This Crazy Knife Is Made By Shaving a Piece of Fish

This ingenious blade maker creates a knife form the world's hardest food, a Japanese dried fish called "Katsuobushi".
Jessica Miley

Blade and knife enthusiasts will know that YouTube is full of demonstrative videos showing how you can make a knife from a variety of weird and wonderful things from old batteries to chains. But what about making a blade from fish? Sounds crazy but one inventive blade maker did just that, taking a slab of Katsuobushi or fermented and smoked fish and shaving it down into a usable cutting device. 

Katsuobushi holds the title as the hardest food on earth and it looks a lot like a lump of old wood. The unusual foodstuff is a key ingredient in many Japanese meals. It is also known as bonito flakes. It’s likely you have had it if you have ever enjoyed a Miso soup a dashi-based dish or had the flakes on top of noodles or sushi. The fish knife was made by shaving and shaving a chunk of Katsuobushi down until an edge was formed. We hope they kept the shavings for dinner. Katsuobushi is made with a long and complicated process. It starts with fresh fillets of Katsuwonus pelamis or Skipjack tuna. The fatty belly parts are trimmed away and the lean fillets are simmered in water for around an hour. The fillets are then smoked using Oak, Pasania, or Castanopsis wood. They are smoked for 5-6 hours, then left to rest for a day, then smoked again. This pattern is repeated 12-15 times. The final stage is the sun drying and fermentation using Aspergillus glaucus culture. At the end of this two-week process, the fillets of fish are less than 20% of their original weight.