Knife Sharpening Guide – How to Sharpen Kitchen Knives
If you want to kickstart your sharpening interest seriously, we highly recommend our sharpening courses in Bromma. Our stone sharpening courses have become very popular, and many have described the course as a quick and easy way to get into sharpening correctly. After the course, you will possess the necessary knowledge, and with a little practice at home, you will quickly become a confident sharpener. No prior knowledge is required, and we guarantee that you will leave the course with a razor-sharp knife and newfound knowledge in knife sharpening.
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Starting to sharpen on your own
Sharpening your kitchen knives yourself is fun and rewarding. The feeling when the knife glides easily through a tomato without turning the ingredient into a pulpy mess can only be surpassed by the knowledge that you yourself sharpened the blade. In our opinion, it's the most enjoyable and useful hobby you can get into. But how do you start? What do you need? What's the most important thing to consider? Our advice is to start by making sure you have the following:
1. Curiosity. If you're reading this, you probably have enough.
2. A little patience. Like everything else worth doing, becoming a skilled knife sharpener takes time, and you'll hit some rough patches along the way. But don't despair! If you follow a few simple tips, your knives will be razor-sharp on your very first try.
3. A coarse diamond sharpening stone, approximately 150 grit. (For worn knives and to keep the stones flat)
4. A medium-fine wet stone, approximately 1000-2000 grit. (For everyday sharpening)
5. A flat, fine wet stone, approximately 3000-4000 grit. (For polishing the edge. Can be omitted if a utility edge is sufficient)
6. A sharpening stone holder. (Convenient to have, but you can manage without it)
To understand the choice, you need to know the basics of knife sharpening. Essentially, it's about creating a sharp edge by removing metal from the blade in a controlled manner. If we look at the knife's edge, it resembles the letter V. The tip of the V-shape at the bottom is the actual edge. And it is from the sides of the V-shape that we grind away material to create the edge. Coarser stones remove more material, but also leave deeper scratches. Finer stones leave fewer scratches and form a smoother edge, but they also remove much less material. Therefore, generally for each sharpening, the rule is to first use as coarse a stone as needed to shape the edge, and then progressively finer ones to smooth it.
Your First Sharpening
If the edge has visible/palpable nicks, or is simply very dull, start with the coarsest sharpening stone. If the knife is already reasonably sharp and the edge is undamaged, start with the medium-fine stone.
To shape the edge, you draw it at a fixed and steady angle and with light and steady pressure back and forth along the wet sharpening stone. Imagine that it's the side of the V-shape that's being drawn against the stone's surface. A lot can be said about the angle of the V-shape, but for the first sharpening, let's say we choose approximately 10-15°. You get roughly that angle if you lay the knife flat with the blade against the stone and the edge facing you, then angle the knife spine up until you can just fit your little finger under it.
To achieve even pressure, hold the fingers of your other hand against the blade near the edge. You don't need to press hard at all. Make sure the stone is wet and draw the knife up and down repeatedly in this manner. The difficult part here is to maintain a steady sharpening angle, as well as to maintain even and appropriate pressure. There's only one way to learn this: Practice, practice, practice.
Since you can only apply pressure to part of the knife blade, you sharpen it in segments. A segment is complete when you have removed enough material to reach the tip of the V-shape. To check that you have done this, you can feel with your fingers for a small burr along the edge on what is the top side when you are sharpening. A burr consists of metal shavings that have been pushed over the edge. Make about ten strokes up and down, then feel for the burr. Repeat until you feel the burr. Important: If you don't feel a burr, you are not done.
One side is complete when you feel this burr along the entire knife blade. Before you have mastered knife sharpening, you may find that some parts of the blade are a little more difficult than others. Be patient here. We repeat: As long as you don't feel a burr along the entire blade, you are not done.
But when you do, you are done, and then it's time for the other side. If you are reasonably steady with your "other" hand, you then switch the knife and repeat in reverse. If it feels awkward, you can instead turn the spine of the knife towards you and the edge away from you and keep the same hands for holding the knife and applying a little pressure. Please study sharpening video number 2 above to see a good example of this technique.
When you have a burr along the entire other side of the blade, you can remove some of it by drawing that side against the stone with only upward movements and with less pressure than during the sharpening itself. Now you are done with the initial sharpening and have formed the edge. Reward yourself with a pat on the back. Just remember that your fingers are probably completely black from the metal material that you have so diligently sharpened off the knife blade.
Now it's time to change stone to the next grit and repeat. When you use the fine whetstone, it's quite difficult to feel that little burr, but it's not as important at this stage because the edge is already formed. Here it's about straightening the edge and removing burrs rather than creating new ones.
When you are done with the finest stone, you are done with the sharpening. Give yourself a huge congratulations and get out the cutting board and tomatoes, apples, bell peppers, onions, and whatever else you have in the fridge and celebrate by slicing and dicing to your heart's content.
