Cooking

A beginner’s guide to sharpening knives

A few months ago, I decided to buy a set of whetstones to sharpen my knives. The decision to do this came from the breaking down of my sharpening tool and the fact that my knives were getting dull. I had one of these twin diamond or ceramic roller things that work reasonably well and got the job done quickly enough. After this thingamabob broke down, I thought it was time to get serious about sharpening knives.

My main usage of knives is in the kitchen, much like most people, I imagine. Being able to reliably and effortlessly cut whatever needs to be cut is simply wonderful. Not just that, it’s actually safer to cut with a sharp knife, given proper handling. The most dangerous accidents in the kitchen happen with dull knives. When a knife doesn’t cut properly, you have to use more force. If the knife then slips away uncontrollably, that’s when things go wrong. A sharp knife is a joy, and being able to sharpen a knife is a joy forever.

A while ago Brad Leone of Bon Appetit’s YouTube channel came out with a video on sharpening knives with whetstones. Perfect, I thought, I’ll get a set of stones and start sharpening. He uses the Bob Kramer stones and technique, which I’ll describe in a minute. In my first attempts, I tried to mimic the technique, but I couldn’t make it work. Patiently, I started to search the internet for advice and videos on sharpening knives. I found quite a lot, and it seems there are many different styles and techniques out there. So this is a guide for beginners written by a beginner.

I’ll just catalogue the various styles and techniques I’ve found and I’ll give my honest opinion about them. The most useful information, I think, is in the form of YouTube videos when it comes to such a practical skill, so I’ll link to the videos or channels I used.

True grit

Whetstone knife sharpening is done using stones of various grit. The grit indicates abrasive action, as metal is actually ground away from the blade in the sharpening process. The grit is measured in a very strange unit that seems to have no technical definition, but higher grits correspond roughly to smaller particles (no pun intended). A grit under 500 is fairly coarse, something that’ll feel rough on your fingers. Something in between 500 and 3000 is a medium grit, which will already feel fairly smooth but grippy to touch. Upwards of 3000 would be a fine grit, and this will feel absolutely smooth. Each grit has it’s own application. Coarse grits are used for shaping, while fine grits are used for polishing. It is possible to do coarse grit work on finer grits, but it will just take a lot longer.

Typically, a basic setup uses two stones, one medium and one fine. The medium stone is used to establish an edge, while the fine stone is used for honing and polishing. Most kitchen knives will not require massive overhaul or regrinding of the edge, so there’s limited usage of the coarse stones in practice. A minimal setup would be a single medium grit stone, which is versatile enough to do all sorts of work, say 1000 grit. Grinding a new edge on medium grit doesn’t take forever, and by varying pressure, it can produce a functional burr-free edge. If you do it right, this will be much sharper than how most knives in a cooking shop.

The brand of stone is, from what I can tell, mostly about personal preference. Some people are very happy with King, others with Naniwa. Most people do seem to agree that Japanese whetstones are the best. Murry Carter (more about him later) points out that the abrasive doesn’t really matter, provided you use a proper technique. He demonstrates that you can get a knife sharp using a cinder block and a piece of cardboard. I bought a set by a brand called Skerper, which I cannot find anywhere but the website I bought them from. I have a creeping suspicion that they’re simply a cheaper repackaging of Naniwa. Anyway, they’re Japanese made, seem to work well and they’re affordable, which is perfect for a beginner like myself.

One thing to pay attention to is how to apply water to your stones. Some stones are splash-and-go, while others need to soak. The splash-and-go tend to be more expensive, of course. Their advantage is not overwhelming, as most people will sharpen over their sink anyway, and the soaking takes only a couple of minutes. When I break out my stones, I simply make sure to soak them first before everything else, such as wetting a cloth, preparing the stone holder and gathering the knives I want to sharpen. By the time I’m ready for the actual grinding, the stones are sufficiently soaked.

Finally, a stropping leather is a fine addition to any set, as it can give that nice finishing touch by getting a super smooth polished edge. It can also be used for daily knife maintenance, as shown by YouTuber Burrfection. For completion, I purchased a Zwilling stropping leather block.

