Quote Originally Posted by honedright
I just opened up a used disposable razor and tried the "test". There is a smooth feeling, but also the sensation of the blade cutting in. That is what the test is testing for, a smooth "cutting in" sensation, or "sticky" feeling. You do need to apply a little pressure, but not much, just the weight of your thumb or finger is enough. You should also slightly moisten the skin first.
I just tried a fresh single edged razor, and I noticed it's very difficult to touch it head on. Every touch produced a slight sideways motion and grabbing or drawing of the thumb. I never noticed this with a str8 blade because of it's size and weight. Could that be what the later manual is talking about? A soft downrard touch without intentional sideways movement nevertheless catches the edge sideways and you feel a pull or drawing on the thumb. It could even be described as stickiness because it resists pulling the thumb away.

If I place the thumb on the edge, I can drawi it lightly and it feels perfectly smooth, not sticky in any way. Also, I don't feel the thinness of the edge like I do with sideways movement.

You know, this smooth cutting is starting to sound like the feeling of the thumbnail test. And then the roughness is like what you feel with a wire edge or a coarse edge. My understanding was always that the thumb test is the opposite: smooth is bad and pulling is good.