The edge can also bend or fold over - not something you'd be able to see with the naked eye. When you sharpen a knife, you are grinding away some of the metal to reintroduce the proper sharp angle.
• Know how to recognize when your knife needs to be sharpened. The whole point of a sharp knife is to help you work efficiently, easily slicing through food without having to exert too much pressure. Dull knives can also cause accidents when they slip over rather than cut through food.
Arnold suggests tomatoes, lemons, bell peppers and carrots as effective foods for testing whether your knife needs to be resharpened. Also, onions. It won't work for everyone since sensitivity to the tear-producing chemical varies, but Arnold says a dull knife is likely to break open more onion cells and release more juices than a sharp knife that creates a clean cut.
The cool-looking test that involves seeing how well a knife cuts through paper can be a little iffy, too. Even a sharp - but not perfectly sharp - knife might struggle to cut the paper. Arnold also points out that the thickness of some paper products - printer paper, note pads, etc. - can vary and give you inconclusive results. If he's going to do the paper test, he relies on something like newsprint or coupon inserts, which generally have a consistent makeup.
If you're worried that getting your knives professionally sharpened is too expensive to justify, you can rest easy. Most professionals will charge less than $10 to sharpen a standard chef's knife.
• Think about honing your knives. Even if you know to sharpen your knives, you may not be as familiar with the concept of honing. Honing does not sharpen the blade. Instead, Arnold says, it realigns the blade, correcting the bending or folding described above.
Honing can be done on a steel that looks a bit like a dagger (see the photo at the top of the page). You'll often find them included in knife sets, but Arnold prefers the quality of steels you buy a la carte. He recommends a diamond-coated one from Messermeister, which costs around $30. Other types are available in the $15 range.
To hone your blade, lightly run the edge of the knife at a 15- or 20-degree angle along the steel. Three times on each side of the blade should be sufficient, Arnold says. Ideally, you'd be doing this before (or after) every time you use your knife, but we're not idealists here. Let's get practical: Even doing it every so often will help. If honing isn't something you're interested in, you won't necessarily ruin your knife; you'll just need to have it sharpened more often.
• Use the right board. Hard surfaces can dull or even chip a knife. Wooden or plastic boards are good choices, Arnold says. And as we've mentioned here before, when it comes to cutting boards, bigger is better.
• Clean them properly. Hand-washing is the best way to clean your knives. Dishwashers can be especially hard on knife handles, causing them to discolor, crack or separate from the blade. The racks or utensil basket can damage the blades and vice versa, and fishing a knife out of the dishwasher isn't a recipe for safety, either. After you wash a knife - a sponge with warm water and soap will do - dry it thoroughly, and carefully, with a towel. Do not store it dirty or wet unless you want it to rust.
• Store them the right way. Protect the blade, protect yourself. Never should you leave a knife blade exposed in a way that could cause injury. I prefer plastic sheathes on knives so I can keep them in a drawer. Wooden blocks are acceptable, too, as are magnetic strips on the wall, so long as they're not within reach of curious children or in a place where people are prone to bumping into them.
