101: knife sharpening

anatomy of an edge

the tools you need

how sharpening works

the method

 
It makes me sad to think how many pastry-ers out there don’t care for their knives like they should. Admittedly, the pastry crew doesn’t use knives nearly as much as their savory brethren, but that’s no excuse for neglecting your tools! First of all, everyone knows a sharp knife is a safe knife. The easiest way to hack off a finger is when a dull knife slips on product. More than that, I really believe it’s worth the investment to get a nice knife, and if you care for it properly it will last you a lifetime. Soooo, here’s how to sharpen your knife.

Let me say that there are as many methods for sharpening your knife as there are knife owners with a keyboard and an internet connection. So if you hear conflicting information or methods, my best advice to you is to try ‘em all and see what gives you the best results.

Now I’m of the belief that if it’s worth doing, it’s worth overdoing. I’m going to get deep with this topic, so if you have neither the time nor patience for all that, feel free to click on one of the links to jump to the topic of your choice.

One last thing: If you’d like more depth on the art of sharpening, I’d recommend an amazing book by John Juranitch called “The Razor Edge Book of Sharpening.”

anatomy of an edge

I like to be informed. Knowing is half the battle and whatnot. I think it helps to understand how a blade and edge is composed, and what different blade and edge compositions mean for sharpening. Although it might seem like all knifes are basically a triangle of steel with one and sometimes two sharp edges, the truth is that the shape of the blade and angles of the edge mean very different cutting capabilities and methods for sharpening.

How the blade tapers down into a sharp edge is known as the grind of the knife, and there are several different variations out on the market (I’ve left out two varieties – convex and hollow grind – as they aren’t really found in the kitchen knife market and are more for sport, hunting and tactical applications):

flat grind

This is the simplest variety of knife, where the sides of each blade taper down equally from the spine of the knife to the edge, creating a “V” shape. It can be made quite sharp but will not have great durability in the edge because of the overall thinness of material. A true flat grind is pretty uncommon these days, as most knives include a bevel, but traditionally kitchen knives are flat grind knives. This can be a difficult knife to sharpen because a lot of metal has to be removed from the blade, and that’s part of why you don’t find true flat grind knives much anymore.

high flat grind

This is the more common version of the flat grind found in knives today. Although technically the edge has a bevel in it, that bevel is usually pretty slight and found high up on the blade, closer to the spine of the knife than the edge. This allows for more edge retention (stays sharp longer). A variation of the high flat grind is the sabre or scandii grind, where the bevel begins in the middle of the blade instead of near the spine.

compound (double) bevel grind

Again, this grind is what it sounds like, with two different bevels being ground into the blade. The first is similar to a high flat or sabre grind, starting towards the spine, and the second bevel is ground near to the edge. The angle of the edge grind is more obtuse (a wider angle) than that of other grinds, which helps give it durability  and keep it from rolling and chipping as easily, but means it wont create as sharp an edge. When sharpening, two different angles may need to be applied to reset the primary edge and then define the secondary cutting edge.

asymmetrical grind

An asymmetrical grind has a double-sided bevel, but the angle on each side of the blade is different from one another. This is found in higher-end kitchen knives. They create a good balance of sharpness, durability and edge retention. The manufacturer will tell you this difference, and a 70-30 is quite common. It is very important to know whether or not your knife is asymmetrical, and which side is which in order to sharpen it with the appropriate angles and keep the intended profile. I’ve learned that the hard way. Sigh.

chisel grind

Just like a chisel, a knife with a chisel grind has a cutting edge on only one side and will come in left and right-handed varieties. Chisel grinds can be found in high-end Japanese specialty and sushi knives. Most often, the single sided bevel will begin about midway down the blade. A chisel grind gives you a very sharp edge but takes a lot of upkeep. You must be very careful in sharpening a chisel blade so as not to create any bevel on the flat side. Doing so would ruin the effectiveness of the intended grind.

the tools you need

sharpening stones

Your most important tool will be your sharpening stones (also referred to as hones and whetstones). The term “whetstone” would lead to you believe that the stone uses water during sharpening, but actually whet is just an old school term for sharpening. That being said, just about all whetstones use water. Confusing I know. Some stones use oil instead of water (called, you guessed it, oilstones) but I’ve never found oil to be a superior lubricant for sharpening and it makes a hell of a mess.

