Kitchen knives dull over time because the thin cutting edge bends and rolls with repeated use.

The longer version

A knife edge is only a few micrometers across, so the metal there is thin enough to deform under the stresses of cutting. Repeated contact with a board and with hard food rolls the edge to one side or folds it into a burr, and microscopic chips break away where the steel is brittle.

Even when no material is lost, a rolled edge no longer meets the food cleanly and feels blunt. Harder steels resist deformation better but chip more readily, so blade geometry is a compromise. Honing realigns the edge, while abrasive sharpening removes metal to form a new one.

Where this entry sits

Everyday ingredients turn out to be full of quiet chemistry and long history. This collection gathers short, plain explanations of how bread rises, why onions sting, where common spices originate, and how coffee, tea, and chocolate reached the modern kitchen. The full list sits on the Food and Drink page, where every entry is listed in order.