Additional equipment you might consider using are flattening and dressing stones. A dressing stone is used to clean out metal particles from especially finer stones. Flattening stones are ideally avoided altogether by using the full length of the stone, or otherwise grinding the knife in the spots where the stone is not flat. When you grind steel on a whetstone, you don’t just remove steel, you also grind down the stone.

Getting the angle

One of the most important things about sharpening a knife is getting the angle right. This is by far the trickiest part that requires the most practice. There are various tricks and helps, such as using a book of matches suggested by none other than Bob Kramer himself. There are also little wedges you can buy to help establish that angle. Getting a consistent angle all across the edge of the blade is the key to obtaining a nice sharp knife. What works for me is to grip the handle while having my index finger on the blade. Other techniques might work for you. I’ve noticed, for instance, that Bob Kramer has his hand on the handle while holding the blade between his thumb and index finger.

For chef’s knives, the general advice seems to be and angle of 12 to 18 degrees with the stone. Murray Carter advises to grind at a bit of a shallower angle than what you’re aiming for on the edge, since you’ll always waver a bit. A shallower angle makes sure you don’t waver outside the intended range. When it comes to choosing what angle to use, I think in this case Murray Carter’s advice is pretty solid here too: angle is a matter of experience and usage, if you use your survival knife to chop down trees like Bear Grylls, you might wanna grind in a shallow angle, while your precious sushi knife could probably use a very acute angle. A more acute angle leads to a sharper knife, but it’ll also dull quicker.

Techniques

There are two elements used by all knife sharpening techniques described here: edge-leading and edge-trailing strokes. The two strokes are called such because they define the direction of motion. In edge-trailing strokes, the knife moves in the direction of the spine across the stone and the edge trails. In edge-leading strokes, the knife moves in the direction of the edge, such that the edge leads. Both can typically be used on a whetstone. However, only edge-trailing strokes can be used on a stropping leather, otherwise the knife cuts into the leather.

I tried the Brad Leone/Bob Kramer method first, which didn’t really work for me. When I wasn’t cutting into the fine grit stone with the edge-leading strokes, I was dulling the edge I carefully built up on the coarse stones. Then I tried the method I describe below as successively raising a burr, which gave me okayish results. Finally, I settled on Murray Carter’s technique, which saw me getting razor-sharp edges on every knife I sharpened. However, what works for me may not work for you, so I invite you to try all of them, or anything else that’s out there.

Successively raising a burr

As far as I’ve seen, the most commonly suggested technique is what I call “successively raising a burr.” A burr or a wire-edge forms when some very thing metal at the edge clings on. If you’d take a perfectly honed edge and zoom in with a microscope, it’ll look more or less like the sketch on the left: a perfect triangle. If you’d then grind this edge on a whetstone, a burr will form on the other side, which is what I’ve tried to sketch this on the right.

Dean O has an excellent video on how to detect such a burr. A burr raised on a coarse or medium stone will be quite pronounced if you’d graze it with your fingertips or nails, but he shows several other methods as well. Also, for some amazing electron microscopy pictures of burrs and other sharpness-related concepts, check out the science of sharp.

The technique starts with grinding both sides of the blade evenly until you can feel a burr all the way across one side of the edge. One video I’ve found very instructive is Peter Nowlan’s. He uses a single 1000 grit stone and explains how lighter and lighter pressures form smaller and smaller burrs. Nowlan also emphasises that it’s generally important to only apply pressure on the edge-trailing strokes, as you might cut into your stone. I can tell you that especially fine grit stones are amenable to this. Nowlan’s channel is full of instructional videos on knife sharpening and I highly recommend them.

After the lightest pressure is used, generally you would use edge-trailing strokes only. If you have a fine stone, this is the point where you want to switch to it. The finer stone will polish the edge, ensuring a smooth cut. Some people, for instance Cook with E, will tell you that you need to use the same number of strokes on both sides, decreasing the number until you finally hit one stroke on each side. I’m not convinced it’s necessary, but it seems like good practice anyway.

