Thread: Explaining the thumb test

I think we're making a very simple proceedure into a complex subject. The thumb test is just a matter of running a your thumb pad at an oblique angle to the blade. The way you hold the razor is immaterial. As you run you thumb over the edge you will feel a roughness and thats good. If its smooth its not good. Its as simple as that.

This is one method. You can also modify the angle from 90 to 45.

As has been mentioned you can also run your thumb "along" the length of the edge, very lightly. I use both the 45 degree and along the edge.


[quote=joshearl][quote=mparker762]I think the traditional thumb test is lightly dragging your thumb at right angles to the blade (not parallel or you'll get cut). A sharp edge will kind of catch as your thumb goes across it.

So if I'm reading this right, I should do the following:

1. Lay the razor on its spine, edge pointing up.

2. Wet my thumb.

3. Drag the pad of my thumb across the edge at a 90-degree angle to the edge and a 90-degree angle to the blade. Like this cutaway view:

-----------------> (motion of thumb)
| (edge)
|
||
||| (spine)


Sorry for the bad ASCI art. It's my first attempt.

Thanks,
Josh

Originally Posted by randydance062449

you can also run your thumb "along" the length of the edge, very lightly.

OK Randy, I haven't gotten an answer on this. When you move along the edge, what do you feel? How could the edge drag anything in its sharp direction?

On the basis of this thread, I've been playing with a fresh single edge razor blade. I feel absolutlety nothing if I just touch it head on, and if I move gently along the edge, it feels perfectly smooth (I'm concerned about applying pressure). Please tell us exactly what you experience.

I've been told that the barber manual supposedly teaches this method. Not by a long shot. If it says anything it says touch down on the edge, and then it's supposed to stick or you're supposed to feel a "draw." What is that? When I put my thumb straight down on the edge, nothing sticks, ever, it just touches the edge and comes away.

The only time I feel anything is when there's a sideways component of the movement of the thumb. Then, a dull razor just slides across, and a keen one grabs it and moves with it.

I haven't heard anyone else say anything like this, but since I was a kid I had seen an old time barber do this test many times. Of course, I couldn't see any thumb movement. But when I was close enough (my eyes were a lot better then) I did see the blade jump sideways.

If you don't have an answer (or anyone else), I might just try to contact that master barber that did the CD. My barber has been deaad a long time.