Originally Posted by
niftyshaving
It turns out that the thumb nail is a lot like heavy whisker and will "catch" on a sharp
edge. Most beginners catch on a thumbnail with too much pressure and that is not good for a fine edge.
Some old timers have a very light touch and like it as a test. The thumb pad also catches and if you use more than a
light touch will cut yourself. Thus a thumb pad test is is a good test for the razor, good for your thumb... well depends
on how light a touch.
I like what I call a wild hair test.
You can use a shed bristle from an old boar brush or raid the hairbrush of a dark hair
friend.
A hair or bristle will catch on a well set bevil it will skate and slide on dull.
After a good finish hone the same hair will just fall off the edge...
I can test the entire length of a blade by touching the last 1 mm or 1/8 inch
of the hair to the edge. A two inch hair lets me touch and test a dozen + spots
from toe to heel on a razor.
If you have gray hair like me use a dark background so you can see the grey hair (or blond).
Butchers will sometimes touch their edge to a chopstick or a hard plastic rod or cutting board edge to see if it catches.
A sharp kitchen knife will catch on a common wood chopstick.
For kitchen knives... a tomato, with the peel attached, or a green apple is a good gauge.
You should be able to easily cut into the surface by directing the knife with very little pressure and slight slicing motion.
Same for green pepper, skin side up should slice as easy as skin side down. A dull knife slides and skates
on green pepper or tomato skin.