Sharp tools with matte finishes

[Bob Strawn]

It is easily possible that the misty appearance is caused by chemistry, but my own suspicion would be that the chemistry that causes the mist is the lack of chemistry. Diamond grits always seem to make a haze for me. Fixed, in water or in oil. Diamond apart from its pizeo effects, I would expect to be as chemically neutral as you are likely to get.

My suspicion is that grits that wear down to flat scraping surfaces, rather than remaining pointy will make for a more reflective surface. Steel can be pushed around quite a bit on the micro scale, and the flat surfaces on grit, may be pushing/scraping and filling in scratches.

I have noticed that when using a hazy polish burrs are much easier to clean up. Burr removal is the last and most likely opportunity for a good edge to be ruined.

While I do not consider my mirror edges duller than my misty edges, I consider the process of getting a misty surface, more consistently makes a perfect edge. I probably have to tweak a 2.5" mirror edge a few extra times to get it consistently sharp along the entire edge as compared to a misty edge.

Bob

[Jon van der Linden]

Japanese blades, especially swords, are made up of steels of varying hardness. In a sword there is a wavy line along the length of the blade that is very important to the aesthetics of the blade. A true mirror polish would hide this. Similar variation can be seen in chisels and plane blades. This is why the softer matrices of the natural stones are more desirable.

There are stones with high grit numbers that won't give a mirror polish, but grit being equal, the mirror polish is a flatter. There were some mentions in this thread referring to Ron Hock's blog and the final result there was "The Shapton’s grit grains are better anchored in the stone surface which allows them to shear a straight groove in the steel, carbides and all, thus creating the flatter surface." The full blog post is here:

http://hocktools.wordpress.com/2010/...ystery-part-2/

[David Keller NC]

There are stones with high grit numbers that won't give a mirror polish, but grit being equal, the mirror polish is a flatter.

Jon - This point was addressed a while back. Mirror polish doesn't equal flat topology, on either the micro or macro scale. While it's true that a relatively scratch-free surface (or a uniform layer of very small scratches) is a necessary pre-condition for a mirror polish, that doesn't mean that a hazy, silvery-gray or matte surface is rougher than a mirrored surface. There is simply too much variation in the chemistry of steel alloys and stone binders/grits.

The only thing one might be able to infer is the obvious - that taking the same tool from one stone to a finer stone in a series of identical stone chemistries will produce a more uniform micro topography to the surface.

[Jon van der Linden]

Jon - This point was addressed a while back. Mirror polish doesn't equal flat topology, on either the micro or macro scale. While it's true that a relatively scratch-free surface (or a uniform layer of very small scratches) is a necessary pre-condition for a mirror polish, that doesn't mean that a hazy, silvery-gray or matte surface is rougher than a mirrored surface. There is simply too much variation in the chemistry of steel alloys and stone binders/grits.

The only thing one might be able to infer is the obvious - that taking the same tool from one stone to a finer stone in a series of identical stone chemistries will produce a more uniform micro topography to the surface.

While there may be chemical action, I suspect that it's primarily mechanical. Try laying the blade down on the stone, come back in an hour and see how far that goes towards changing the finish.

Unless I missed something, the metallurgist Ron Hock consulted explained the matte finish entirely by mechanical action.

I don't understand why you disagree with the results I quoted or why you think that my statement regarding equal grits is false. Perhaps you can explain it in a way I can understand.

[John Kali]

I'm no expert at sharpening tools, but the picture on the right was magnified 495x, the one on the left is magnified a bit less at 467x. I think this could play tricks on the mind, because had they magnified the picture on the left at 495x it may very well have looked exactly the same as the one on the right.

[Christian Castillo]

One can always look to the industry that has had access to both high quality natural and synthetic stones for the longest time and see what they use. I am talking about the Japanese carpentry and woodworking trades and from what I've read, they only use synthetic stones up to around 2000 grit. From there on, they use natural stones. Now this could be due to some type of tradition or reverence for the past, but time is money and these people are professionals, so I assume they are going for a sharper blade,a longer lasting edge, or what just plain gives the best result. Having dug around the net, here is a quote from So Yamashita (www.japan-tool.com),

"Using natural stones will enable you to plane thinner (more sheen on the surface of the wood) and at the same time it will make the edge last longer. This has a good reason. The sharpening particles of the synthetic stones are even in their sizes, whereas the natural one's are not. Therefore blade sharpened by synthetic stone will have even height of serrated teeth, so once those teeth gets dull it stops cutting altogether, but... when the height is different... I think you see my point. It's like the shark's teeth. They don't break all at once.

Also, the natural stone sharpening has a hardening effect on the tip of the blade. This has been proven scientifically by the HRC testing machine, experiment done by renowned plane blacksmith Usui Kengo. The hardness was actually harder after being polished by a fine Nakayama stone. So you see, it's not just about the sharpness you are getting from natural stones. Once you use natural stones, it will be unthinkable not to finish with them."

This observation has also been observed by Alex Gilmore (www.thejapanblade.com) and explained in his article, "Sharp vs Shiny":

http://www.thejapanblade.com/sharpvsshiny.htm

I must say that this is a very interesting subject, and I believe that either medium will give the user an edge sharp enough that the quality of his work will be dependent entirely on his/her skill. Natural or synthetic, when you are literally splitting hairs... anything after that is just splitting hairs.

