When a whetstone is used to cut metal, it acts like sandpaper by removing small particles of metal (aka “swarf”) with each pass of the blade over the stone. Therefore, whetstones with more coarse grits cut faster than those with finer grits and, at the same time, soft whetstones cut faster than hard whetstones because each pass of the blade over both types of whetstones not only removes fine particles of metal from the blade, it also removes fine particles from the surface of the whetstone (aka “slurry”) which continuously exposes new cutting crystals. However, if the swarf is allowed to build up on the surface of the whetstone during sharpening, it will clog the stone and drastically diminish its effectiveness. Therefore, some whetstones require water to lubricate the stone and suspend the swarf whereas, other whetstones require oil to lubricate the stone and suspend the swarf.
The humble sharpener tends to elicit more divergent opinions than just about any other type of kitchen tech. Everyone, it turns out, has their own take on which type of sharpener works best and why and most serious chefs aren’t shy about voicing their opinion. As you can imagine then there are a number of things most chefs – both professional and amateur – look for in a sharpener in order to ensure they get the one that’s right for them. These considerations include:
The sharpener has come a long way in the past couple of thousand years and yet it hasn’t. That is, while there have been incredible advances in the development of mechanical knife sharpeners the classic and very ancient sharpening stone is still with us and very much in use as you read this. The best knife sharpener for you will be one that meets the needs of your cuisine and your temperament but which, first and foremost, reliably produces the sharp knives (look after your knife!) you need with the least hassle.
Whichever method you choose, be it a waterstone (also known as a whetstone), or a pull-through (either V-shaped or ceramic wheels) it's important to regularly hone your knife with a honing steel, which we'll also cover below. You'll be pleased to hear that you won't have to reach for the stones too regularly – once every two or three months should suffice.
Now you may wonder, if a finer stone produces a better cutting edge why do I need a coarse stone at all? The answer is that finer stones work much more slowly than coarse ones. The amount of metal a fine stone removes with each pass is much less than what a coarse stone removes. If you have an edge with a good shape to it from a coarse stone, this is not a problem because the fine stone doesn’t have to remove much metal to improve the edge. If the edge is dull, it will take many times longer to reshape it with a fine stone than it would with a coarse one.