When to sharpen a knife?

A knife loses its edge from the very first uses. The right moment to sharpen it does not show on a calendar, you feel it as you cut. Here is how to spot that moment and how to space out your sharpenings.

How often should you sharpen a knife?

Sharpen a knife as soon as it shows the first signs of a failing edge, without waiting until it stops cutting. The frequency depends mainly on use, not on a universal rule.

For daily kitchen use, expect a full sharpening every one to six months. The range is wide because it depends on the steel, the cutting surface and everyday upkeep. For lighter use, a few sharpenings a year are often enough. For occasional use, once or twice a year.

These figures are only guides. The blade itself is your best guide. A knife that drags or slides needs sharpening, whatever the date of the last one.

What changes how often you sharpen?

Frequency depends on four concrete factors:

• Intensity of use. The more you cut, the more the edge wears, because every cut abrades it against food and the board.
• Steel hardness. A hard steel holds its edge longer, because it resists edge deformation better. Japanese steels such as VG10 last a long time but stay sensitive to knocks.
• The cutting surface. A wooden or soft plastic board protects the edge. Glass, stone and metal blunt it, because their surface, harder than the blade steel, crushes the edge on every contact.
• Everyday upkeep. Regular use of a honing steel straightens the edge and spaces out sharpenings, because it corrects the deformation before it sets in.

How do you know a knife needs sharpening?

A blunt knife sends clear signals as you use it. Three simple tests confirm the need to sharpen.

The tomato test

Rest the blade on a tomato skin without pressing. A sharp blade bites into the skin on its own. A blunt blade slides or crushes the fruit. The edge no longer bites because it has rounded off.

The paper test

Hold a sheet of paper upright and cut downwards. A sharp knife slices cleanly and evenly. A blunt knife catches, folds or tears the sheet. Paper reveals the smallest flaw in the edge.

Signs during use

Several clues give away a tired blade. The knife tears the onion instead of slicing it, and makes you cry more, because crushed cells release more sulphur compounds. It takes unusual effort. Under the light, the edge reflects bright spots, a sign of rounded areas that catch the light.

Sharpening and honing, two complementary steps

Two different operations keep a knife sharp. One maintains the edge day to day, the other rebuilds it in depth.

Everyday upkeep straightens the edge bent by use. You do it with a honing steel, it removes no metal, and you repeat it often. This step, called honing, is enough as long as the blade stays in good condition.

Sharpening comes in when honing is no longer enough. It removes a thin layer of steel to rebuild a clean edge. You do it on a stone, less often, and it calls for more care. The two are often mixed up, but the action itself differs.

Why not wait until the knife stops cutting?

Sharpening early protects the blade. Waiting until it is fully blunt costs more, both to the blade and to safety.

A very blunt or chipped edge forces you to go deeper into the steel to find a clean edge again. Sharpening then removes a lot of metal at once. Each deep sharpening shortens the knife’s life. Regular upkeep, by contrast, takes off almost nothing each time.

A blunt knife is also more dangerous. It slides instead of biting, which makes you press harder. More pressure means less control and a risk of slipping. A sharp blade cuts where you place it.

How to space out sharpenings?

A few simple habits keep the edge longer and space out sharpenings.

• The board: cut on wood or soft plastic, never on glass, stone or metal, which blunt the edge.
• Storage: keep each knife in a block, on a magnetic bar or in a blade guard. Loose in a drawer, blades knock together and chip.
• Washing: wash by hand and dry straight away. The dishwasher damages the edge and the handle through heat, detergents and knocks.
• The honing steel: run a honing steel regularly to straighten the edge before it bends too far.

Hand sharpening on Japanese water stones

When honing is no longer enough, hand sharpening restores a clean, lasting edge. The Japanese stone remains the reference method for a fine edge.

The water stone, or toishi, removes metal gradually and polishes the edge grain after grain. This slow work shapes an even, lasting edge, hard to obtain with an automatic sharpener. It respects the angle and geometry of each blade.

Togi Toki sharpens knives by hand on Japanese stones, by post. You send your blades, and they come back ready to cut. The service covers France and Europe.

Frequently asked questions

Can you sharpen every knife?

Almost every straight-edged knife can be sharpened, from kitchen knives to pocket knives. Serrated blades and bread knives need a specific technique, best left to a professional. Japanese knives are sharpened at a narrower angle, around fifteen degrees, and cope badly with fixed-angle manual sharpeners.

Does sharpening wear a knife down?

Yes, a little. Each sharpening removes a thin layer of steel to rebuild the edge, which thins the blade over time. Regular upkeep limits this wear, because it takes off very little each time. By contrast, waiting until the blade is fully blunt forces you to remove a lot of steel at once, which shortens its life.

What angle should you sharpen a knife at?

The angle depends on the type of knife. European knives are sharpened at around twenty degrees per side, a solid compromise between fineness and strength. Japanese knives aim for a narrower angle, about fifteen degrees, for a very fine edge. A constant angle on every pass remains the key to a clean, even edge.