[dan sherman]

I don't understand why you disagree with the results I quoted or why you think that my statement regarding equal grits is false. Perhaps you can explain it in a way I can understand.

I think what David disagrees with, and I do as well, is this statement.

but grit being equal, the mirror polish is a flatter

A high polish does not mean the surface is flat.

[Jon van der Linden]

)

"Using natural stones will enable you to plane thinner (more sheen on the surface of the wood) and at the same time it will make the edge last longer. This has a good reason. The sharpening particles of the synthetic stones are even in their sizes, whereas the natural one's are not. Therefore blade sharpened by synthetic stone will have even height of serrated teeth, so once those teeth gets dull it stops cutting altogether, but... when the height is different... I think you see my point. It's like the shark's teeth. They don't break all at once.

Also, the natural stone sharpening has a hardening effect on the tip of the blade. This has been proven scientifically by the HRC testing machine, experiment done by renowned plane blacksmith Usui Kengo. The hardness was actually harder after being polished by a fine Nakayama stone. So you see, it's not just about the sharpness you are getting from natural stones. Once you use natural stones, it will be unthinkable not to finish with them."

In Japan most blades use at least 2 or 3 types of steel. Showing the blacksmith's art can only be done with a matte finish, a true polish will hide these different steels and make them look uniform. With a Japanese sword there are even different degrees of polish for different parts.

As for the often cited HRC test, polishing steel (as in any sharpening process) will harden it. I've never seen the actual test report, but if there's no comparison to a range of stones, then it's already suspect. It's also extremely difficult to accurately test the edge of a blade, these machines are designed for testing flat surfaces. Hardness is also something that can be built into the blade to start with.

When it's said that natural stones leave a longer lasting edge, I'd be very curious to test that with Western blades, O1, A2, S53... I suspect that if you want long lasting edges there are many other solutions than a $1500-$2000 finishing stone + a small armada of others to get there....

[Christian Castillo]

I too would like to see testing done on western steels. Off topic, one can find natural stones priced reasonably compared to synthetic solutions. They just wont be as aesthetically pleasing, of equivalent size as a pricier stone or mined from a renowned location.

[Christian Castillo]

I can't help but feel that this thread is shifting towards a discussion on the optimum sharpening solution. This thread is about the effectiveness of a matte finished edge so I will just leave it at that. I do, however, feel that a discussion on natural vs synthetic stones would be worthy of it's own thread and highly interesting. Various steels could be tested and sharpened on synthetic and natural stones and then used in a hand plane. Wear could then be observed after so many passes. This would be a great experiment. Hopefully Brent Beach is reading this.

[David Gendron]

I think we have people that are just not in favor of japanese tools and techniques and they try to make there points.... and people that try to show other tools and techniques, than the western(British/American) one we all know and are used to, and it seem to offend some of the non Japanese tool users! I think here the only thing that the OP was doing, is sharing some valuable informations on other tools/techniques/results of a different culture!
In my case, when a thread dosn't interest me, I don't chime in! When it does, I do and I try to do it in respect of the OP and others who have posted!

[Christian Castillo]

One cannot even say that this is about japanese tools and techniques as sharpening mediums most likely exist all over the world that can create matte finishes ( Arkansas Stones, Belgian Coticules, silicon carbide on lapping plates). However, what you have described David has happened. Had the OP began this conversation with a hazy finish created by a European natural sharpening stone, would this have happened? I view the information presented here as universal. This is about steel and sharpening, and thus is valuable to all woodworkers.

[David Keller NC]

I think what David disagrees with, and I do as well, is this statement.


A high polish does not mean the surface is flat.

Indeed, though I'd put a subtler nuance on it. The reflectivity of a surface is influenced by a great deal more than topology - so much so that no valid conclusions can be drawn about the surface roughness, even among similar, but slightly different, materials - such as different alloy steels, and even the same alloy but from different batches.

There are, however, several measures of surface roughness that are routinely measured with relatively simple equipment that would make an interesting study, though this equipment is probably beyond the typical woodworker's (and mine's!) budget.

Regarding the differences between natural japanese waterstones and synthetic stones and their effect on different steels, Toshio Odate has a fair number of electron micrographs of these combinations, and a good discussion/interpretation of the results in his book "Japanese Woodworking Tools".

[Dave Anderson NH]

As a point of reference and related to Dave Keller's remark. Industrially, surface finishes are measured in micro inches. A scale exists and sample kits are available with samples from 256 down to 2 micro inches. The low numbers are the finer ones. Without a kit available now I'm going to give the example of the Marples Blue Chip chisels. The surface finish from the factory is about halfways between 16 and 32 microinches. Normally the incoming inspection department at a company will do a visual inspection of incoming machined parts using the sample kit and accept or reject on that basis. For critical applications, the sample of the part and the reference sample will be placed side by side on a binocular microscope. The symbol used on mechanical drawings is the finish number placed beneath a square root symbol.

[Mark Roderick]

After all this, now I feel bad that the edges on my planes and chisels are always shiny after sharpening!