In-depth look at the range of whetstones
A Japanese whetstone sharpens by means of the stone's sharp particles abrading the steel. In Shapton's case, these particles consist of aluminum oxide, which becomes dulled and rotates out of the stone. This forms a slurry together with the knife's steel residue. A whetstone can be more or less effective depending on the abrasive particles it contains, the binder that holds the stone together, and the hardness of the steel to be sharpened. We will now go through the different types of stones that can be used. This is a rather long text, but we believe it will give you a good understanding of what you want to achieve and how to get there. Take your time, it's worth it.
Diamond stone.
This is a rough beast. The diamond stones used for knife sharpening consist of thousands of industrial diamonds bonded to a metal plate with nickel plating. There's a whole range on the market, from #100, which is the coarsest, to #1000, which is very fine in this context. We at Cleancut believe that only coarse diamond plates are suitable for kitchen knives. The wear and tear on fine-grained stones is simply so great that the stone's lifespan becomes short. We therefore focus solely on the really coarse stones, #150, and these are used both for sharpening and repairing knives and for flattening regular whetstones.
Flattening a whetstone is very important. You do it for two reasons. Firstly, the stone needs to be completely flat to ensure a correct contact surface. When the stone is used, it will always wear more in the middle than around the edges. This gives the stone a concave shape, similar to a skateboard ramp. If you sharpen on a concave stone, the stone will create different angles depending on where on the stone you are. Therefore, it doesn't matter if you, as the sharpener, hold the knife at a constant angle; the result will suffer. The second reason you want to flatten your stone every time you've sharpened is to clean the stone of steel residue. Perhaps you've noticed that your stone gets darker after a while and has black streaks on it? That's steel residue from the knife that forms a layer between the stone and the knife. The steel residue clogs the stone and covers the sharp particles in the stone that are essential for the stone to "cut" effectively. You get an increasingly inefficient stone, and again, the result suffers. A flat and clean stone is the key to fast and effective stone sharpening, and a coarse diamond stone is the most effective way to level your stones.
The diamond stone is also the most effective way to rough-sharpen a knife. You can use it for several different tasks. The most obvious is to grind away nicks and broken tips. Here it is used like a regular sharpening stone, and once you have ground away enough steel, you switch to a finer-grained whetstone. Maybe your knife doesn't have any nicks but is very worn on the edge? We then usually say that the edge is rounded and has an edge that resembles a U more than a V. Here you need to grind away the "shoulders" of the edge so that the U-shape transitions to a V. Here too, the diamond stone is a good tool as it saves time compared to a whetstone. The last area where a diamond stone is invaluable is if you want to thin the blade sides of a knife. If you take out your knife and pinch the edge with your thumb and forefinger, you want that area (the bottom centimeter) to be thin and fine. If you instead have perceptible mass there, the knife will cut significantly better after thinning. A good diamond stone does that job faster than a 220 grit whetstone, but will simultaneously leave coarse marks and scratches that you need to grind away with a finer stone (preferably with a whetstone between 220-500 grit). So you have to choose between either using the fast diamond stone that leaves scratches, or spending more time with a coarse-grained whetstone.
Whetstone / Sharpening Stone with grit #220 - #320
We are now talking about the coarsest waterstones.
They remove metal quickly and are a good choice when you need to thin a thick edge or repair chips. If the edge is very worn, it is used to grind away the "shoulders" and create a new V-shape on the edge.
If you have a carbon steel knife with a clear shinogi line, it's a good idea to use these stones to thin the bottom 2 centimeters of the blade. You lay the knife flat on the stone and apply pressure 1 cm above the edge. This grinds the so-called secondary bevel, and you do this partly to keep the edge thin, but also to flatten the grinding surface so that it becomes even and free from low spots that are always present as traces from manufacturing.
It is very difficult to see these irregularities on a new knife because the difference between low and high spots is barely measurable, and they are completely masked by the finish the manufacturer applies to the knife.
So, the coarse waterstones have the same uses as diamond stones, but coarse waterstones do not leave as rough marks as diamond plates, and you get more contact and feel thanks to the slurry the stone produces.
The disadvantage of coarse stones is that they wear a lot and need to be flattened often. The coarse grinding also means that the burr is not as crisp as the burr from a diamond stone or a medium-fine waterstone, and it can be perceived as harder to know when you are done. This is a workhorse that you use when you need to re-grind your chef's knife from scratch. However, you must move on to finer stones to achieve an edge that is shiny and sharp.
#500-800 – The Purification Phase.
A range that lies between coarse and medium. This is rarely a good stone for a beginner who wants to get by with only 1 or 2 stones. For a more advanced sharpener, however, it is a lovely stone that cleans up the scratch pattern from the diamond plate or the coarse #220 stone.
It is particularly used when you are undergoing a multi-stage process to polish what is called a Kasumi finish. Kasumi is a uniform and hazy finish created on the lower part of the blade's side. It is very beautiful, but it is time-consuming because you have to go step by step and successively smooth out the scratch pattern from the previous step.
A #500 stone does this with flying colors, but it is also suitable for regular sharpening of knives that are reasonably worn. Like coarse stones, you must move on to a finer stone before achieving a sharp, good cutting edge.
#1000-2000 – The medium-fine stone.
The most important stone in your arsenal.
