Tape and sharpness

[bart]

That's a great explanation Bart. I have never noticed the difference you speak of but to be honest, I don't put a secondary bevel using tape. I am sure what you say is correct.

The sane logic might explain how daily stropping works.

Thank you, Peter.

You wont hear me saying the a secondary bevel is supposed to be prerequisite for a good shaving edge. But the question was whether tape can add sharpness beyond what is possible without tape (given the same hone). I believe the answer to that must be affirmative.

Concerning stropping, The picture I linked in the previous post shows, especially the rightmost image, the presence of bur-like structures at the edge very well. I think it indicates the importance of a thorough first stropping session, before the edge really reveals itself. I find linen to be more effective for that first stropping session than leather, and speculate that linen therefor is more abrasive than leather. I think leather is more about burnishing the very edge, than about abrading it. Burnishing, as opposed to abrasion, depends more on the plastic deformation of the irregularities along the outer edge, caused by honing or shaving. It lends it efficiency from friction more than from abrasion.
Verhoeven happened to also compare the bur-reducing properties of clean leather against those of leather treated with chromium oxide, and found clean leather to be inefficient for that purpose. I believe he was correct with that conclusion, albeit he seemed to not realize that clean leather stropping achieves something else, that matters much for the purpose of facial shaving.

One day, with access to the proper equipment and someone to operate it, I hope we can take up the research from the point where Verhoeven's paper stopped.

Kindest regards,
Bart.

[Danricgro]

Thanks for the information Bart. When I first saw this thread I wanted to answer yes right away. I have added a layer or two of tape many times on several different finishing stones to help with that last bit of sharpness I was looking for.

I hesitated because I have nowhere near the experience most of the others here seem to have. The fact is that in my limited experience adding a layer of tape for the last few strokes on a finishing hone has worked every time I have tried it.

For what it is worth the stones I have tried it on are Coticules, Jnat, Thuringian, Naniwa 12k SS (gotta be careful, likes to chip the edge) and a Surgical Black Arkansas. It has been successful on all of them.

[Rtedwards]

I fully agree with Bart. For about a year now I have been playing with secondary bevels on bevels of different angles. I don't always get a measurable increase in sharpness from the secondary bevel as measured with the HHT, but a tiny secondary bevel always seems to make the shave smoother regardless.

Just to be clear, this is not the Unicot technique. This is putting the tiniest secondary bevel on an edge that has already reached at least HHT3 with a dilucot. I use one layer of tape (now I'll have to try two after reading Bart's post) and maybe 10 very light strokes on water alone. Twenty if I am using a thuringian instead of a coticule. Too many strokes and you seem to be back where you started.

I've been pondering Bart's explanation for my empirical observations, and think it makes sense. I had been thinking that I was just cleaning some of the irregularities from the edge of the edge, but Bart's mechanism would explain why too many strokes on the secondary bevel eliminate the advantage, as you do more the tiny bevel widens and your equilibrium point goes back to a larger radius.

The secondary bevel doesn't seem to improve edges with large initial bevel angles regardless of bevel width. Starting at around 18 degrees the secondary bevel just doesn't seem to work and even seems to increase the shaving resistance sometimes.

At any rate, I am a fan and this is how I finish every razor I own now except for the ones 18 degrees and above, which isn't many.

[bart]

Ah. Angles. My favorite hobbyhorse.

I still don't get why so many shaving forums are filled with endless talk about chromium oxide, cubic boron nitride, finishing stones X, Y and Z, but as soon as the topic of bevel angle is brought up, it becomes strikingly silent.

It is odd, because angle differences, by my experience, can have a greater influence on how a razor shaves than different types of "finishes". It is even quite possible that some of what I'd call "ultra-finshers" (0.3 micron particle size and even well below that) require a secondary bevel at considerably widened angle, in order to truly reveal their best properties.

Kind regards,
Bart.

[Matt]

One important factor, I have left unmentioned to this point is: bevel width.
(…)
While the abrasion at the bevel shows drastic changes between wide and narrow bevels, the detrimental forces on the tip during impact stays fairly constant.

