If your aim is merely to make something sharp enough that it can cut, you can make a knife out of a whole lot of things. Virtually any sort of metal, to begin with, so long as you have the heat to make it malleable, tools to beat it into shape, and a stone to sharpen the edge. If you want to go further, you can dabble with beer and bacon, or old batteries.
But as Youtuber kiwami japan demonstrates, you can get much, much more extreme with a little bit of basic chemistry knowledge. Say, for instance, you need a knife that can float. Why not just go to town on some styrofoam?
Of course, styrofoam in its natural form is not suitable for useful cutlery. Instead, kiwami japan makes uses a few clever techniques to condense the air-filled polystyrene foam that styrofoam is made out of into a denser, rock-like material that can take an edge. By distilling mashed up orange peels and using the resulting orange oil to melt the foam and further treating it further in grain alcohol, our extreme knifesmith was able to remove the air bubbles that make styrofoam foam and reduce the polystyrene to a hard puck. From there, it’s just a matter of cutting out a blade shape and sharpening it.
The resultant knife can cut well for sure, but the materials we use for knives are chosen based on much more than their ability to take an edge. Chief among them is the ability to keep an edge. Despite being harder than styrofoam, polystyrene won’t be able to hold a candle to the hardness of even your softer steels, and as such would require an absurd amount of maintenance to keep in cutting shape. That, plus all the commotion it takes to make one, is why this amounts to little more than a stunt. So far as stunts goes, it’s a good one. Makes you wonder if there’s anything that can’t be made into a knife.
Originally posted on Popular Mechanics