It is medium coarse/medium fine and is used every time you sharpen a knife. If the edge is heavily worn, it can take time to achieve a burr in this range. In that case, you need to start with a coarser stone to avoid wearing down the 1000-grit stone for a long time. If, instead, you have a knife whose edge has only become dull, then this is the stone you should start with.
You sharpen the edge at an angle of 10-15 degrees until you feel the jagged burr (also called a wire edge or beard). It forms as a burr on the opposite side to where you have sharpened, and it is proof that you are done, that you have reached the zero point and pushed steel remnants to the other side.
The medium-fine stone is best at creating a crisp and even burr across the entire edge. Once you have achieved a burr from tip to heel, you do the same on the other side. You have now created a distinct V, and it is only now that you achieve true sharpness. We usually call it a V, but it becomes even clearer if you think of the shape of an X. In the middle of an X, you find the zero point where sharpness resides.
It is therefore the intersection where the V shape theoretically continues and would ultimately create an X. As mentioned, the burr is proof that you have reached this zero point, and the medium-fine stone is the tool that gets you there. But are you done already?
Well, you get a perfectly acceptable edge at 1000 grit, but it is rough and hazy and benefits from further polishing before you achieve an edge that impresses.
#3000-6000 – Polishing.
This is a fun and rewarding stage in the sharpening process. Now, we are barely talking about material removal anymore.
Of course, steel is removed, but not to any significant extent. Instead, we are talking about smoothing out the scratch pattern so that the edge becomes shiny and sharp.
A burr can still be created if the edge is very thin and has low mass, but for a "normal knife," it's more about polishing. If you were to put a 1000-grit edge under a microscope, you would see a scratch pattern with large peaks and valleys, like a mountain ridge. It is this serration that we want to smooth out so that you get appropriately sized teeth in the scratch pattern.
But what constitutes appropriate serration? Opinions differ here, and it becomes important to understand why. It simply comes down to what you want to achieve. A medium-coarse 1000-grit edge has relatively coarse teeth. This allows it to grip a tomato very well. You've probably tried dragging an old junk knife against the underside of a plate and noticed that it actually cuts quite well for a few strokes, right?
That's because you have created teeth that grip the tomato, and you cut through the skin without the knife sliding around like a butter knife on an apple. At the same time, the coarse scratch pattern means you don't get impressive sharpness. When you polish the edge from 1000 grit to around 4000 grit, the size of the teeth decreases. You have smoothed out the peaks and valleys in the mountain ridge, and you get a smoother and shinier edge.
Undoubtedly, you also get a sharper edge. Most sharpeners would agree that #1000 provides a somewhat too coarse edge, but where do you draw the line? We are now talking about the infamous "bite," or bite vs. sharpness, if you will. We believe that the 3000-6000 range is very good for a kitchen knife. You get a shiny and extremely sharp knife, but you still need a certain micro-serration that provides good bite. To pinpoint your own preference on the scale, you need to experiment.
It is clear, however, that you will get a good edge in the 2000-6000 grit range, provided your sharpening technique creates a V-shape with a distinct apex.
#8000 and above – Mirror-like for enthusiasts
No one needs to go this high to get a good edge on a kitchen knife. Period.
But then why do such fine stones exist? It is, of course, very rewarding to sharpen an edge that gives a total mirror finish.
It also becomes hysterically sharp, and you can split free-hanging hairs with your freshly sharpened knife. The disadvantage is that the bite becomes low.
The edge will provide a fantastic cutting sensation as long as the tiny teeth can grip the ingredient. But, when the knife loses its initial sharpness, you will more quickly reach a point where the edge starts to slip on the tomato. The knife has lost its bite because the scratch pattern is too fine to maintain its micro-serration.
For this reason, super-fine stones should only be used for hard steels that do not wear as quickly as simpler steels with low HRC. If you were to take a really low-quality knife and polish the edge to 8000 grit, it would also become hysterically sharp.
A few tomatoes later, it feels dull again, and you wish you had stopped at 2000 grit so that the coarser teeth were still there and could work in your favor.
#8000 and above – Mirror finish for enthusiasts
Japanese natural sharpening stones are quarried and come in a variety of finenesses and hardnesses.
Grit is not measured in these stones as they are not synthetically composed and thus do not have an exact grit size (Grit = Grit per inch = Number of grains per square inch). Natural stones are a tool for the truly dedicated.
The right stone for the right edge will produce an extremely polished edge that still retains that famous bite.
Natural stones are also a clear favorite for anyone polishing a kasumi finish.
We touched upon kasumi briefly when discussing medium-grit stones, the clean-up phase, and we will delve a bit deeper into the topic here.
Kasumi means mist or fog in Japanese, and it gets its name from the finish created when you lay the lower part of the blade against the stone and rub it to create a misty finish.
It is by no means trivial. It requires good technique, a good stone, and preparatory work that ensures the entire bevel has been leveled in several stages and is completely free of low spots. If you take the time to "open up" a new carbon steel knife with an iron cladding and work your way to a perfect kasumi, there is nothing more beautiful for a true knife enthusiast.
In short, no one needs a natural stone to create a sharp and good edge on a kitchen knife. But with the right stones, the right knives, and the right technique, you will soon have discovered a passionate interest.
