Why use honing compoound?

[grepper]

Are we therefore to imply that the author also tested, and was unable to remove the burr with a dry strop?

[Jan]

Strictly speaking it was not a dry stropping.

The author was not able to eliminate the burr of carbon steel straight razor. After 100 laps on leather sprayed with 0.25 micron mono-diamond the burr was reduced to a nanoscale thickness of some 20 nm.

   

Because this foil-burr was fragile, it was broken off during first razor’s usage. He claimed that the resultant edge width was suitable for comfortable shaving.
 
Jan

[Mark Reich]

Grepper, I use the 80u CBN like I would use a 220 grit belt. Basically as a setup for finishing, one application of CBN lasts at least twice as long as a regular 220 grit belt, while leaving a cleaner edge.

I can do without the huge swing in performance from a new belt to a dead belt. The CBN works much more consistently. It's not a huge difference, but even a slight gain is nice when you're sharpening your butt off.

I like to experiment, and I'm not afraid to take chances. While it seems like the world is stuck on ridiculously fine compounds, nobody knows how super coarse compound works.

I figure it's worth the price of admission, but I don't expect anyone else to try it.

[grepper]

That’s very interesting Mark.
 
I’ve look around for CBN belts and have not been able to find any.  I wonder why?
 
So what linen belt do you use for the 80u CBN compound?  What weight?  Can you point me to one?
 
Can you really get an even grit distribution applying compound, better than say 220 grit bonded abrasive ceramic belt?
 
I would think that because the abrasive is not really fixed to the surface when using compound, that it would be less effective than a bonded abrasive belt.  It sounds like you are finding differently.

Are you really saying that just smearing on emulsion like this  works better than a bonded abrasive belt?
https://www.youtube.com/watch?v=IxJMSHR907s

I'm always willing to try/learn something new.

[pjwoolw]

The lowest grit CBN I've used is the 30 micron emulsion. It is very effective on a linen belt. I've been using the same belt for over two years. I don't use it daily but considering I go through three of four 600 grit silicon carbide belts a week it can be cheaper in the long run. The paste form of CBN , which is the product Mark favors IIRC, I haven't tried as yet. The belts can be sourced from Ken Schwartz, along with the compounds, or the Klingspor woodworking shop.

[grepper]

Well Pete, that makes sense.  For me at least, it’s one of the few reasons that I can think of that is a good reason explaining the use of compounds.  The backing material of the belt is reusable, and it’s less expensive in the long run to just resurface the belt than to purchase a new one.  I also can see how it would be very handy if you forgot to reorder and you need a quick belt.  Just squirt on more goo and you’re good to go!  The only other advantage that I can think of is if the abrasive grit size in not available in the abrasive backing material needed for a particular application.
 
Like everybody else, I have used compounds and have at least some understanding of what they do.  That experience led me to start this thread with the very open ended question, why use honing compound, because of the extraordinary popularity and variety of the stuff, as well as the dedication of its aficionados and the alacrity with which its benefits are proclaimed.  In some threads it almost seems elevated to an almost mystical status of being some sort of secret special sauce. 
 
Sadly, my personal experience did not ignite such excitement.  To me the stuff seems to be just another, generally very fine grit polishing compound, and if anything less effective than commercially available bonded abrasives.   But the popularity and veritable cornucopia of compounds gave me pause to consider it further.
 
Please bear with me for a couple of paragraphs because what I am trying to understand requires a bit of explanation.  For this I’m only concerned with abrasive belts, sandpaper or abrasive pads and not stones or grinding wheels, etc.  I’m also not addressing the durability of the abrasive, such as AO vs diamond, etc.  For simplicity, let’s just consider belts.
 
Modern manufacturing produces high quality abrasive belts for an incredibly low cost.  It’s really pretty cool when you think about it.  Belts are available from really gnarly 24 grit ceramics to 3 micron, which is something like 8,000 grit, fine finishing belts. 
 
