Thread: Dulling blades on a strop

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

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

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.

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.

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.

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?

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.

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 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

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.