Sharp tools with matte finishes

[Jon Toebbe]

I think we are all in violent agreement on this issue, just stating it differently.

Very well put! Ron Hock's blog post that was referred at the start of this thread was an interesting read. For what it's worth, I strop with chromium oxide and get nice, shiny bevels. I've been well pleased with the results when steel meets wood. Less so when steel meets embedded nail... but that's a different thread entirely!

[David Weaver]

I don't post here often, and couldn't remember if I was banned.

but if one wants to wonder about the real size of the scratches left by stones w.r.t. the observable service (shiny or not), there is no need to look past the work alex gilmore has done.

http://www.thejapanblade.com/test521.htm

I'll guarantee if you look at a shapton 30K edge reflecting light, you'll squint.

I'll also guarantee that if you look at the edge left by one of these suita stones, you won't squint.

I don't fully understand the difference (why one shines and why one doesn't, why natural stones cut hard steel fast but leave no nasty grooves in the backing iron but synthetics do cut both fast), and i don't care. I also won't say that it's necessary for anyone to buy natural stones. But they (the good ones) do feel nicer than artificial stones for freehand sharpening, they smell nice and they do a good job - as good as synthetics at least. What's wrong with enjoying yourself when you're involved in a hobby?

One would have to count strokes taken from an edge before it stops cutting to find out what is really better. Any volunteers? The number of strokes to do the comparison could be several hundred to a thousand strokes per sharpening, and you'd have to do that multiple times to get remotely credible data.

Not liking a certain type of tools and not having used them is no reason to assault someone who does and try to decide what curiosity they can satisfy based on what professionals "laugh at".

[Mark Roderick]

"If your sharpening method leaves you with scratches that range from 0.5 to 1 micron deep that are more random in arrangement, that will leave you with an equally sharp edge that has a matte finish."

I don't think the "random arrangement" concept is correct. I can sharpen a tool using any motion, from circular to back and forth to sideways to all of the above, and the sharpened edge always ends up shiny.

Same thing with rubbing out a finish. You use the rougher pad to take the finish to a matt, then the finer pad to bring it to a higher gloss. It doesn't matter in what direction you rub the fine pad - it still comes out to a gloss. In fact, you can use a random-orbit machine to rub out the finish!

But there must be something to the point about the depth of the grooves. You're saying that what distinguishes a shine from a matt is that the grooves on the shiny surface are all the same size? Maybe that's true. If it is true then it's the answer to this age-old debate.

[Wilbur Pan]

But there must be something to the point about the depth of the grooves. You're saying that what distinguishes a shine from a matte is that the grooves on the shiny surface are all the same size? Maybe that's true. If it is true then it's the answer to this age-old debate.

That actually is true. If you have a distribution of different sized grooves, that will diffuse light more than a collection of same sized grooves, which will be more reflective.

As far as the random orientation of the grooves goes, all I can say is that (1) a random orientation of grooves will diffuse light more than grooves in a repetitive pattern, and (b) look at Ron Hock's electron micrographs. There clearly is a more random orientation in the scratches left by the natural Japanese waterstone.

I think what is happening is that both the wider distribution of groove sizes and the random orientation are contributing to the matte appearance. It's not an either/or thing.

[Christian Castillo]

Wilbur has brought up a great point. I have used tools sharpened by both synthetic and natural stones, both get wickedly sharp, "shinyness" isnt the sole requirement for sharp. In fact, the sharpest blade I've ever had the pleasure of using was of matte finish and came off a suita stone. As for a previous comment regarding japanese tools and softwoods, I recall that Derek Cohen, member on this board and various others, uses japanese blue steel chisels and he primarily works australian timbers. That should say something regarding the ability of the chisels to hold up in hard wood.

[Jim Koepke]

While contemplating the posts in this thread I happened to glance over to my note board. I noticed one of the notes there held up by a push pin. Admittedly the push pin does have a large head, but there were no less than 27 angles dancing gleefully upon it.

I do not wish to imply that this is the maximum that can fit upon the head of this pin, nor do I wish to further such an argument.

I choose not to split hairs over methods of achieving sharpness. I choose to seek methods of achieving sharpness that will split hairs.

I think it is time to head out to the shop.

jim

[george wilson]

You wax philosophical,Jim,while I get too grumpy!! It depends upon how much pain I am in,and what I'm taking for it.

I need to not get so grumpy. Whatever works for a person is o.k..

[David Keller NC]

Wilbur - One thing to remember in this discussion is that while a steel surface with a scratch pattern can have a matte (or more matte, as the case may be) appearance than a steel surface with fewer or less deep scratches on it, it's not correct to think that a scratch pattern is the only reason for a matte appearance.

In fact, there are two different processes at work - one is the surface imperfection pattern, which will scatter light and result in a less-shiny surface. However, one can also have a utterly smooth, nearly perfect steel surface that would otherwise be a mirror that still looks matte. This effect has to do with chemical changes on the steel surface, not scratch patterns. And the use of various combinations of differently-alloyed steels and different composition waterstones can cause such a chemical change.

In other words, degree of reflectivity doesn't equal topology of surface.

[Wilbur Pan]

Can you elaborate more on the chemical changes? I am having a hard time picturing what could happen with a natural Japanese waterstone, steel/iron, and water that would result in a chemical change.

The two things that I can imagine would be some sort of oxidation or a very mild acid etching. But if either one of these was happening, there should be visible signs of that in the electron micrographs that Ron Hock posted.