So, what makes a good abrasive belt?  Here’s my take on it:
 

1. Strength and stability of the backing material.  A belt is pretty much junk if it shreds, tears, breaks or has weak areas that makes holes in the belt, or is not strong enough to hold the bonded abrasive material.
   
2. Consistency of the abrasive particle size.  Obviously if you have a 200 grit belt, that’s about what it should be within reason. 
   
3. Well bonded abrasive particles.  Nobody wants a belt that gets bald spots!
   
4. Consistent abrasive particle distribution on the surface.  It would be odd to have a belt with dense abrasives on some areas and sparse abrasives on others. 
   

 
So, how does this correlate to applying honing/abrasive compound to a leather or linen belt?  In a way, this is manufacturing a homemade belt.  Right?  Basically, start with a backing material and apply an abrasive to it.  Does that make sense?  So, comparing our homemade belt to commercially manufactured belts:
 

1. Strength and stability of the backing material.  Good.
   
2. Consistency of the abrasive particle size.  Good.
   
3. Well bonded abrasive particles.  ???
   
4. Consistent abrasive particle distribution on the surface. ???
   

 
Leather is soft and porous.  Some of the abrasive particles will become loosely embedded in the surface of the leather, but not actually bonded to the surface.  If the particles are embedded enough to sort of hold them in place, they are only partially exposed because, by definition, they are embedded.  This creates an uneven surface.  The rest of the particles will be “bonded” to the surface to the extent of the strength of the emulsion adhesive properties after the emulsion has dried. Is this as strong as the bonding of regular belts?
 
With our homemade belt, can we match the consistency of abrasive particle distribution with that of commercially manufactured belts?  My very best, fairly educated without actually testing it guess is, no.  Probably not even close.
 
Conclusions:
 
Pros:
 
Compounds may be available in particle size not available in a bonded abrasive.
Possibly less expensive in the long run.
Quick and easy to refresh a belt.  Kind of like belt in a tube!
 
Cons:
 
Not as effective as a bonded abrasive.
Less evenly distributed particle distribution.
Abrasive bonding not as strong.
Probably not water, oil or solvent resistant adhesion.
 
Everyone starting out in sharpening runs across compounds and emulsions and it’s easy to be enticed into thinking they are in some way necessary, or may even be that special sauce needed to get that elusive perfect edge. 
 
As far as I can tell they are just another form of abrasive and useful in some circumstances.  Not some special sauce, but just another tool in the box.  Nothing more, nothing less.

What do you guys think?

[Rupert Lucius]

Rupert, agrees with grepper -

"Everyone starting out in sharpening runs across compounds and emulsions and it’s easy to be enticed into thinking they are in some way necessary, or may even be that special sauce needed to get that elusive perfect edge".

"As far as I can tell they are just another form of abrasive and useful in some circumstances. Not some special sauce, but just another tool in the box. Nothing more, nothing less".

Knowing how to "read the edge" and having a "moving abrasive" (at hand) are to me what helps one to become a good sharpener..

[Mark Reich]

That’s very interesting Mark.
 
I’ve look around for CBN belts and have not been able to find any.  I wonder why?
 
So what linen belt do you use for the 80u CBN compound?  What weight?  Can you point me to one?
 
Can you really get an even grit distribution applying compound, better than say 220 grit bonded abrasive ceramic belt?
 
I would think that because the abrasive is not really fixed to the surface when using compound, that it would be less effective than a bonded abrasive belt.  It sounds like you are finding differently.

Are you really saying that just smearing on emulsion like this  works better than a bonded abrasive belt?
https://www.youtube.com/watch?v=IxJMSHR907s

I'm always willing to try/learn something new.

LOL!!  Wow! A blast from the past. I took that video of Ken in my old shop a few years ago.

To be fair, we shot that in one take. I don't think Ken had ever applied compound to an upright 1x42 before. I wish he would have been running the camera. I was very familiar with that operation by then, but Emulsions were new, as I remember. I use them on leather.

