No offense, but I see absolutely no value in this type of testing. I think it borders on dangerous and you can be lucky that the "knife jumping" trick didn't take out an eye or worse.

For hundreds of years a knife and an axe (and later a rifle) were regarded as essential and life preserving tools and were therefore treated as such. Only lately they seem to have become rock crushers, brick breakers and pipe cutters. Throughout my life I have been taught, first by my father and later by the military, that your equipment is your life and should be cleaned and maintained daily and handled with care and respect and this new tendency to maim and destroy something that is meant to cut soft materials is absolutely contrary to what I have learned and what I will teach my son.

But of course, that's just my opinion. To each his own.
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