A theory of how the WE diamond pastes work

[Fred Hermann]

So after my head was done pounding reading this, following all the associated links, and marveling at the pretty pictures…one thing stands out.

Clay, how much pressure are you using when stropping? I *have* to assume you use equal pressure thru the process, but how much? I saw mention of lifting the base edge when stropping, which implies lots of pressure….

[Phil Pasteur]

I guess I was trying to hint at the same question. Considering the repeated advice given all over this forum to use very light strokes when stropping…indeed with all of the stones, I wonder how many are lifting their bases when stropping… and if not, if anyone would be seeing similar results to what Clay has seen… whether these results are the result of true burnishing or not..
??

Phil

[Mark76]

I guess I was trying to hint at the same question. Considering the repeated advice given all over this forum to use very light strokes when stropping…indeed with all of the stones, I wonder how many are lifting their bases when stropping… and if not, if anyone would be seeing similar results to what Clay has seen… whether these results are the result of true burnishing or not..

Just a brief quote from Clay:

I removed the sample and cleaned it well, the completed 5 strokes per side with firm pressure using .75um CBN on cow leather.

I don’t know whether you’ve read the posts on my blog regarding stropping, but in some experiments I did over 500 stropping movements per side. That is a lot :cheer: , and in order to see effect more quickly I used quite a bit of pressure.

My pictures are not nearly as good as Clay’s, but my conclusion was definitely that burnishing occurs, and that the WE pastes excel at doing this. That’s why I started this threat 😉 . You can read all of my posts on stropping here[/url] .

That is not to say that the common knowledge that you have to strop lightly is a myth. I don’t know exactly where the idea of stropping originated, but it has been widely used in the straight razor world for over a 100 years. If you use too much pressure on a straight razor, with an edge that usually has an acute angle and is very thin, you simply destroy the edge. Also, if you strop just to remove a burr (which is not necessary when you’re using a WEPS), you don’t need much pressure. And if you’re stropping free-hand, a mistake is made easily if you use pressure, so you’d better be safe than sorry.

Even with a WEPS, if you use a lot of pressure with a leather strop and don’t adjust the angle, you will round the edge. So setting back the angle (with leather I do 1 or 2 degrees) is necessary if you use a little force.

Molecule Polishing: my blog about sharpening with the Wicked Edge

[wickededge]

In my normal sharpening, I don’t use much pressure when stropping. When I’m going for serious polish though, I use pressure at a lower angle at first and then lighten up as I get ready to finish.

The thing about lifting the base – I’m not necessarily trying to lift the base, but once my strops are well seasoned, they have enough grip that I have to try not to lift the base and have to lessen the pressure.

-Clay

[Phil Pasteur]

I removed the sample and cleaned it well, the completed 5 strokes per side with firm pressure using .75um CBN on cow leather.

I would never have intrepreted “Firm” to mean so much pressure that he was lifting the base on each stroke.

I don’t know whether you’ve read the posts on my blog regarding stropping, but in some experiments I did over 500 stropping movements per side. That is a lot :cheer: , and in order to see effect more quickly I used quite a bit of pressure.

I did and I commented on them previously.

My pictures are not nearly as good as Clay’s, but my conclusion was definitely that burnishing occurs, and that the WE pastes excel at doing this. That’s why I started this threat 😉 . You can read all of my posts on stropping here[/url] .

I think that sometimes we can start out doing an experiment with a preconception. The results will always tend to confirm that idea if we are not very careful. It is easy to just intrpret the results in a manner that confirms the theories we have going in.

I don’t think you can see evidence of the kind of burnishing that Clay is talking about with 400X. This is why he wants to get time on an SEM to verify his theory.

That is not to say that the common knowledge that you have to strop lightly is a myth. …
Even with a WEPS, if you use a lot of pressure with a leather strop and don’t adjust the angle, you will round the edge. So setting back the angle (with leather I do 1 or 2 degrees) is necessary if you use a little force.

I will look for the thread. I distintly remember Clay suggesting that just a few light strokes with leather would make a significant improvement at the edge. I think this may have been mentioned a few times actually. The suggestion was clearly that we did not need to do 500 strokes while lifting the base to get an improvement.

The point was not whether stropping with a light touch is a good idea, which I think in general that it is. The point was, if the majority of people do it this way, with any practical number of strokes, they would likely not see the effects that we are discussing.

Phil

[wickededge]

I circled some spots on the images so we’d have some things to compare. Here is the blade after the 50# diamond plates:

and here it is after 5 strokes with the .75um strops:

In the green circle and to some extent in the fuchsia ellipses, you can clearly see signs of abrasion from the .75um CBN. In the red and aqua circles, it looks like the metal has been dragged around a little bit. It has an almost liquid appearance as though it had flowed.

I don’t have the background to speak to this, but I wonder, as Phil has voiced, if there is enough local pressure to move these delicate structures and deform them. I measured the little elongated structure in the red circle (after being stropped) to be 1.6um, which is very tiny. How many pounds per square inch would be needed to get something that small to flow? Even more to the point, can the leather grab surface molecules and shift them, like buttering bread? The next round of testing should be interesting. I’ll try it with alcohol moistened strops with no abrasive other than the grain of the leather. Once the plain paste comes in, I’ll try to duplicate the level of stiction I’m getting and test that way too, maybe on kangaroo.

Attachments:

• 50-Grit-Detailed.jpg
• 75-CBN-after-50-Grit-Detailed.jpg

-Clay

[cbwx34]

I never thought I’d see “fuchsia” in a sharpening forum…. 🙂

Maybe someone who’s a member of an engineering forum could post these pics and solicit some responses there?

