How to Sharpen a Kitchen Knife at Home With a Whetstone

If your knife slides off a tomato skin instead of biting into it, the blade is not ruined. It is dull, and that is the most fixable problem in the whole kitchen. Learning how to sharpen a kitchen knife on a whetstone takes about twenty minutes of practice, a stone that costs less than a dinner out, and a little patience with the angle.

A dull knife is also the more dangerous knife. It needs more pressure, so when it skids on an onion it skids hard, usually toward your fingers. A sharp edge goes where you aim it. Here is the method I teach in cooking classes, from choosing a stone to the paper test at the end.

Sharpening Versus Honing

These two words get mixed up constantly, and the difference decides what you actually need to do.

• Honing straightens an edge that has rolled over slightly from use. A honing steel does this in six or eight strokes and removes almost no metal. Do it every few cooking sessions.
• Sharpening grinds away metal to create a fresh edge. You need a stone, a pull through sharpener or a professional. A home cook who cooks most nights needs this every two to four months.

If honing no longer brings the knife back, it is time to sharpen. A quick check: hold the blade under a bright light, edge facing you. Any shiny glints along the edge are flat, worn spots that need grinding.

Choosing a Whetstone

Whetstones are rated by grit. Lower numbers are coarser and remove metal faster; higher numbers polish.

For most kitchens, a combination stone with 1000 grit on one side and 6000 on the other is the sweet spot. Expect to pay around 25 to 45 for a decent one. Most are "splash and go" or need soaking for 10 to 15 minutes before use; the packaging will tell you which. A soaking stone is ready when it stops releasing bubbles.

Find and Hold the Right Angle

The angle is where beginners struggle, so set it before you take a single stroke. Most Western kitchen knives, such as German chef's knives, are sharpened at about 20 degrees per side. Japanese knives are usually thinner and sit closer to 15 degrees.

A simple way to find 20 degrees: hold the blade straight up at 90 degrees to the stone, then halve it to 45, then halve again to roughly 22. Lower it just a touch from there. For 15 degrees, a stack of two coins under the spine of a typical chef's knife gets you close.

Consistency matters more than precision. An edge held at a steady 18 degrees beats one that wobbles between 15 and 25 on every stroke.

How to Sharpen a Kitchen Knife, Step by Step

Put the stone on a damp tea towel or its rubber base so it cannot slide, 1000 grit side up. Keep a cup of water nearby to splash on the surface whenever it looks dry.

1. Start at the heel. Lay the knife edge away from you at your chosen angle, with the heel of the blade on the near end of the stone.
2. Push and sweep. With two or three fingertips of your other hand pressing gently on the flat of the blade, push forward and across so the whole edge, heel to tip, crosses the stone in one stroke.
3. Use light pressure. About the weight of a bag of sugar is enough. Let the stone do the work.
4. Repeat ten to fifteen strokes on the first side, then feel for a burr.
5. Switch sides and repeat the same number of strokes until a burr forms on the other side too.
6. Refine by flipping to the 6000 grit side and making ten lighter alternating strokes, one per side.

What a Burr Feels Like

The burr is a tiny wire of metal that curls over to the opposite side once you have ground all the way to the edge. Run your thumb gently from the spine toward the edge, never along it, on the side you are not sharpening. A slight catch along the whole length means you are done with that side. No catch near the tip usually means you lifted the handle too little as you swept.

Test the Edge and Clean Up

Hold a sheet of printer paper up by one corner and slice down through it. A sharp knife cuts cleanly with no tearing or snagging. A ripe tomato is the second test: the blade should break the skin under its own weight with only a light draw.

Rinse and dry the knife immediately, wipe the stone and let it air dry fully before putting it away, which can take a day for a soaking stone. Never store a damp stone in a closed box, or it can crack and grow mould.

To keep the edge longer, cut on wood or plastic, never glass, slate or the countertop. If you are tempted to make your own, see our piece on building your own wooden cutting board and utensils.

Common Mistakes and When to Get Help

• Pressing too hard. Heavy pressure rounds the edge and gouges the stone.
• Skipping the tip. Lift the handle slightly as the curved front of the blade crosses the stone.
• Using a dished stone. Stones wear into a dip over time. Flatten yours every few months on a sheet of wet sandpaper taped to a flat surface.
• Sharpening serrated knives the same way. Bread knives need a tapered rod for each serration, or a professional.

Expensive, very hard Japanese steel or a badly chipped blade is worth taking to a professional sharpener the first time. And if you are still choosing a knife to practise on, start with our advice on the one knife worth buying before anything else.

FAQ

How often should you sharpen a kitchen knife?

Sharpen a kitchen knife every two to four months if you cook most days, and hone it every few uses in between. Light home use can stretch sharpening to twice a year.

Are pull through knife sharpeners bad?

Pull through sharpeners are not bad, but they remove more metal and leave a rougher edge than a whetstone. They are fine for cheap knives and quick fixes, less so for good knives you want to keep for decades.

Do you need to soak a whetstone?

Only some whetstones need soaking. Traditional soaking stones need 10 to 15 minutes in water, while splash and go stones just need water sprinkled on the surface before use.

A Sharp Knife Is a Habit

Get a 1000 and 6000 grit stone, hold a steady 15 to 20 degree angle, raise a burr on each side and finish with light polishing strokes. After your third or fourth session it becomes a calm ten minute job. Find more tools worth owning in our kitchen gear guides.