So yeah, that's about all there is to it, except I don't use a rubber glove to apply grit. It still makes me laugh when I think about that conversation. Rubber gloves... lol   Ken has a surgical background. I'm just a hick from the sticks.

The reason you don't see CBN belts is probably because the abrasive is really expensive, and almost nobody knows how to keep CBN or diamonds on a belt. Everyone is satisfied with the same old cheap stuff that's been available for a hundred years. I know someone makes a diamond belt, but they are truly outrageously priced. Like one 2x72 belt costs as much as a bottle of compound. 

You're right, it's counterintuitive to think that "loose" grit stays on a belt better than bonded grit, but it does, and I'll try to explain how I think this happens. 

The compounds I use on linen belts come with an oil base carrier. This "wet" carrier sticks to the belt, and the "loose" grit stays with the carrier. The grit can move on the belt without coming off. The cohesive property of the fluid carrier allows the grit to "tumble" on the belt without coming off, and I think I can prove it. 

When I have a freshly loaded belt, there is some excess compound on the belt. When I make a pass on a blade, that excess compound stays in a neat little line of wet compound on the blade. I wipe it off the blade with my dirty finger and put it right back on the belt, and I keep doing that until I get tired of it or until I accidently wipe it on my pants.

Bonded grit has no such flexibility or cohesion. It can't move in any way except to break off and become airborne. We all know how quickly and easily that happens, especially with a new belt. When the blade touches the belt, much of the brittle grit comes off immediately in a cloud of particles, and they don't come back to land on the belt. 

When I make my first pass on a regular belt, not only can I see and feel the grit exiting at high speed, there's dust on the blade. I've tried to put the dust back on the belt, but it's never helped much.

That's my story. It changes when I talk about water base compounds on leather belts, but you wouldn't believe me if I told you how well that works anyway.

Now, I haven't seen any other kind of linen belt, but I haven't been looking. After Mr.Rupert sent me some of these linen belts years ago, I bought in bulk. Sorry I wasn't clear about the linen belts.

Mr. pjwoolw is extremely knowledgeable. His word is gold, and I'm very happy to see him here. I've said this before, and I'll keep saying it- I feel very humbled and honored to be here, on this forum, with this League of Extraordinary Gentlemen. Not just sharpeners- Gentlemen.

Surprisingly, many of us here today have known each other for a long time. We sorta "grew up" together on a different forum that was very special indeed.  

We're still carrying on, going about business as usual. Not much has changed, yet the world seems a little brighter once again.

[Rupert Lucius]

Thanks Mark - please reflect on the miles that you have traveled - what a trip.

One's journey and life are so short - do not waste a minute.

We are so fortunate to have you and your knowledge -


Rupert

[grepper]

Mark, I think it’s an honor to have you and all the other gentlemen here on this forum, and wish to express my thanks to you personally and everybody else for taking the time to share your knowledge.  It’s really appreciated!
 
Your depth of experience in everything knives, including sharpening, far exceeds mine.  When you share what you know, I know it’s from a lot of experience and not just spouting off like so much of the blather I read on the ‘Net.  Very refreshing. 
 
What was surprising to me was that you previously posted that an 80u CBN emulsion on a linen belt performed better than and lasted longer than a comparable regular belt.  Additionally, Mr. pjwoolw stated that he had been using the same linen belt with an 80u abrasive for 2 years!  I still don’t understand how an abrasive that can roll around on a belt could possibly perform as well as if it were solidly bonded.  I can certainly understand why it would last longer, I mean, it’s just rolling around on the surface.  But, I’m more than happy to accept that in practice it ends up that is just an academic curiosity.
 
How does the 80u CBN emulsion on linen compare in performance and longevity to a ceramic of about the same grit?  Is it actually a better performing direct replacement?   Can I just bail on regular belts?  Do you find the grit level is more consistent over the life of an application, rather than slowly getting smoother and smoother like a SiC belt does?  I hate that!  I love the idea of a CBN belt, and I’m more than willing to give it a try if the only way is the emulsion/paste on linen thing.
 
What an interesting subject!