How to Sharpen a Knife

Almost every complaint about a kitchen knife is really a complaint about a dull one. A blunt knife slips off tomato skin, crushes herbs instead of cutting them, and is considerably more likely to cut you, because you push harder and the blade goes where it wants rather than where you aimed it.

The good news is that sharpening is not a craft skill requiring years of apprenticeship. It is three ideas and about fifteen minutes.

Honing and sharpening are different jobs

This trips up almost everyone, and getting it straight saves a lot of wasted effort.

Honing — what you do with the steel rod that came with your knife block — removes no metal. The very edge of a knife is thin enough to bend, and normal use rolls it over to one side. A honing rod pushes it back upright. Ten seconds, and the knife feels sharp again.

Sharpening removes metal to grind a new edge. You do this when honing stops working, because the edge is no longer bent — it is worn away.

For a home cook: hone every week or two, sharpen two or three times a year. If you find yourself honing before every single use and it barely helps, you are overdue for a sharpen. There is more detail in how often you should sharpen your knives.

What you need

A whetstone. A combination stone with roughly 1000 grit on one side and 3000–6000 on the other covers everything a kitchen knife needs. The 1000 side does the actual sharpening; the fine side refines the edge. If you buy only one stone, make it 1000.

Skip pull-through sharpeners with carbide V-slots. They tear metal out rather than grinding it, and on a hard Japanese blade at 60+ HRC they will chip the edge. They exist because they are easy, not because they work. See the best whetstones for what to actually buy.

A non-slip base. Most stones come with a rubber holder. A damp tea towel under the stone works just as well and is what most people end up using.

Water. Soaking stones go in water for five to ten minutes until bubbles stop rising. Splash-and-go stones just need the surface wet. Check which kind you have — soaking a splash-and-go stone can crack it.

That is the entire kit. No jigs, no guides, no machines.

Step 1: find the angle and stop thinking about it

The angle between blade and stone is the only thing that really matters, and the number is less important than holding it steady.

• German knives (Wüsthof, Zwilling, Mercer, Victorinox) are ground around 14–15° per side.
• Japanese knives (Shun, Global, Tojiro, MAC) are usually 10–16° per side.

Two ways to find it without measuring anything:

The paper trick. Fold a sheet of paper in half, then in half again. That corner is about 22°. Half of that is roughly your target for a German knife. It is a rough guide, and rough is fine.

The two-coin trick. Two stacked coins under the spine of an 8-inch blade puts you in the right neighbourhood. Set the knife on the coins, note how the wrist feels, remove the coins, keep the feel.

The thing that actually determines your result is consistency. An edge sharpened at a wobbly 12–18° will be worse than one sharpened at a steady, slightly-wrong 20°. Lock your wrist, move from the shoulder, and let the whole arm travel rather than the hand.

If you want to be certain you are hitting the edge and not the shoulder of the bevel, colour the bevel with a marker pen and take two or three strokes. Where the ink is gone is where you are grinding. Adjust until the ink disappears right at the edge.

Step 2: raise a burr on one side

This is the step people skip, and skipping it is why their knives never get sharp.

Lay the blade on the stone at your angle, edge facing away from you. Push it forward across the stone as if you were trying to shave a thin layer off the surface, moving the blade sideways as you go so the whole edge — heel to tip — passes over the stone. Light pressure. The stone does the work; leaning on it just wears the stone unevenly.

Do ten strokes, then check for a burr.

A burr is a thin wire of metal that folds over onto the far side of the edge. It is the physical proof that you have ground all the way to the apex. Find it by running a fingertip across the blade — from spine toward the edge, never along it — on the side facing away from the stone. It feels like a faint catch, a roughness that was not there before.

Keep going until you can feel the burr along the entire length of the edge, including right at the tip and right at the heel, which are the two places it usually goes missing. On a genuinely dull knife this can take a few minutes on a 1000 stone. That is normal.

Do not move on until the burr runs the full length. No burr means the two bevels have not met, which means there is still a flat, dull strip at the very edge. Everything after this step is polishing that dullness.