I also had another thought along with trying plain leather would be to try balsa plain and/or loaded… see what that shows.

[Chris]

I never thought I’d see “fuchsia” in a sharpening forum…. 🙂

Me either, but it seems to work well.

[wickededge]

Okay, more photos raising more questions. First the 50# sample followed by the strops with no abrasives:

now plain cow leather, moistened with alcohol:

and then plain kangaroo leather, moistened with alcohol:

Next I’ll post some pictures after using strops with some abrasives.

Attachments:

• 50-Grit-2.jpg
• Plain-Leather-1—5-strokes.jpg
• Plain-Roo-Leather-1—10-strokes.jpg

-Clay

[wickededge]

First off is .125 CBN on Nano-Cloth:

now 3.5um Diamond on Balsa, moistened with alcohol – 5 strokes:

and then 3.5um Diamond on Leather, moistened with alcohol – 5 strokes:

Clearly there is plenty of abrasion going on with the 3.5um diamonds.

Attachments:

• 125-CBN-on-Nano—10-Strokes.jpg
• 3.5-Diamond-on-Balsa—5-Strokes.jpg
• 3.5-Diamond-on-Leather—5-Strokes.jpg

-Clay

[wickededge]

There was absolutely no ‘stiction’ going on with the plain leather. It was just gliding smoothly over the metal. I think I’m somewhat stuck here until the plain paste arrives and I can do some true apples to apples comparisons. I’m thinking of .5um diamond paste on leather vs. .5um diamond on balsa vs. plain paste on leather vs. plain paste on balsa. .5um is visible in the scope but shouldn’t be so abrasive as to immediately obliterate the sample like the 3.5um does.

-Clay

[wickededge]

For grins, I completed 60 strokes with the 3.5um Diamond on Cow Leather:

The one thing I have learned is how to get back to the same spot on the sample in the microscope’s field of view 🙂

Attachments:

• 3.5-Diamond-on-Leather–60-Strokes.jpg

-Clay

[wickededge]

Here’s a close up:

The big gouge measures 38um x 12.5um.

If we keep this up, we’re going to have to start naming features like astronomers do on the moon and planets.

Attachments:

• 3.5-Diamond-on-Leather–60-Strokes-Zoomed.jpg

-Clay

[Phil Pasteur]

Hey Clay,
Interesting ..I was going to try to circle those aqua areas myself.
That small feature looks like it may have been a thin flap in the 50 grit photo, cut by the diamonds. Being as this as it is, it looks like it got sort of folded over and moved a bit and flattened. This might not take much force. After all the piece is probably not as thick as a piece of aluminum foil.

One thing to remember as well. There is a grit distribution in any compound. There are probably abrasive particles in the 0.75 micron compound that range from at least 0.25 to maybe 1.5 microns. These varying sized grits could also be contributing to the smoothing at a level finer than what we can resolve even at this magnification.

Some of the other features definitely look like perhaps they may have been changed by abrasion, albeit very fine abrasion.

The fushia area on the second photo looks like metal has been removed… and smoothed. Perhaps again, abrasion.

I found it very interesting that the blank leather strops had virtually no effect at all. The Kangaroo seemed to make more of a change. This runs a bit counter to what we have seen where “roo strops seem to not contribute to the process much at all when used with abrasives. ???

This is very interesting. I wish I had more experience at interpreting features and their causes at this level of magnification.

Phil

I circled some spots on the images so we’d have some things to compare. Here is the blade after the 50# diamond plates:

and here it is after 5 strokes with the .75um strops:

In the green circle and to some extent in the fuchsia ellipses, you can clearly see signs of abrasion from the .75um CBN. In the red and aqua circles, it looks like the metal has been dragged around a little bit. It has an almost liquid appearance as though it had flowed.

I don’t have the background to speak to this, but I wonder, as Phil has voiced, if there is enough local pressure to move these delicate structures and deform them. I measured the little elongated structure in the red circle (after being stropped) to be 1.6um, which is very tiny. How many pounds per square inch would be needed to get something that small to flow? Even more to the point, can the leather grab surface molecules and shift them, like buttering bread? The next round of testing should be interesting. I’ll try it with alcohol moistened strops with no abrasive other than the grain of the leather. Once the plain paste comes in, I’ll try to duplicate the level of stiction I’m getting and test that way too, maybe on kangaroo.

[Mark76]

There was absolutely no ‘stiction’ going on with the plain leather. It was just gliding smoothly over the metal. I think I’m somewhat stuck here until the plain paste arrives and I can do some true apples to apples comparisons. I’m thinking of .5um diamond paste on leather vs. .5um diamond on balsa vs. plain paste on leather vs. plain paste on balsa. .5um is visible in the scope but shouldn’t be so abrasive as to immediately obliterate the sample like the 3.5um does.

This is a very interesting result. I already knew that loaded strops (both leather and balsa) can be quite effective, but I also thought that plain leather would have some effect. But apparently leather does very little by itself. This makes me wonder why stropping on plain leather is often seen as effective, particularly when doing straight razors. Is it only a matter of straightening the edge?

I recall a blog by Michiel (on belgiansharpening) where he showed that plain horse leather does have an abrasive effect. If I recall it correctly, he explained that this is due to the silicates embedded in the horse leather. And I think that some of your pictures at 200x also showed that plain leather had some abrasive effect (but maybe this was distortion due to the lower magnification).

Molecule Polishing: my blog about sharpening with the Wicked Edge

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