Dulling blades on a strop

Over the last 2 months I've been experimenting. Although I doubt anyone will find much interest in this post I thought I would discuss it anyway (its a forum afterall, right?)

I've been experimenting to discover two things:

1) What is the best way to dull an edge with a strop; and

2) What are the best corrective actions afterward

Now you might be thinking, why such a stupid experiment? I can only say that once your past the whole "whats the best way to sharpen, strop, shave" type of stuff you kinda run out of experiments pretty quick, but if you read on you might find some interesting points.

I have to start by saying I limited my tools to a standard lightweight/thin high end Dovo strop, about 2 1/2 inches wide and a barber hone. I did this mostly because I completely misinterpreted the amount of damage that occurs to an edge when it gets dulled on a strop. I might have broken out a 4K had I known better.

What I have concluded is that the best way to dull an edge with a strop is by allowing sag to occur during the stropping action. This is by far more likely to cause dulling than the application of pressure while stropping on a taut strop.

Before the experiment I used to feel that too much pressure and too much sag were probably about equal culprits in the dulling of an edge.

Next, I discoved that the best corrective action is 70-90 strokes on a barber hone.

I was really shocked at the amount of work required to get the razor back up to speed. I thought, before the experiment, that I could correct the problem with better stropping, different stropping, or even say 10-20 strokes on a barber hone.

Even with light pressure and a sagging strop I created enough edge dulling to require a lot of work on the hone, more than I had ever expected.

I agree with you Alan.
The "best" way to dull a razor is light pressure on a sagging strop.
It is interesting to discover what happens with a lot of pressure (on the spine) on a sagging strop.

That's quite the study! Definitely going to have to really watch the tautness of the strop in future.

Thanks for this useful post!

Attention to detail like this saves me a lot of time on occasion, and I have suspected my early stropping to have dulled one of my razors. I do believe I will go at it on my fine stone longer than I was previously willing.

Just to be clear, Alan, when you talk about sagging, you aren't talking about a strop that is just short of taut, but is really sagging--describing a slope or making a U-shaped valley, so to speak?

I guess it makes sense, because when you are going done that slope, you aren't going parallel to the strop anymore. You are almost dragging the edge across the strop's surface--or at least that's the mental picture I get.

Thanks for doing this so others don't!

Dan

Actually a great experiment !!!!!!
I have always said a strop is a tool that either brings a keen fine edge to a razor or will wreck one faster than you would ever believe....
I will admit that I never realized how bad it could wreck one though, I would have thought the 20 strokes on a fine hone would bring it back too....
Thanks for taking the time and effort Alan

Nothing wrong with this experiment Alan.

Once we find the cause, we can eliminate the cure. And this does that exactly. I always wondered about people saying using a heavy stroke on the strop dulls the edge because I lean a fair bit on the strop (linen side). I find this gives me a better edge and can often save me having to go to the stones.

Excellent!

Yes, sir, that is correct. I am not referring to mild deflection. I have decided to go so far as to separate the concepts entirely with a different word.

This was a full on sag and a light touch, about 2 inches of sag at the middle of the strop.

I often strop with a "relaxed" strop, almost straight but not hyper taut.

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Originally Posted by dcarmell

Just to be clear, Alan, when you talk about sagging, you aren't talking about a strop that is just short of taut, but is really sagging--describing a slope or making a U-shaped valley, so to speak?

I guess it makes sense, because when you are going done that slope, you aren't going parallel to the strop anymore. You are almost dragging the edge across the strop's surface--or at least that's the mental picture I get.

Thanks for doing this so others don't!

Dan

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That is interesting. I've been wondering about pressure on the linen lately. I'll have to try that.

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Originally Posted by poona

I lean a fair bit on the strop (linen side). I find this gives me a better edge and can often save me having to go to the stones.

Excellent!