In reality, sharpening stones made of actual stone are becoming less and less common, with artificial “stones” made of a ceramic like silicon carbide or aluminum oxide being the more popular choice. The advantages of an artificial stone are its cheaper price and the fact that the particle size of the stone is super consistent (and more efficient) and can be modified to cut faster or slower as needed.

Stones run the gamut in price and are found in a wide variety of grits. The lower the number, the more abrasive the grit. An abrasive stone is more porous and takes more material off your blade. The lowest grit stone I have is a #300, and I only bust that sucker out when I have some real nicks to get out or I’ve decided to start cutting stuff with a spoon. Higher grit stones are much finer and made of denser material, meant to buff and polish your blade and refine your edge. At a minimum I’d recommend getting two stones; a #1000 to do the majority of sharpening and a #5000 or #6000 for finish and polish. As an amateur sharpener/knife-wielder, these two stones will serve most if not all of your sharpening needs.

stone fixer

Stone fixer, flattening plate, stone conditioner, nagura stone…all of these are variations on a tool that does essentially the same thing. Over time the surface of your sharpening stone, especially the softer ones, will  take on a concave bevel that can affect the quality of your sharpening. It’s important to avoid this with regular care for the stone by flattening it out. A stone fixer is made of a very rough abrasive that will remove the material from your sharpening stone to level it out. As an added benefit, the stone fixer will grind up powder that can be used for a slurry on the stone before use.

Flattening your sharpening stone is super simple. Draw a rough grid onto the surface of your stone with a pencil.

With even pressure, run the stone fixer over the entire surface of the sharpening stone. The raised areas of the stone will wear away first and show you where the depression in the stone is. Keep running the stone fixer over your sharpening stone using even pressure until all of the pencil marks have been removed. Boom! Your stone is flattened out.

stone base

I highly recommend getting a base to hold and secure your sharpening stones. Some stones will come with a base, but often the stones are sold loose. Without a base your stone will constantly move and shift under your knife while you sharpen, which is a huge pain in the ass. An adjustable base can be nice since it will fit a variety of stones.

sharpening steel

A sharpening or honing steel is a seriously misused and misunderstood tool. I think it starts with the manufacturers that sell mediocre knife sets to big box retailers (we’ve all owned them) and throw the sharpening steel in with the lot. I can’t blame the average consumer for then assuming that the sharpening steel is the sole tool needed to sharpen a knife. But it is not.

In reality, a sharpening steel is used only to redefine your razor edge after your knife has been fully sharpened on a stone. And unless you’re cutting a large amount of protein or tough produce, which might require some passes on a sharpening steel, you really don’t need to use one much at all.

Not only is the intended use of a honing steel misunderstood, the method of use is absolutely decimated by a million and one machismo chefs and cooks whipping their knives back and forth over their steels; on tv, in restaurant show kitchens, and in front of anyone who might be looking. The proper, most efficient technique for utilizing a honing steel requires precision, the lightest touch and a methodical cadence. Not to mention only three or four passes. But that doesn’t look cool, so instead chefs just whip their knives back and forth and the world of sharpening suffers. Regardless, having a honing steel is important. I use a ceramic honing steel, which is more brittle than a metal version but much harder and so gives a better result.

how sharpening works

Ready for this? The stone itself won’t sharpen your knife. A combination of particles from the stone and metal filings from the knife are removed by friction during sharpening and mixed with water on the stone into an abrasive slurry. It’s the slurry that does the work of sharpening your knife. The lesson learned is not to wipe any of that sludge off of your stone or blade as it begins to accumulate during the process. That sludge is good stuff.

