How to sharpen knives
Learn to keep your knives as sharp as possible for precision and safety
Knives are the most important tool in the kitchen. But, however good your knife is, without regular honing or sharpening, a knife it will lose its edge. Having a sharp knife is a must for any serious cook. Not only is it more efficient, but safer too; a blunt knife is more likely to slip, increasing the likelihood of you cutting yourself.
Working with a knife at its maximum sharpness is the easiest way to improve your kitchen skills. Not only will it ensure you're chopping more accurately (meaning less waste) but it will make things easier on the arm and wrist as you’ll need to apply less pressure.
Whether your knives are expensive or cheap, one thing they must always be is sharp.
How to sharpen a knife
Before we go into the tools available, we should talk about the difference between honing and sharpening.
Honing is keeping the edge on a knife sharp. To hone, you use a steel, and while this will prolong the sharpness of your knife, it won’t sharpen a blunt knife or keep a knife sharp forever.
Sharpening is grinding the edge back to a point of maximum sharpness. A good knife should last beyond a lifetime and will need to be sharpened at points, but regular honing will keep it sharp for a lot longer and means you don’t grind away too much of the original shape.
How to use a steel
Confusingly, steels are sometimes called sharpening steels, and though your knife will feel sharper after using one, remember you are honing and not sharpening it.
In other words, honing resets the edge the knife was given when it was last sharpened. With use, that edge will get worn down and the knife will need to be sharpened, but using a steel regularly will keep the edge for three times longer than not using one. Learning to use a steel is a skill and takes a bit of practise, but start slowly and you’ll get the hang of it.
- Hold the steel firmly and vertically against a surface: a heavy wooden board is ideal. If the surface is slippery use a cloth to steady the steel.
- Starting at the top of the steel, place the heal of the knife at an angle of between 15 and 20 degrees against the steel. For thicker European knives you generally want to hold the knife at 20 degrees, and finer Japanese knives at 15 degrees, but anything between the two is fine. See below for how to work out an angle.
- Draw the knife along the length of the steel to its point applying a bit of pressure – as if the steel was a stick that the knife was wittling the bark from. Repeat with the other side. Generally, 3-5 strokes on each side with adequate pressure should be enough. Wipe the blade clean and it’s ready to use.
For a visual representation, watch our video on how to use a steel and sharpening gadgets.
Is my knife blunt?
If a knife doesn’t glide through easily when you're chopping or if it’s starting to slip, then your knife is beginning to lose its edge. As a guide, a sharp, non-serrated knife should cut cleanly through a sheet of paper, and it shouldn't struggle with notoriously tough tomato or pepper skins. If it does, then try honing your knife on a steel. If it’s still not up to scratch then it will need sharpening.
Sharpening a knife
Sharpening a knife will remove considerably more steel from the knife than just honing it. A totally blunt knife will need to be sharpened professionally, or you can invest in an electric sharpener to bring it to its full potential but if it’s just a bit dull and the edge needs grinding there are lots of inexpensive home knife sharpeners available to varying degrees of success, or you can use a whetstone, also known as a sharpening stone.
How to use a whetstone or sharpening stone
This takes a lot of practise but once you’ve learnt how, it’s a cheap and accessible way of putting a very sharp edge on a knife. There are lots of different grades of whetstones available and – as with sandpaper – the higher the number, the finer the grit or the surface. Most whetstones are double-sided and have a different grade on each side. For general use, a stone that’s 1000/6000 is fine.
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We advise buying a stone with a base to keep it sturdy. One with an angle guide is also useful.
- Soak the stone in water for about 10 mins, there should be no more bubbles coming from the stone.
- If the stone hasn’t got a base secure it with, fold a tea towel and set the stone portrait in front of you with the coarse grit side up. Even if you have a base, a fair bit of water comes off the stone, so a tea towel is a wise choice anyway.
- Drizzle a bit more water over the stone and place the tip of the blade against the stone at a 20-degree angle (see how to tell an angle). Draw the knife along stone applying a bit pressure as if you were shaving a thin layer off the top.
- Turn the knife over and draw it back to you. A fine gritty sludge will build up which is perfectly normal. Repeat the process four times or more until your knife is sharp again. Turn the stone over and do it once or twice on the finer side. Clean your knife and the stone and the knife is ready to use.
The right angle
Success with a steel and a whetstone is all about the angle you hold the knife against the tool. A few degrees out won’t matter but how do you know what the angle is?
If you hold the knife with its blade vertically against the stone or horizontally against the steel that’s 90 degrees. Halve that angle and it’s 45 degrees. Halve it again and it’s about 22 degrees – now you're around the area you want to be in to sharpen your knife. From here you can make minor adjustments to make the angle between 20-15 degrees.
Can you sharpen a bread knife?
A bread knife relies on the sawing motion of the teeth as much as the sharpness of the blade. If you were to sharpen a bread knife using any of the methods we’ve mentioned, you’ll blunt the teeth.
Knife sharpening gadgets claim to be able to sharpen bread knives, but we don’t recommend trying them.
To keep the teeth as pointed as possible it’s best to not sharpen and simply replace, but if you invest in a good bread knife, and only ever use it for what it’s intended, it should last a lifetime anyway.
How often should you sharpen a knife?
To keep a knife at its best, a few swipes on a steel, honing the edge before you use it, is good practice to prolong its sharpness. Then, it’s simply a case of sharpening your knife when you need to. In the BBC Good Food kitchen, we get our knives sharpened every couple of months, but they do see a lot of action.