Step 3: raise the burr on the other side

Flip the knife and repeat, same angle, same pressure. The burr will move over to the first side.

You will feel it flip. That is the signal that this side has reached the apex too. Usually it takes fewer strokes than the first side.

Step 4: refine, and make the burr smaller

Now alternate sides — five strokes left, five right, then three and three, then one and one — with progressively lighter pressure. Each pass makes the burr smaller and the edge closer to a true point.

Switch to the fine side of the stone and repeat the alternating passes with barely any pressure at all. This does not make the knife much sharper in any way you will notice while cooking, but it makes the edge last longer, because a polished edge has fewer weak points to break off.

Step 5: remove the burr properly

The burr has to come off, and it must come off cleanly. A knife that still has its burr feels wonderfully sharp for about four cuts, then the wire folds over or snaps off and takes part of the edge with it. This is why a knife can feel razor-sharp on the stone and dull the same evening.

Two ways to finish:

• Very light alternating passes. One stroke per side at your sharpening angle, using almost no pressure — the weight of the blade is close to enough. Three or four alternations and the wire is gone.
• Strop it. Draw the blade backwards, spine-first, along a leather strop, a piece of cardboard, or the back of a leather belt. Ten passes per side. This is the most reliable way to remove a burr without creating a new one.

Check the edge again with a fingertip across the blade. It should feel clean and sharp on both sides, with no catch anywhere.

Step 6: test it

Three tests, in increasing order of usefulness:

1. Paper. Hold a sheet in the air and slice down from the heel. A sharp knife cuts cleanly the whole length; snagging in one spot means that section did not get a full burr.
2. A tomato, no pressure. Rest the blade on the skin and draw it back. It should break the skin on its own weight. This is the test that matches how you actually cook.
3. How it feels tomorrow. A properly deburred edge is still sharp after a week of dinners. An edge that felt incredible on Sunday and average on Wednesday had a burr left on it.

Nobody needs to shave their arm. It looks impressive and tells you nothing about how the knife handles an onion.

Common mistakes

Too much pressure. Sharpening is not a strength activity. Heavy pressure makes a bigger burr, hollows out the stone, and rounds the edge on the way back. Light and consistent beats hard and fast.

Lifting the wrist at the tip. The last few centimetres of the blade curve upward, so if your wrist does not follow, the tip never touches the stone. Lift the handle slightly as you reach the tip so the section under the blade stays flat against the stone.

Stopping before the burr. Ten minutes of confident polishing on an edge that never met itself produces a shiny, dull knife.

Ignoring the stone's flatness. Stones wear hollow in the middle. A dished stone rounds your edge no matter how good your technique is. Flatten it occasionally with a flattening plate or coarse sandpaper on glass.

Cutting on the wrong surface afterwards. Glass, granite and ceramic boards undo an edge within a single meal. If you have just spent fifteen minutes sharpening, the board matters — see cutting boards that protect your edge.

Special cases

Carbon steel knives sharpen faster and rust faster. Dry the blade immediately after sharpening and wipe it with a drop of neutral oil. Full routine in how to care for carbon steel knives.

Hard Japanese knives at 60+ HRC take longer on the stone and reward the fine grit more. Never use a honing steel with ribs on them — a smooth ceramic rod, or nothing.

Single-bevel Japanese knives — yanagiba, usuba, deba — are sharpened almost entirely on one side, with only a light pass on the flat back. If you are unsure whether your knife is single or double bevel, this explains how to tell.

Serrated bread knives cannot be sharpened this way at all. Each scallop needs a tapered rod, and honestly, a bread knife that has gone dull after a decade is usually cheaper to replace.

How long it should take

The first knife you ever sharpen might take half an hour, mostly spent hunting for the burr and second-guessing the angle. By the fourth or fifth knife it settles at ten to fifteen minutes for a properly dull knife, and about five for one you have kept up with.

That is two or three sessions a year per knife. Set against a knife that works properly every time you pick it up, it is the best return on time in the whole kitchen.