slice better than the polished edge. Thus, shaving isn’t the best test for many knives.
There are other opinions on shaving as a test. Cliff Stamp said, “Coarse edges can easily shave, Joe Talmadge was one of the first guys to comment on this. A lot of people think they can't and thus sharpen them pretty sloppily. The more coarse an edge you form, the sloppier you can get and still have decent cutting ability. However you can get better cutting ability but keeping the edge crisp and aligned. This edge will then have a much higher level of push cutting ability, overall durability and edge retention, as well as a slightly higher level of slicing aggression. I have seen edges formed from a 100 grit AO belt that would still shave. This is more coarse than a x-coarse DMT hone.”
Slicing newsprint is a pretty good test. Both highly polished edges and toothier edges (as long as they’re not overly coarse) will readily slice a piece of newspaper held lightly between your fingers.
The best test, though, is actually using the knife for its intended purpose. If you have a slicing knife, try a soft tomato or plum. A keen, toothy edge can bite into the tomato with little or no pressure, just a light draw across the skin. If you have polished your santoku to a mirror-like edge, try dicing a few carrots or potatoes. The reduced effort will be immediately noticeable. And greatly appreciated if you have 50 pounds of beets to get through before service.
A thin, slightly coarse slicing knife will cut a soft tomato with a light pull and nearly no pressure on the blade.
