About Sharpening of Kitchen Knives

Knife Sharpening

Even with the hardest steel and the best edge retention, every knife will eventually lose its sharpness. There are several simple ways to check if your knife is still sharp, such as the paper cutting test or the tomato cutting test. If your knife can no longer cut through paper cleanly or slice through the skin of a tomato, it’s time for sharpening.

Many users mistakenly accept that their knives will stay dull and assume it’s difficult to maintain sharpness. But that’s simply not true. Keeping your knives sharp and performing at a tomato-cutting level is easy with a regular sharpening routine and the right tools.

Cutting with a sharp knife is not only more efficient but much more enjoyable. The difference between a dull and sharp knife can be demonstrated using the BESS scale, which measures sharpness by the amount of pressure (in grams) needed to cut through standardized test media. In this test, a common butter knife scores around 2000, a knife with a moderately worn edge 1000, and one with a slightly worn edge 500. In contrast, a knife sharpened by a skilled person using a whetstone can score as low as 50 grams, meaning it requires just a fraction of the force needed to cut compared to a duller blade.

The type of sharpening you choose depends on the condition of your cutting edge.

Edge repair and restoration: for damaged or chipped edges

This becomes necessary when the blade hasn’t been sharpened for a long period of time and when it has been abused by cutting through hard objects or used for tasks other than cutting food.
It requires removing larger amounts of material (thus reducing the height of the blade), to again obtain a straight and pointed edge again without chips.
This process is called edge repair or restoration

drawing chipped edge sharpening repair to pointed tip

Edge sharpening: for rounded edges

This is necessary when the blade hasn’t been sharpened for a longer period of time and the cutting edge has been worn by abrasion, so that it’s no longer pointed.
It requires removing material from the sides of the edge, thus producing a new, pointed edge.
The amount of material to be removed depends on how round the edge has become.

drawing round worn edge sharpening to pointed tip

Edge maintenance and stropping: for rolled or bent edges

This is needed when the edge is still sharp and pointed, but has been rolled or bent, e.g. by cutting on a hard surface with some force.
This can happen immediately after sharpening. It means that your pointed edge is still there, but is just misaligned. If so, it will not hit the food in the correct 90° angle, causing the knife to feel dull.
To restore the sharpness, material removal is unnecessary. Instead, the goal is to straighten and realign the edge

drawing rolled bent edge realign by stropping

How to repair, sharpen or maintain the edge of a knife and which devices to use is explained on the following pages: