Keeping your knife sharp

Keeping your knife sharp

November 17, 2006, 5:34 am
Filed under: Food

So that this blog isn’t entirely political, I’m doing an entry on cooking. I’ve noticed that almost (except me) has knives that are pretty much blunt. Hardly anyone seems to know what to do to keep a knife sharp, or why.

Having a sharp knife makes so much difference to cooking. It makes it quicker, more efficient, and actually more pleasurable. It also enables you to do things you wouldn’t have been able to do before. The onion for a risotto should ideally be chopped as finely as grains of rice, but this would be nightmarish with a blunt knife. Matchstick thin strips of bacon or vegetables take so long with a blunt knife that it’s not even worth thinking about with a blunt knife. When you carve meat, particularly rare beef or lamb, you need to cut across the grain and very thin to make it as tender as possible (you’re reducing the amount of work your jaw has to do). Slicing it thin enough with a blunt knife is pretty much impossible, so with a blunt knife you tend to resort to just hacking off lumps of meat (or using an electric serrated blade). So having a sharp knife is well worth while.

The basic procedure is as follows (more details below):

• Start by getting the knife sharpened properly. You can either do this by hand with a whetstone or you can just have it done professionally. It’s usually not very expensive (about £3 near me). This needs to be done about every 6 months if you’re using them properly and keeping them sharp. Some of the better ‘knife sharpeners’ (sometimes called ‘diamond hones’) can do this too, but if you have a really blunt knife it would take a monumental effort to get it sharp using one of these.
• Each time you use the knife, steel it beforehand. Steeling a knife doesn’t sharpen it, it just stops it from going blunt.
• Store it so that it isn’t in contact with other metal. Don’t have a ‘knife drawer’ where they are all clanking around in contact with each other.

Knife edge and steeling

To understand what steeling does and why you should do it, you need to have a picture of what the knife edge is like. You can’t see this with the naked eye, but you can imagine it.

A properly sharp knife has an edge like you would imagine it, picture (1) above. If you had an infinitely hard metal, it would stay like this. The metal in real knives though bends when you chop with it. After you’ve finished making your dinner, your knife edge might look like picture (2) above. If you keep using your knife, it will look like picture (3) and then eventually the edge will snap off and you’ll have a very blunt knife. Most people’s knives seem to be in this state.

The point of steeling a knife is to go from picture (2) to picture (1), it’s called “realigning”. All you do is very gently run the knife edge along the steel (the weight of the knife is enough). Do this a few times on each side, gradually decreasing the number of times (one web site suggests 5 times on each side, then 3, 2, 1). Steeling doesn’t sharpen it at all, and will do nothing to an already blunt knife.
If you wash and dry your knife immediately after using it, steel it, and store it so that it’s not in contact with other metal, it should last a good 6 months and stay seriously sharp.

Grinding an edge

Unless you’re quite enthusiastic, it’s probably best to just get someone to do this for you every 6 months. But if you’re like me, a sucker for punishment, you’ll want to do it yourself.

The two pieces of equipment you need are a whetstone, and knife guides. The whetstone is (as the name suggests) a stone. You use it to grind the edge of the knife. A knife guide is a little clip that you fasten to the back of the knife that holds the blade at a fixed angle to the stone (see the picture below). The point of this is that as you are grinding away at the metal, you are forming a flat edge. It is possible to do it by hand, but it’s very skillful and most likely you’ll just end up grinding ineffectually.

Once you’ve got the guide on, you just press the knife against the stone, and move it backwards and forwards or in a circular motion, grinding away. There is a trick to knowing when you’ve done enough. If you run a thumb or finger across the edge (not along it, that’ll end badly), it will normally feel smooth. At a certain point after you have ground for long enough (which might be a long time if you’re sharpening a blunt knife for the first time), you will feel a little roughness as you run your thumb across the edge on the other side from the one you’re grinding on. This roughness is called the “burr”. What has happened is that the side you’re grinding on has become flat, and at the very tip, metal has moved round to the other side. See the picture below.

When you can feel the burr, turn the knife over and grind the other side. Keep feeling for the burr. When you get the burr on the other side, the knife is almost sharp. If you now feel for the burr on the side you have just been grinding, it won’t be there. But if you grind just for a moment on the first side again, you should feel that the burr reappear almost instantly. Now you need to grind away the burr by grinding on one side then the other repeatedly, doing so more and more softly until you can’t feel a burr on either side.

Angles

Depending on what angle you want to grind at, your knife will have different properties. Very shallow angles make the blade extremely sharp, but it won’t keep it’s edge for very long. Wider angles make it less sharp, but keep their edge for longer. It might be sensible to have more than one knife ground at different angles for different purposes. For example, cutting through meat and fat requires a sharper knife than peeling a potato (although personally I like to use a very sharp one for this too).

References and other sources

There are some great web pages on knife sharpening now. The first one to look at is probably the video on YouTube showing TV chef Alton Brown talking about it. There is a good step by step guide here showing you how to do the grinding part. If you want much more detailed information, then look either here or here.

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