How to Sharpen a Knife
All you need to know about sharpening your own knife
Every knife becomes dull after a while. By sharpening your knife regularly it will keep on cutting well. You can bring all your knives to our sharpening shop. You can also (for the most part) take care of it yourself.
But how do you sharpen a knife? We start by explaining why a knife needs to be sharpened.
Do you already know how to sharpen your knife? Click here for all our sharpening tips
Is my knife still sharp?
The illustration above shows the cross-section of a knife blade. A sharp knife has a sharp V-shape at the cutting edge. If the two cutting edges come together in a sharp point, as shown in the illustration on the left, the knife will cut through food with ease. After some time of cutting, a burr will appear at the fold. You will notice that the knife is not cutting as well as it should.
There are several ways to check if your knife is still sharp:
Paper test
Put a piece of paper in one hand and cut the paper with the knife in the other hand. This should work without tearing.
Tomato test
You can also test it with a tomato. The hard and smooth skin of a tomato quickly shows if a knife is blunt. When a knife is sharp, you can cut a tomato without force. Your knife is blunt when you have to apply extra force and the tomato is crushed.
Nail test
Another way is to hold your fingernail at an angle of 45 degrees. See if your knife can stay straight on it. If it slips, then the knife is blunt.
Sharpening with a sharpening steel
You can sharpen a European kitchen knife on a sharpening steel. This will straighten the burr just before cutting, allowing the knife to cut smoothly through the food. With Japanese knives or knives with a hardness of 59 HRC or higher this is not possible. The steel of the knife is harder than the steel of the sharpening steel and will eventually damage both.
Do you have a Japanese knife? Then read on, under the heading 'Sharpening'.
To sharpen a knife
The easiest way is to place the sharpening steel pointing downwards on a table or countertop. Place the knife at an angle of 20 degrees to the top of the sharpening steel.
Pull the knife with a smooth and gentle movement backwards and downwards. There is little force required, and speed is not essential.
It is important to keep the angle the same, so take your time. Always switch sides, so both sides are sharpened the same amount of times. After 6-8 repetitions the knife should be sharp again. During the last few strokes you hardly need to apply force, the weight of the knife is enough.
Sharpening ≠ sharpening
Contrary to popular belief a sharpening steel does not sharpen. It only straightens the burr. Therefore this kind of intermediate maintenance is of no use anymore.
If the fold of your knife really looks like the middle picture of the three blades, then it really needs to be brought back to its original v-shape. To achieve this you have to take some material from both sides. This is called sharpening.
Sharpening
After a while it becomes necessary to sharpen a knife. The dotted line in the third picture at the top of this page shows how to sharpen the blade. This gives the fold of the blade a sharp v-shape again. If you want to sharpen a knife yourself there are several methods and materials. The most common is a diamond or ceramic sharpening rod and sharpening stones.
Sharpening tools
A sharpening rod is handy because it's straightforward to use and doesn't take much time. The technique is the same as sharpening with a sharpening steel.
Diamond sharpening bar
This (often oval) bar contains diamond dust that sharpens the material of your knife as you pass it. This works fast and is very effective. The disadvantage is that it is quite coarse. If you look through a microscope, you will see that the fold is somewhat coarsely ground.
Ceramic sharpening rods
A ceramic sharpening bar is made of fine ceramics and sharpens much finer than a diamond bar. It is therefore preferred because it gives a nicer and sharper result. The various models differ slightly in fineness. In general, you can say that the more expensive models are made of finer ceramics and give a sharper result. Some of them also have two coarsenesses, a fine and an extra fine side.
The disadvantage of a ceramic sharpening rod is that it is vulnerable. If it falls, chances are it will no longer be usable. There is also a ceramic sharpening rod from Kazoku that has a steel core. This one has a smaller chance of breaking.
Sharpening stones
Sharpening on stones is the most beautiful way of sharpening. With the right stones and technique, your knives will be sharper than ever.
The disadvantage compared to a sharpening rod is that it takes more time to sharpen the knife. You really need to take your time. You will also need several stones, or several grain sizes, so you will have to spend more money.
There is a lot of information online about sharpening with whetstones. However, all this information makes many people doubt too much. It is best to start with a reasonably good (not too expensive) knife because a cheap knife will not sharpen very well. It would be a shame to ruin an expensive knife.
The degree of bluntness of your knife determines which grit you should start with. A low number indicates a coarse grain. For a knife of which the fold really needs to be repaired, you need about 240 grit. This will lay the foundation for a new v-shape in the blade. After that, you can start grinding with 600-800 grit and then 3000-6000 grit. From 3000-grit onwards you can start polishing the knife for a super-sharp result.
How to sharpen on a whetstone
There are several techniques for sharpening on a whetstone. You can do it in long strokes or with several short drag strokes. Both techniques will result in a sharp knife. The most important thing is to keep the angle constant.
How to determine the angle
Many beginners find determining the angle difficult. We therefore advise you not to pay too much attention to the angle in the beginning. It is better to make sure that you are constantly sharpening the knife to the same angle. So don't sharpen your knife at 17 degrees one day and 14 degrees the next. This way your knife will never be as sharp as it was before.
Is it a European knife? Then sharpen it at about 20 degrees. Japanese knives are best sharpened at 15 degrees. Of course you are completely free in this. Some experienced sharpeners sharpen their knives at 10 degrees. This will give you a sharper knife but it will also lose its sharpness faster so you will have to sharpen it more often.
How often should you sharpen each side
You keep sharpening until you get a burr on the other side. You can feel this by "stroking" the edge with your fingertips. Do you feel a subtle resistance over the whole blade? Then turn the knife over and sharpen the other side. Do this until you feel another burr on the other side. Did you feel a burr on both sides? Then you can change the stone for one with a higher grit.
Finished sharpening? Then pass both sides of the stone at a higher angle. This will remove the last burrs. Want an even finer cut? Then we recommend using a sling as a next step.
Strop
Theoretically, when sharpening on a stone, you always end up with a burr. Even if you end up with a very fine grain. To remove this last (minuscule) burr you can poach the knife. This means that you stroke the fold of the knife over a piece of leather. Often this leather is glued on a piece of wood. Because the soft leather is on a hard surface the effect is that the leather is very light and flexible around the fold. Something you can never achieve with a stone.
For stropping to be successful the knife has to be sharpened sufficiently. Otherwise stropping is useless. Also it is only possible to slip a knife with a straight fold.
The Kazoku leather Strop block is superb and has an excellent price-quality ratio.
When you are stroking you move the knife differently than when you are using a whetstone. If you move the knife with the fold first over the strop it will cut into the leather. Therefore, you move the knife in the direction of the back.
Sharpening course
Want to learn from a Master Sharpener? Then follow our course.