Soy retired after me. She let someone sharpen her knives after I left. In a hurry wailing away on stone screwed up the geometry in relatively short time. Asked her if I could use her knife to show how not to sharpen. This is Japanese dragon blade cherry imports sold to Cooks in Hawaii.
As I kept teaching from first class didn't know what I was doing boring them with more knowledge than they needed. To streamlined visual inputs like speed sharpening & what to do & pitfalls of bad or no technique. We are visual monkeys at least I am. Turned out quite a few accomplished freehand sharpeners.
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