Keeping knives sharp

A knife goes dull in two ways, and they need different fixes. Most often the very edge folds over to one side, so the knife cuts badly long before it's actually worn. Honing pushes it back. Sharpening is for when the edge really is worn away and steel has to come off.

The usual line is that a honing rod only straightens. Todd at Science of Sharp cut edges open and looked at them under an electron microscope, and found that steel and ceramic rods do also remove a little metal and form a tiny secondary bevel. That keeps the edge keen, but it doesn't thin the blade the way a stone does.

• Honing: a few light strokes on a rod, about once a week. Soft German steel tends to roll rather than chip, so it responds well.
• Sharpening: on a stone or in a sharpener, once honing no longer brings the edge back. It removes steel, so you don't want to do it every week.

Cooks and professional sharpeners argue about rods at length (r/chefknives). They agree on one thing: a dull edge needs a stone.

A whetstone takes steel off and builds the edge again, which is why it's the real fix for a dull knife. The number is the grit: the lower it is, the coarser the stone.

• Around 1000: the sharpening grit. A dull knife gets its edge back here.
• 3000 to 6000: polishing. It finishes the edge the 1000 made, but won't sharpen a dull blade.
• Coarser than 1000: what you reach for when there's a chip to grind out.

The angle matters as much as the grit. America's Test Kitchen recommends 15 degrees for Asian-style knives and 20 for Western ones, working from the coarse side to the fine until you can feel a burr, a thin curl of steel, along the whole edge.

Soft stones like the King cut quickly, but they wear, dish, and need soaking first. Hard ones like the Shapton stay flat and don't need soaking. Both need flattening now and then.

You pull the knife through a slot or between wheels that hold it at a fixed angle. That's the appeal: a minute's work and nothing to learn. America's Test Kitchen dulled knives, sharpened them and looked at the edges under a microscope. Among manual sharpeners, diamond pull-throughs did best and rolling ones worst, because the cylinder doesn't reach the whole edge.

The catch is the fixed angle. Neither of the two here is diamond, both suit softer Western steel, and a pull-through takes off more steel than a stone does. They're for light touch-ups, not for a Japanese knife. A poster on r/chefknives put it plainly: a cheap stone and a few videos is the usual advice.

An electric sharpener is the quickest way to an edge, and the hardest one to get wrong: the guides hold the angle for you. Wirecutter tested eleven manual and electric sharpeners and chose the Chef'sChoice Trizor XV, the one here.

The price of that ease is steel. It grinds the edge to 15 degrees, which suits European and Japanese knives, but it removes more metal than a stone, so it uses up a knife faster than a stone does. For hard knives a whetstone is gentler.

It depends on the knife and how much patience you have.

• You've never sharpened: the King stone and a few videos. It forgives a beginner and teaches you the angle.
• A Japanese knife: a stone, the Shapton for one, and a ceramic rod for upkeep. Hard steel chips when twisted and is best kept up on a stone, and a 20-degree pull-through doesn't fit it.
• Done in a minute: the electric Trizor, or a pull-through for a soft German knife that only needs a touch-up.
• A German knife you just want to keep keen: the ceramic rod every week, and a stone or sharpener once it's truly dull.