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Haha! I found out the best way to wipe an edge off with a strop almost the first time I laid razor to leather.... It's an easy three step process:

1. paste one side of strop with Dovo red paste;

2. Lay razor on pasted strop;

3. Let the strop sag, and strop away!

Beautiful dull edge in seconds :roflmao

I'm glad you did this experiment Alan - like Poona says, knowing the cause helps avoid the problem. Your post brought back traumatic and deeply suppressed memories for me, and I can now recall and totally agree with how much effort is required to fix up the edge...:fim::gth

James.

thanks for the idea of deliberately looking at ways to dull an edge, therefore providing awareness of the dangers of how to do it....

I found that rolling my edge on a strop worked quite well for me, not only did i nick the strop but buggered a shave ready edge with no way of re-sharpening it...took me a while to progress i can tell you.

A great experiment and thanks alan for the info..

regards,simon:tu

Quote:

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Originally Posted by gssixgun

Actually a great experiment !!!!!!
I have always said a strop is a tool that either brings a keen fine edge to a razor or will wreck one faster than you would ever believe....
I will admit that I never realized how bad it could wreck one though, I would have thought the 20 strokes on a fine hone would bring it back too....
Thanks for taking the time and effort Alan

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I learned it the hard way. When I first started using straight razors, I had Lynn hone my starter razor. My very first use with the razor was undermined because my poor stropping dulled the razor. I never enjoyed the honemeister sharpness. :(

A very experienced friend showed me that about 3/4" of sag is preferable to very taut. Does that agree with your experience?

As a relative newbie who just figured out how to strop correctly, this strop probably kept me from doing something stupid in my quest for even greater improvements. Nicely done.

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Originally Posted by Yannis

I agree with you Alan.
The "best" way to dull a razor is light pressure on a sagging strop.
It is interesting to discover what happens with a lot of pressure (on the spine) on a sagging strop.

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Just visualizing this, without actually testing it, increasing the pressure on the spine using a sagging strop would stretch the strop in both directions creating, essentially a taut strop. Therefore, why not start with a taut strop to begin with?


Scott

I agree that passing a razor on a sagging strop will ruin an already keen edge. It is simple geometry. If you have a taught strop it is very similar to a leather paddle strop. With the spine and edge of the blade held with uniform pressure against the leather surface the bevel should be essentially flat, in full contact with the leather. If catenary (the fifty cent word for sag) is introduced, the blade (regardless of pressure distribution) will then be describing a chord across the radius of the catenary. This will hold the bevel off the surface of the strop and force the edge to drag tangentially across the leather subsequently rolling and/or breaking the fine edge. You can do exactly the same thing with a taught strop or a paddle by lifting the spine of the razor while stropping.

No, I haven't found that to be true yet. I've been using a taut strop with a dab of pressure for years because that was the way I was taught. Lately I've been working on using no pressure (with more passes). I've been following the advice to use "only the pressure needed to attain draw", as in the barbers manuals.

I actually, just yesterday, dulled my edge slightly with very mild deflection, like 2 mm.

I'm pretty certain that there is a correlation between the strop, technique, pressure and deflection. In that many people can strop a little differently and get the best results.

I've been working on using just a feather light touch to see what I could accomplish and that has been doing well.

I haven't yet made any conclusions on what is the perfect amount of sag or that 3/4 is perfect. I haven't worked that amount of sag much but would think that would be a little too much. It is more than I've ever routinely used.

Anyone else want to chime in on this? I'd have to try it a bit to make any intelligent reply.

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Originally Posted by Slant-Fan

A very experienced friend showed me that about 3/4" of sag is preferable to very taut. Does that agree with your experience?

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Quote:

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Originally Posted by icedog

I agree that passing a razor on a sagging strop will ruin an already keen edge. It is simple geometry. If you have a taught strop it is very similar to a leather paddle strop. With the spine and edge of the blade held with uniform pressure against the leather surface the bevel should be essentially flat, in full contact with the leather. If catenary (the fifty cent word for sag) is introduced, the blade (regardless of pressure distribution) will then be describing a chord across the radius of the catenary. This will hold the bevel off the surface of the strop and force the edge to drag tangentially across the leather subsequently rolling and/or breaking the fine edge. You can do exactly the same thing with a taught strop or a paddle by lifting the spine of the razor while stropping.

