Thread: Thumb test -- how does it work?

Forum member Randydance suggested to me to take a new DE or SE blade and practice the TPT on that. This worked very well for me. YMMV. I don't know why it is suggested to moisten the thumb with the TPT or the thumb nail with the TNT but I suspect it is to lubricate the surface. Less chance of a false positive ? In the barber manual excerpt it specifically says not to use saliva. There may be corrosive properties in it that could damage the edge if it were not completely removed.

I saw that. I could have sworn you run your thumb along the blade. Whatever, it worked for me. It was just a very gentle slide along the blade.

Originally Posted by ziggy925

Well, I kinda understand. I'm running my thumb along the blade, not plucking against it. All the videos show running your thumb "along" the edge. Still, I don't see any damage to my thumb. Maybe I'll have to dig out my scope.

Explain why I have to lick my thumb? What does the moisture do?

Moisture softens and swells the cuticle (corneal layer of skin) - easier for the edge to cut and less damage to the edge. Also the moistened skin is a bit more sensitive to touch allowing better perception of keenness.

Saliva was a no-no in barbershops because, well because it's bad form to spit on tools that will be used on customers. Ewww.

Originally Posted by Bart

Yes, I am aware of that.

I was really hoping for an explanation as to why it is different. If it is wrong (not being a jerk, but your post read authoritatively), why hasn't one of the more experienced members corrected the Wiki? Not being argumentative, just want to know.

I just read the Wiki article on the topic. The words across and along may be confusing to some folks. When I do the test it is from the heel to the point and at no time do I move my thumb from one side of the edge to the other ....i.e. across. I don't know if that is right wrong or indifferent but it is the way I do it. There is the right way, the wrong way and than there is my way.

Originally Posted by JimmyHAD

I just read the Wiki article on the topic. The words across and along may be confusing to some folks. When I do the test it is from the heel to the point and at no time do I move my thumb from one side of the edge to the other ....i.e. across. I don't know if that is right wrong or indifferent but it is the way I do it. There is the right way, the wrong way and than there is my way.

From the Wiki:

Performing The Test


Thumb Pad Test
Hold the razor in your dominant hand and aim the edge upward.
Place the fingers of your off hand along the downward facing spine for absolute control over how your thumb contacts the shaving edge.
With a moistened thumb pad, draw your thumb very gingerly across, not along, the edge repeating all along its length to feel how it grips or bites into your thumb print.

Then there is a picture to the right showing the holding position and an arrow pointing showing illustrating the direction.

Here's an explaination I found at Badger and Blade:

"One test I really like is the thumbpad test. Took a long time to use it and understand it but it evaluates whether a razor is shave ready, NOT sharp. The razor is honed and then stropped EFFECTIVELY and if both occur the wet thumb pad (wetted for atleast 20 seconds) actually sticks to the edge instead of sliding if you GENTLY move your thumb over the blade lengthwise, yes, lengthwise. What happens is the edge digs into the skin of the first layer of your thumbpad. For you squimish types you can just bound your thumb pad on the blade and you will cut the first layer of skin with the edge. This is only visible with bright light."

I think the wiki here is confusing. I've seen people go "across" the blade checking a knife, but never a razor.

Have to give credit to AFDavis11 over there.

Yeah, It sounds like the wording in the Wiki is just a bit messed up...maybe it should say "from heel to toe" or perhaps "parallel to the cutting edge, not perpendicular to it."

It is certainly confusing to be sure. Maybe someone should edit the Wiki article...*hinthint*

*EDIT* also noticed the picture...yeah, don't do that...I don't know why someone hasn't changed it by now, but you don't want to "pluck" the edge of your razor like the picture and text indicates.

Come on moderators or ppl that can edit, let's change it to the right way

Originally Posted by avatar1999

Yeah, It sounds like the wording in the Wiki is just a bit messed up...maybe it should say "from heel to toe" or perhaps "parallel to the cutting edge, not perpendicular to it."

It is certainly confusing to be sure. Maybe I will edit it, unless someone beats me to it.

English is not the original author's first language if I am not mistaken. I think he meant to say to go along the edge from heel to point .... not across or from one side to the other ... but I will leave it to someone else to edit the article. I don't want to put words in someone else's mouth and then quote them.

Originally Posted by JimmyHAD

English is not the original author's first language if I am not mistaken. I think he meant to say to go along the edge from heel to point .... not across or from one side to the other ... but I will leave it to someone else to edit the article. I don't want to put words in someone else's mouth and then quote them.

I certainly hope someone changes it. Not saying the original poster did it intentionally, but it SHOULD be corrected, since from my understanding, no one checks the edge by "plucking it" (e.g. side to side) like was pictured and stated in the Wiki article.

Thought that's why it was editable...so we could correct mistakes *shrug*

I would do it, but I don't have the authority to edit