When you’re cooking in the kitchen, chop vegetables and then scrape down what is cut in the salad bowl, always make it a habit to turn the knife over and scrape with the back of the knife. If you scrape with the knife edge, the outermost foil-thin part of the knife edge is bent sideways and is clearly visible under a microscope. This is exactly the part that a sharpening steel has the task of straightening.
The sharpening steel can be completely straight and you don’t need quick movements as you often see chefs do, it’s probably more about the chef being in a hurry or wanting to impress and shine… If you scrape with the back, your kitchen knife will stay sharp much longer. If you look closely at the Disney film Ratatouille, you can’t help but be impressed by their research when you can see examples of just this routine!
If you want to care for and maintain the knife edge even more, a piece of leather with a little Autosol chrome gloss as a polish can be good to use and, like the barber, trim the knife edge when you want it extra sharp. When the knife has become too dull after use, there’s only one thing to do. Sharpen the knife. Then it’s extra important to grind cold, with lots of cooling water that removes all the frictional heat that is formed. If the edge has turned blue, the edge is tarnished and destroyed, then you must at best grind away all the destroyed metal to get into fresh steel and in the worst case replace the entire knife with a new one.
The basic rule is that if sparks are formed during grinding, the overheating is very close and at the outermost thinnest part of the knife edge there is no mass that absorbs the heat, but it instead becomes overheated quickly and the heat treatment is destroyed.