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I think this is incorrect, or at least oversimplified. With even a little bit of pressure the strop loses its parabolic shape and describes more of a very shallow "V", with the strop bending to varying degrees at both the spine and the edge. The bending at the spine doesn't affect the edge at all - if all the pressure is focused on the spine and the blade just wafts behind, then all the bend in the strop is at the spine and the edge will strop normally on the straight trailing edge of the "V" - you're just using the spine to finish tensioning the strop. Similarly, even with a shallow sag you can dull a blade if you apply a torque to the blade so all the bending in the strop occurs at the edge of the blade. Of course it's easier to get everything right if you minimize the variables, which is where the "keep a taught strop and use very little pressure" rule comes from - it's easy to keep the strop taught, and easy to keep the pressure light. Or at least easier than dealing with the changing angle, pressure, and torque as you stroke across a slack strop, stropping against the straight trailing edge of a changing angle as you sweep across. It can be done - we've all seen Lynn shaving off a slack strop in his youtube video:eek: But the fact that something *can* be done a certain way is not a reason it *should* be done that way.

I always find that the key is pressure. Very light ........tis the same for honing, stropping and shaving, even though the exercises are different. Less pressure is usually mo bettah :tu

Have fun.

Lynn

A really interesting post and thanks for the experimentation.

I have found that the stiffer the blade, the tauter the hanging strop must be. The full hollow ground razor has enough flex in the blade to accommodate a slightly less taut strop.

Full wedges strop really sweetly on a strop laid on a flat surface.

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Originally Posted by mparker762

I think this is incorrect, or at least oversimplified. With even a little bit of pressure the strop loses its parabolic shape and describes more of a very shallow "V", with the strop bending to varying degrees at both the spine and the edge. The bending at the spine doesn't affect the edge at all - if all the pressure is focused on the spine and the blade just wafts behind, then all the bend in the strop is at the spine and the edge will strop normally on the straight trailing edge of the "V" - you're just using the spine to finish tensioning the strop. Similarly, even with a shallow sag you can dull a blade if you apply a torque to the blade so all the bending in the strop occurs at the edge of the blade. Of course it's easier to get everything right if you minimize the variables, which is where the "keep a taught strop and use very little pressure" rule comes from - it's easy to keep the strop taught, and easy to keep the pressure light. .

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I totaly agree!

Now let's add another dimention to this stropping thing: the path of the razor over the strop and relation to the angle of the micro-serrations at the edge.

Maybe another thread.


Scott

Interesting experiment, and thanks for taking the time and effort doing this sort of thing, Alan :). I think hese kind of experiments can be useful 'cos they come from the opposite direction we usually take. We're all naturally consumed with getting our razors sharp (and the right kind of sharp to boot), but I guess it's also a good idea to sometimes experiment with achieving the opposite results so one can have a more intuitive understanding of how the material behaves - ya know, the whole gestalt.

Leon

Quote:

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Originally Posted by mparker762

I think this is incorrect, or at least oversimplified. With even a little bit of pressure the strop loses its parabolic shape and describes more of a very shallow "V", with the strop bending to varying degrees at both the spine and the edge. The bending at the spine doesn't affect the edge at all - if all the pressure is focused on the spine and the blade just wafts behind, then all the bend in the strop is at the spine and the edge will strop normally on the straight trailing edge of the "V" - you're just using the spine to finish tensioning the strop. Similarly, even with a shallow sag you can dull a blade if you apply a torque to the blade so all the bending in the strop occurs at the edge of the blade. Of course it's easier to get everything right if you minimize the variables, which is where the "keep a taught strop and use very little pressure" rule comes from - it's easy to keep the strop taught, and easy to keep the pressure light. Or at least easier than dealing with the changing angle, pressure, and torque as you stroke across a slack strop, stropping against the straight trailing edge of a changing angle as you sweep across. It can be done - we've all seen Lynn shaving off a slack strop in his youtube video:eek: But the fact that something *can* be done a certain way is not a reason it *should* be done that way.

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How is what I wrote incorrect? I basically state that if you drag the edge of a razor across a strop with (the bevel lifted but the edge on the leather) you will damage the edge.

Whatever.