[David Keller NC]

What's specifically happening is sensitively dependent on the exact metallurgy of the steel and the exact composition of the binders in stone. Many of these binders in both natural and man-made stones are alkaline in nature and can promote the hydrolysis of the iron surface to ferric hydroxide. If the binders are acidic, then it's possible to remove sufficient iron from the surface to leave behind mostly carbon and (depending on the alloy) chromium.

It takes very little of this surface change to make large changes in the reflectivity of a steel surface. While we don't typically work with stainless steels, an example of this sort of action that makes no measurable change in the bulk alloy composition but makes huge changes in reflectivity is passivation. In this process, either a mineral acid or citric acid and oxygen from the air removes the top few iron atoms from the steel surface and leaves behind primarily carbon and chromium. The surface has a "pickled" appearance, and is a matte silver-gray color where the original surface was a bright mirror remianing from electropolishing.

[Wilbur Pan]

Hi David,

I can see how those chemical reactions might be possible, but from a practical standpoint, does that really happen in the course of sharpening? As far as ferric hydroxide goes, the usual reactions to generate it that I have been able to find either involve a fairly alkaline environment, boiling temperatures, or an electrochemical reaction in a salt solution. I also am not sure that an appropriately acidic environment necessary to cause etching would exist during sharpening. Furthermore, If these types of reactions were occurring, there should be some evidence of it in the electron micrographs that Ron Hock has provided.

[Pam Niedermayer]

The temperature requirement would be satisfied by friction. Add to that a little vacuum of stiction by flat stones, maybe would add to retention of heat. Don't know about the alkaline content, but my guess is that, IRC from geology class 45 years ago, that stone is basic, or a lot of stones are.

Pam

[Brian Ashton]

By the way, I can put a polished surface on this chisel and plane blade with a manmade waterstone, and get a similar shaving. That should show that the polished vs. matte finish really doesn't come into play in determining how sharp a tool edge is.

I have shown people that you can get a usably sharp edge straight from the grinder if you're careful enough and have a set up like I do - very slow speed and fine grit, turners do it every day... Usuably is the key word as there are as many ideas about how sharp a tool is as there are stars in the sky. Basically if the tool cuts to your satisfaction and leaves the desired result it's sharp enough. Have a look at what the Egyptians 2500 years ago were making with tools most of us wouldn't even have in our little hobby shops sometime if you don't believe me. You can bet they weren't too concerned with grades of mirror finish on their tools.

But what you should really be talking about with respect to how "shiny" or "reflective" an edge should be is the relative time it will stay sharp. What you may not have noticed in those micro graphs is the more irregular edge produced on the "less shiny" edge. Those irregularities will break off much quicker and leave you with a tool that no longer has a usably sharp edge. The more irregular the quicker the edge will erode. The same principle applies to using a steel in the kitchen. It literally rips the steel of your knife and leaves it with a very ragged edge, relatively speaking. But it's an edge that will cut through most things in the kitchen extremely well. Because nothing, except bones, are all that hard in the kitchen the edge produced is quite adequate, or as I like to say usably sharp. And will stay that way for an acceptably long enough time. Long enough that there is no reason to go to such lengths as we do to obtain a mirror finish on the edge. In fact that micro serrated edge is a benefit in the kitchen.

Now I have to get back to learning regression analysis...

[Christian Castillo]

Hmmm this article states the opposite of what you are saying Brian and that an edge created by a natural sharpening stone in fact stays sharper longer. It also talks about the matte finish left by japanese natural stones as opposed to the shiny finish left by man made synthetic stones. It is written by Alex Gilmore, who is an extremely knowledgeable vendor and user of japanese natural stones. He analyzes the edges produced using natural and man made sharpening mediums. If you browse through the site, you can find pictures of scratch patterns created by natural stones estimated at 40000+ grit and compares that to a shapton 30000 grit stone. It's an interesting read, anyone care to comment?

http://thejapanblade.com/sharpvsshiny.htm

[David Keller NC]

Hi David,

I can see how those chemical reactions might be possible, but from a practical standpoint, does that really happen in the course of sharpening? As far as ferric hydroxide goes, the usual reactions to generate it that I have been able to find either involve a fairly alkaline environment, boiling temperatures, or an electrochemical reaction in a salt solution. I also am not sure that an appropriately acidic environment necessary to cause etching would exist during sharpening. Furthermore, If these types of reactions were occurring, there should be some evidence of it in the electron micrographs that Ron Hock has provided.

As Pam noted, a lot of the water stone binders are alkaline in nature, but it's hard to be specific with this - there's a lot of variation in the alloy elements in different steels, and variation in the chemical composition of abrasive stones. And the chemical reactions can be very complex.

But I do have personal experience with this in relation to the nodular iron material that L-N makes their planes out of. I flattened the sole of a 60-1/2 block plane on both a coarse diamond plate and 800 grit silicon oxide wet-dry paper. The surface left after the diamond plate is silver colored and shiny, though scratches were visible to the naked eye. After the SiC paper, the surface was rendered very, very smooth (no visible scratches), but an overall matte gray color. I've reproduced this effect on older chisels and plane blades (generally "cast steel") - some of them come off of the Norton and King 8000 grit waterstones a dull matte gray color, though you can still see yourself in the reflection. However, these same tools produced a shiny-bright surface from a Shapton fine grit stone (I think it was a 6000 grit, but not positive).