I have an alternative approach to trying to control the materials. Obviously, you want to control the materials as much as possible. So, if you want to do some test with a carefully-chosen material, that's fine by me. However, cutting natural materials means you run into things that aren't controlled -- and in some ways, that's the whole point. Finding out what happens when I run into a particularly dirty piece of carpet, or particularly dry piece of wood, or whatever -- this is where a lot of the learning and surprises happen.
So, what do I do to control things in this case? Well, I never test one knife by itself. I'll go a step further and say that if you test a knife by itself, you're getting results that are extremely difficult -- to the point of being useless for most people -- to interpret. Someone experienced enough can interpret the results, but I still don't like it. Here's a quick example: I test a knife on a particular type of manilla rope, and it makes 300 cuts before it won't slice paper anymore. Is that good? Bad? Mediocre? Who knows -- I certainly don't. But, if you always test your knives against a couple of other "benchmark" knives, all of a sudden that result has meaning. If I test all my folders against a well-regarded benchmark like a Spyderco endura, and the endura does 250 cuts before it won't slice paper, and the new test knife does 300 cuts, well, now I know the test knife holds an edge pretty damn good.
So, my cardinal testing rule: always test your new knife-under-test with a benchmark knife or two. Try to use the same type of benchmark knife throughout your testing, through the months and years. That will give you a way to compare knives from multiple tests, even if other variables have changed. And other variables will change, including your skill at making particular types of cuts. But because you always test against a benchmark knife, the results of the benchmark knife go up also, so you still have at least a finger-to-the-wind basis by which to compare knives.
Joe