As a result, wide bevels reach a different "maxed out" radius than narrow bevels, because their slower bevel abrasion per stroke reaches the point earlier where it cannot make up for the tip detriment per stroke.

Interesting, I have re-read your post yet again, Bart. Until now I've been under the impression, that it's only easier to max out the edge by creating a secondary bevel, and a skilled honer can get the same result without it. If I recall correctly, this is what had always been said about Dilucot / Unicot — the former can be as good as the latter, with practice. So it's not exactly true, starting from certain bevel width, or I am missing something here?

I'm not undermining anything, I'm genuinely surprised.

Bevel angles! Do we have a candidate for the next experiment, then? :)

regards,
Matt

[tat2Ralfy]

Oh this could get dirty
I don't want to get into bevel angles and experiments, but I will say that I have played around with some tape in my time, and must agree that it makes a big difference to me, I know Gary tried some variations as well and got the same results
Keeping a bevel angle as close to 18 degrees (iirc) definitely made for a nicer shave

[bart]

Interesting, I have re-read your post yet again, Bart. Until now I've been under the impression, that it's only easier to max out the edge by creating a secondary bevel, and a skilled honer can get the same result without it. If I recall correctly, this is what had always been said about Dilucot / Unicot — the former can be as good as the latter, with practice. So it's not exactly true, starting from certain bevel width, or I am missing something here?

No, you are not missing anything, Matt. Though I don't doubt that my observations and the hypothesis that sprouts from them would be considered highly controversial among many straight razor users.
A lot of people consider the use of tape as a sort of "guiding wheels" for the inept honer, "cheating" your way to sharpness, anachronistic and "in the long run detrimental" to the Holy Intentions of the Razor Manufacturer.
For these reasons, the mere thought that tape could actually accomplish things that can't be accomplished with traditional honing, is appalling.
But it is not about tape. It's about angles and secondary bevels. Tape is just one means to get there.
One could create a hone with a concave surface to achieve secondary bevels as well. Or do the opposite: set bevel on a convex stone, finish on a flat one. Check this out: http://www.coticule.be/the-cafeteria/topic/518.html. Or Jarrod's (kiwibogcity) contribution on this very forum about a bit of edge exotica performed by Thiers Issard.

But where was I?
Yes, tape. The easiest means to fool around with advanced bevel variations. Give me any Dilucot edge and I will make it sharper by "unicotting" it. That does not mean you'll like it better. Not every face likes sharpness. I still argue that The Edge Perfect is the edge that shaves with the least possible effort to sever whiskers BUT NOT separate skin cells. Sharpening razors, in my mind, is not the puberal sharpness race that some make of it. The Edge Perfect is different for every face, every hand that wields the razor, every beard. If we learned something from the BBW experiment, it has to include that edges that made some of the research team lyric, did not work for other members of the same team.
Imagine that I'm in the habit of maintaining a shaving angle of 5 degrees in relation to my skin, while you keep it at 20 degrees. We would definetely require different edge characteristics. And then we haven't even discussed skin differences...

But yes, if we speak of bare keenness. A narrow secondary bevel can be made keener than a wide single bevel. That is my experience with a number of solid hones (all natural rocks except one synthetic).

Even during the Cafeteria days on CBE, I made a number of (somewhat ignored) posts exploring those observations and my explanation for them. Here's one of those:http://www.coticule.be/the-cafeteria/message/25550.html

Kind regards,
Bart.

[asharperrazor]

What's really funny is that people used to think that honing the razor flat on the spine was cheating back in the day.

Now tape is cheating? What next? Laser guides? Lol. Okay I'm being facetious with the lasers.

[Tom]

A very interesting thread!

I agree with the idea of the larger surface area on the bevel requiring more time to hone, and by turning up the blade with a layer of tape or two, it allows the edge of the edge (is what I call it) to be more fully and cleanly abraded. The raised angle also allows the apex of the edge to come closer together.

However, increasing the angle also increases rigidity of the edge, which is good for some razors, but may not so nice when dealing with others. Tape is sometimes required simply because of warped spines, but is also good for steel that gets too thin and rolls (newer Solingen blades are most prone to this in my experience).