The honest answer: whenever the knife tells you it's time. You don't need a calendar or a gauge for that, just a tomato and a sheet of paper.
The tomato test
Rest the blade on a ripe tomato and pull without pressure. A sharp knife bites into the skin right away and cuts. If it slides off, or you have to press, it's time. Another check: a sheet of paper should part in one clean pull, with no tearing and no snagging.
A rule of thumb
- Home kitchen: have them sharpened professionally once or twice a year, depending on how much you cook.
- Restaurants and butchers: roughly every four to eight weeks, sooner with heavy daily use.
Honing steel and ceramic rod: maintenance, not sharpening
A honing steel or ceramic rod realigns the edge, which rolls over very slightly with use. That stretches the time between sharpenings considerably. But it doesn't replace sharpening, because it removes almost no material. Once the edge is truly dull, only a fresh grind helps.
What dulls knives fastest
- Cutting boards made of glass, stone or ceramic. Wood and soft plastic are the better surface.
- The dishwasher: heat, detergent and knocking against other items wear the edge down.
- The cutlery drawer without protection. A magnetic strip, a knife block or blade guards protect the edge.
By the way, a well-sharpened knife is safer than a dull one: it follows the cut instead of slipping.
Where to take them
You can drop your knives at my market stall in Bleckede or Scharnebeck and collect them on the next market day. Prices are on the Sharpening page, and for any question just use the contact form.