Successively finer grits

This is Bob Kramer’s technique, also favoured by Brad Leone in the aforementioned video. The basic method consists of both edge-trailing and edge-leading strokes in succession, simply stroking up and down the stone. Constant pressure is applied to both strokes, it seems, though this is not entirely clear to me.

The technique proceeds by starting on a coarse stone and grinding until a burr forms, after which the stone is switched for a finer grit one, using finer and finer grits until you reach your finest grit stone. Brad Leone mentions that the movement and pressure don’t change, but because of the finer grit, you start removing less material and end up with a polished edge. Microscopically, what happens is very similar to the previous technique of successively raising a burr, but the means by which successively smaller burrs are formed differ. Brad additionally finishes his knife on a leather strop using edge-trailing strokes.

Murray Carter’s technique

In my opinion, the best instructional video on knife sharpening out there is Murray Carter’s almost 3-hour video on knife sharpening fundamentals. It is very detailed, using many example knives. He shows how to deal with a curved blades, how to grind a new point, how different types of steel are sharpened, you name it. He describes a 7-step process that also includes properly cleaning and inspecting the knife. He distinguishes a primary and secondary edge, pointing out both need maintenance.

Key to his technique is a simple test he calls the “three-finger test of sharpness.” This basic test is what really allowed me to get that razor-sharp edge. It sounds simple, but just like sharpening itself, it’s a skill and it takes practice. You take the knife in your dominant hand and flip it edge up, then you take your thumb on your other hand and place it on the spine, while you put index, middle and ring finger on the edge. Carter emphasises, and I want to repeat it: the thumb is extremely important, it’s your anchor, it allows you to control the pressure you apply with your fingers. The test consists of sliding, very carefully, your fingers along the edge. It being a skill, it’s useful to practice as much as possible on as many knives as possible. Now, whenever I see a knife, I pick it up and administer the three-finger test. Most knives I encounter, unsurprisingly, are rather blunt: if you can apply some pressure and slide without cutting into your skin, the knife is dull.

The initial grinding is the same as with successively raising a burr: both edge-leading and edge-trailing are employed, stroking the knife up and down the stone. Significant pressure is only applied on the edge-trailing strokes. Carter advises beginners to stop frequently to observe the knife, both visually and using the three-finger test. The amazing thing is that you can actually see and feel the edge getting sharper. As the edge gets sharper, you’ll be able to apply less pressure in the three-finger test. When the edge is sharp, you can only apply very little – hardly any – pressure. Any bit of pressure and the knife will cut right into your skin. If you’re using a coarse or medium grit stone, the edge will be pretty rough, and the edge will actually grip your fingers when you try to slide them. This is the point where you’ve established a primary edge.

Once you detect a sharp primary edge all the way along the blade, you’ll switch to exclusively edge-trailing strokes. Edge-trailing strokes tend to preserve the edge better. Additionally, any burr that’s formed will be on the edge and gradually ground off or otherwise easy to remove. Finally, you can switch to that fine grit stone to polish the edge to a nice mirror finish. Again, using only edge-trailing strokes and a stropping motion. Carter removes any burr that’s still left by cutting into a piece of soft wood. The leather can be used as a finishing touch.

I recommend any prospective knife sharpener to check out his almost 3-hour video. It’s entertaining, it’s relaxing, it’s educative, it’s a must-see. This particular video was actually a DVD he shot some time ago, but recently decided to put on YouTube for free. Thanks, Murray!

Tips and tricks

I’ve found various tips and tricks online. I have to admit right away that I didn’t use any of them. After I’ve found Murray Carter’s method, I didn’t feel like I needed them. But again, what works for me may not work for you.

Some people recommend marking the edge with a sharpie or magic marker. The ink is ground away with the metal and so you can see exactly where you’ve removed material. This is especially useful if you have problems controlling the angle. I personally don’t see the need, because I could see it equally well without the sharpie. Especially on coarser stones, you can clearly see where the stone has scratched the metal. But initially it may provide some support for those who need it.

