Sharpen a kitchen knife properly: proper instructions

A sharp kitchen knife is safer and easier to control than a dull one, provided you use it correctly. Sharpening removes a small amount of metal to recreate the cutting edge; honing straightens an edge that is still present but bent. This guide uses a whetstone because it gives a repeatable result without relying on a powered grinder. Do not practise on a valuable Japanese knife, a serrated knife, a single-bevel speciality knife, or a knife with loose handle scales until you understand its requirements.

What you need

• A stable sharpening stone, preferably a medium stone around 800–1,200 grit and an optional finer stone around 3,000–6,000 grit.
• Water if the stone is a waterstone, or the lubricant specified by the maker. Some stones must not be soaked; follow their instructions.
• A non-slip mat, damp folded tea towel, or stone holder.
• A clean cloth, washing-up liquid, and a dry towel.
• Optional: a marker pen and a leather strop or folded newspaper for final deburring.

Work on a clear, well-lit counter with children and pets away. Keep the blade pointed away from your body and do not try to catch a slipping knife or stone.

Prepare the stone and knife

1. Read the stone maker’s instructions. Soak only a soaking waterstone for the stated time. Splash-and-go waterstones need surface water only. Oilstones need suitable oil, while diamond plates are normally used with water or dry according to their maker. Incorrect preparation can damage the stone or make it ineffective.
2. Put the damp towel or non-slip mat on the counter and place the stone on it lengthways. Press it down and confirm it cannot skate across the surface.
3. Wash and dry the knife so grease and food do not foul the stone. Inspect it for chips, a bent tip, cracks, or a loose handle. Stop if the blade is damaged; severe chips or cracks need professional assessment or replacement.
4. Choose an angle. Many Western-style kitchen knives work around 15–20 degrees per side. If you do not know the original angle, begin around 15 degrees for a thin chef’s knife or 20 degrees for a sturdier general-purpose knife, then keep that angle consistent.
5. Use the marker test if needed: colour the bevel near the edge with marker, make two light passes, and inspect where the ink has been removed. Ink only at the shoulder means the angle is too shallow; ink only at the very edge means it is too steep. Adjust until the pass removes ink across the existing bevel.

Sharpen the first side

1. Place the heel of the blade near the far end of the stone, with the edge facing away from you. Hold the handle securely in your dominant hand. Put the fingertips of the other hand on the flat of the blade, well away from the edge.
2. Raise the spine to your chosen angle. Keep the wrist firm and use light, controlled pressure from the supporting fingertips. The aim is to hold a steady angle, not to press hard.
3. Draw the knife across and down the stone so the whole edge, from heel to tip, contacts the abrasive. Sweep the blade sideways as necessary so the curved tip also travels over the stone. Use a smooth stroke; do not saw aggressively in one small spot.
4. Repeat, checking that you are working the full length evenly. Add water as required for a waterstone, but do not wash away all slurry unless the stone maker directs it.
5. Feel very carefully for a burr on the opposite side. With the knife held edge-up and stationary, move a fingertip from the spine towards the edge, never along the edge. A burr feels like a fine rough catch on the far side. Once it runs from heel to tip, you have reached the edge.

Sharpen the second side and finish

1. Turn the knife over and repeat the same strokes at the same angle until the burr flips back to the first side along the full edge. Use the same approximate number of strokes and pressure, but let the burr be your guide rather than counting alone.
2. Reduce pressure for several alternating strokes, one per side. This refines the edge and reduces the burr. On a finer stone, repeat with light alternating passes if you want a smoother cutting edge.
3. Optional: strop with the blade travelling spine-first, away from the cutting edge. A few light alternating passes on leather or folded newspaper can remove the last trace of burr. Never push the sharp edge into a strop.
4. Wash the knife to remove abrasive residue, dry it fully, and clean and dry the stone according to its instructions. Store the knife in a block, guard, magnetic rack or drawer organiser where the edge is protected.

Test and confirm

Use food, not your thumb, to test sharpness. A ripe tomato should slice with gentle forward-and-back motion rather than crushing. A sheet of paper should cut cleanly when you draw the knife through it; do not hold paper near the cutting path. Check several sections: heel, middle and tip. If one part snags, return to the stone for a few controlled strokes in that area, then repeat light alternating passes.

A sharp edge can still feel poor if it has a remaining burr. If it cuts one direction well but catches or tears in the other, strop lightly or make a few very light alternating stone passes. Avoid repeatedly testing on hard surfaces, glass plates, ceramic mugs or your fingernail: they can damage the edge or injure you.

Common mistakes and safety

• Do not use heavy pressure. It makes the angle wander, gouges soft stones and creates a large stubborn burr.
• Do not chase a mirror polish before forming a continuous burr on the medium stone. The edge must be properly apexed first.
• Do not let the knife’s tip run off the stone without control. Slow down at the curved section to avoid rounding the tip or cutting a hand.
• Do not use a honing rod as a substitute for sharpening a truly dull knife. Hone only after sharpening, or between sharpenings when the edge is merely rolled.
• Do not put a sharp knife loose into a washing-up bowl or drawer. Wash it separately, dry it straight away and store it protected.
• Stop if you are tired, rushed or distracted. Put the knife flat on the counter with the edge facing away until you can continue safely.