I describe two distinct, different methods for sharpening, Western and Japanese (I’ll detail the actual difference below in the method section). Real talk – I don’t know that one method has an advantage over the other. I welcome any backseat sharpening aficionados to weigh in on the subject, but I suspect there are two equal camps that each prefer a style and are still able to cut stuff at the end of the day. I know for a fact that both styles of sharpening can get your knife real f*cking sharp. I actually use both methods – I use the Japenese style initially because it works well at quickly removing a lot of material and I use the Western style when finishing a blade or working on the knife’s tip because it evenly removes material down the entire length of the blade in one stroke.

the method

Soak your stone(s) in water for at least 20min and up to a few hours. The synthetic stone is porous but takes time to fully hydrate. The better hydrated the stone, the farther the water on the stone will get you. Some methods have you soak your stone for up to 24hrs, but I think that’s excessive. Once your stone is soaked, place it on the base and then onto a towel. The towel will help soak up any excess water and grit from sharpening. I also keep a damp towel handy to wipe down my knife between steps.

The photo above shows part of my general setup for sharpening. On the left are the two knives I’m working on. My stone is set in its base and then on a towel to keep water and particles off the table. What isn’t shown is my container of water used to keep the hone wet and a damp towel to wipe off my knife when needed.

Hold your knife by the handle with the edge facing away from you and resting at a slight angle to the stone if you are sharpening in a Western style and perpendicular to the stone if you are sharpening in a Japanese style. I place a few fingers from my other hand on the blade about 2/3 up (a little closer than that in the Japanese style) to apply even pressure throughout the knife’s length while sharpening.

You’ll also want the blade to be raised off of the stone at an angle. That angle is important and really depends on the grind of the blade, but for most knives it will sit around 10-15 degrees. Picture a matchbook under the knife to get an idea of what you’re looking for

western style:

Bring the knife toward you in a smooth motion, maintaining even, moderate-firm pressure and holding the matchbook angle off of the stone. While you draw the knife towards you, run the edge of the blade along the stone from the heel to the tip so the entire edge makes contact.

Without adjusting the angle of the blade, repeat the motion in reverse, pushing the knife away from you and drawing the edge from tip to heel along the stone. This part of the sharpening stroke should be done with slightly less pressure than the first step.

japanese style:

Although much of the process is the same – same 10-15 degree angle off the stone, same back and forth motion – the big difference with the Japanese method is that you will work on one section of the blade at a time, moving up the edge of the blade as you continue a quicker forward and back motion than with the western style.

Using either style or a combination of both repeat the back and forth process until you have removed enough material from one side of the blade that it has pushed metal over to the other side and a burr is created along the edge of the knife facing up towards you. The length of time this will take varies on your technique, your edge and the hardness of the steel of your knife. I typically work each side for anywhere from 5-15min. Check for the burr by gently running your thumb or fingertips from the spine of the blade to the edge (not along the edge itself!), at which point you should feel the rough burr on the side of the blade that wasn’t in contact with the stone. When you feel the burr down the entire length of the edge, you are ready to work on the other side of the blade. If there’s a section of the blade without a burr, work it on the stone until it has one.

Flip the knife over, burr side of the blade touching the stone at the same matchbook angle. Repeat the sharpening stroke you used to create the burr. It should take about as many strokes to even the burr as it took to create it, or about the same amount of time if you don’t feel like sitting there counting knife strokes. You may need to flip the knife back and forth a few times, with just a few strokes on each side to even the burr out and move on.

Grab a finer grit (higher number) stone and repeat the entire process. It’s this step that I start a slower pace using the Western method. I usually work the stone for 10-15min to get a strong polish on the edge.

Your last step will be giving your knife a few passes on your sharpening steel. The angle of the blade off of the steel will be the same as when sharpening on a stone in the Western style. Draw the knife down the steel, using as little pressure as possible – ideally just the weight of the knife sitting on the steel.

You’re all set! I use my knives a lot but not on material that wears an edge quickly, so I give them the full sharpening regimen maybe twice a month. There’s no set standard of how often you should sharpen yours, just use common sense to judge when they could use a tune up.

Happy cutting!
Chef Scott