Peter Nowlan recommends sticking some tape to the blade if you don’t feel confident about your angle. This is done to avoid scratching the blade. This may be good for some people who want to preserve the look of their expensive blade. Personally, I don’t mind any scratches, really. Besides, if you have a nice fine grit stone, you can polish those out in no time. It’s probably most useful for people who want to start with a single stone.

Sharpness tests

There are various sharpness tests you’ll come across and when performed properly they’re very helpful. Aside from the aforementioned three-finger test, you can use these tests to determine if your knife is sufficiently sharp. They’re also useful to learn the three-finger test, as they can help you distinguish sharp from dull blades. Whatever test you use, make sure that the blade is sharp all along the length of the edge.

Something you’ll see a lot is shaving some hair off your arm. Be careful when you do it though, especially when testing the tip. If the knife isn’t shaving, but you think it’s sharp, try varying the angle at which you shave. Don’t increase the pressure on your skin!

Murray Carter proposes a tomato as an additional sharpness test, alongside the three-finger test of course. If the knife is sharp, it will slide cut the tomato skin with the lightest touch. Ideally only under the weight of the knife itself. If the knife is dull, it will slip off sideways.

Cutting paper, especially newspaper, is another good test. Actually, there are several tests that involve cutting paper. I’ll point out the various ways in which you can test your knife using paper.

First off, simply slide cutting paper. However, if you do this, do it properly. I’ve seen some people who positively rip through a piece of paper as fast as they can and proclaim the sharpness of the knife. No, a sharp knife will cut through paper using very light pressure and at very slow speeds.

Second, a sharp knife can cut very thin strips of paper. The slower you can cut thin strips with almost no pressure, the sharper the knife. A wider piece of paper can withstand more force before it buckles, which only happens if the knife is dull. Thin strips therefore means the knife cuts with very little force.

Thirdly, you can try is to push-cut paper, meaning the knife cuts paper without any sawing or. Again, a sharp knife can move through the paper slowly and without effort.

Finally, paper can reveal how well you’ve polished the edge. A sharp knife with a nicely polished edge will cut through paper smoothly all the way. If you feel any hiccups or snags as you slide-cut, or you feel more resistance somewhere, check your polish there.

It’s important to note that these various tests have their own accuracy, as it were. For instance, a knife can feel relatively dull in the three-finger test but still cut paper. This is simply because a knife doesn’t actually need to be razor-sharp to cut paper. However, there are also more complicated cases. Carter, for instance, demonstrates a knife that shaves but can’t cut a tomato skin. Personally, I think the three-finger test is the most accurate one, and so I definitely consider it an essential skill for any knife sharpener.

Finishing up

If you’re a prospective knife sharpener, I recommend getting a 1000 grit stone and a fine grit stone, say 5000 or 6000. Don’t worry too much about the brand, you can always replace them later. In fact, they wear, so you’ll have to replace them eventually. It is possible to start out using only a 1000 grit stone if you wanna go budget.

Other than that, I’d say watch as many videos as you can. Humans have special neurons called mirror neurons, which can simulate behaviour observed from others. Seeing someone do something is therefore much more informative, especially when the skill to be learned is practical, like knife sharpening. If you’ve read this article, you may still have no idea how to hold your hands or position the stone. If you watch a couple of the videos I’ve linked, you’ll immediately have a quite distinct idea how to hold the knife, how to position the stone, and how to grind. Besides from that, your mirror neurons will be “practising” those movements, preparing your body for when you’re actually going to perform them.

That said though, it’s probably a good idea to start with knives that you can afford to ruin. Don’t start on your favourite thousand-dollar custom made Japanese sushi knife. On the other hand, don’t start on a budget knife from your local supermarket either. Use some decent steel.

Whatever you do, don’t lose hope and don’t lose patience. It’s a skill, it takes practice. In the beginning, it can take a long time to establish that edge properly. Don’t give up, keep going. I’ve found it quite meditative and relaxing, splashing some water and grinding away. The first time I successfully got a sharp edge, it took me over two hours. But after a bit of practice, anyone can do it quick enough. Within no time, you too can get a knife razor-sharp within 15 minutes.

Happy sharpening!

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