Thread: Question on stones

I've been learning about coticules and other stones I guess they're called...

I've never used one. Only just got my first swaty 2 days ago (thanks member here!). I say that to say I've only seen these things ib pictures.

The coticules are average $200+

Why can't you use a slab or granite? Marble? Hell, a smooth brick (okay that is obvious).

Originally Posted by rickboone

I've been learning about coticules and other stones I guess they're called...

I've never used one. Only just got my first swaty 2 days ago (thanks member here!). I say that to say I've only seen these things ib pictures.

The coticules are average $200+

Why can't you use a slab or granite? Marble? Hell, a smooth brick (okay that is obvious).

A mint vintage coticule went for just north of $100 on ebay a couple of days ago. You don't need an 8x3 natural combo to hone a razor. A bout (irregular shape) will do it and much more cheaply. You don't need a 'select' either. The regular will do the job though it may not be as cosmetically appealing. Shoot a PM to zib and see if he has any stock left.

A slab of granite or marble has undoubtedly been tried. When you read of the obscure rocks that have been dug out of the ground and lake beds and used for honing all over the world it is a true testimony of the ingenuity of man. IOW, if a brick would work we would be posting about the great job my Home Depot brick did on my dubl duck.

Yes, but what is the difference in the stones? In other words why can't a piece of granite work? What is the differences in the make up of the stones that makes them suitable? Hardness? Smoothness? Pourousness or lack thereof?

Originally Posted by rickboone

Yes, but what is the difference in the stones? In other words why can't a piece of granite work? What is the differences in the make up of the stones that makes them suitable? Hardness? Smoothness? Pourousness or lack thereof?

Other stones would work, but aren't likely to work as well as the ones normally used. Like you suggest, the hardness of the material, the fineness of the particles, the shape and consistency of the particles, etc. all can make a difference.

And yes, one can indeed sharpen a knife on a brick or cement block. But I wouldn't want to shave with a razor sharpened that way.

Hones that cut metal efficiently have an abrasive embedded in a binder. Coticules have garnets and Thuringan types such as Eschers have quartz. A piece of granite or a brick doesn't have the abrasive and the binder that would make it appropriate for honing a razor or a knife. Not efficiently anyhow.

i would suspect its something with how they break down

Originally Posted by rickboone

Yes, but what is the difference in the stones? In other words why can't a piece of granite work? What is the differences in the make up of the stones that makes them suitable? Hardness? Smoothness? Pourousness or lack thereof?

There are a lot of differences, and at the end of the day the combination of all is what makes some stones better than others at scratching the metal in quick enough and in uniform fashion.
You have more than one piece of sharp metal laying around, what makes some good to shave and not others? No different with stones.

Originally Posted by rickboone

Yes, but what is the difference in the stones? In other words why can't a piece of granite work? What is the differences in the make up of the stones that makes them suitable? Hardness? Smoothness? Pourousness or lack thereof?

All of the above: hardness, smoothness, porosity, uniformity and more.

The first important part is the size of the harder steel cutting, scratching grains. You want them to be uniform and of the correct size for the stage in the polishing. The matrix that holds the cutting bits need to be soft enough to expose them but strong enough to hold and manage them.

Many hones are meta-sedimentary rocks. The metamorphic process commonly begins with a clay, silt or mud stone that is a mixture of clay and very fine quartz grains. Mother earth bakes the rock enough to keep it together but not so much that it recrystallizes into larger crystals and gets harder than a brick. I have heard of hone being made or improved by low firing soft natural stone.

Some like the Belgian water hones are unique in that they have grown microscopic garnet crystals. Garnet being harder than quartz but not insanely hard makes an ideal abrasive for steel. It also grows in a shape that
helps with the honing process. I wish I knew what the magic in the Japanese naturals was.

Granite as a crystalline rock can be found in very fine uniform grain sizes
but the matrix so strongly binds it all together that it does not make a good hone. Such very fine rock might be used with a light sprinkle of loose abrasive
and water. Why bother there are already good hone rocks so we do not need to pound a square peg into a round hole.

Of interest if the grain size is fine enough to be a hone the grains are too fine to discover what type of rock it is without a microscope and chemical work. Geologists have grab bag generic names for these fine grain rocks like aplite and trap.

BTW: As a geologist I can tell you that true granite is uncommon. What the kitchen counter store calls granite is almost always not. Granite is chemically uncommon as far as rocks go.

Originally Posted by rickboone

Why can't you use a slab or granite? Marble? Hell, a smooth brick (okay that is obvious).

Actually you can. Well, at least with the marble; there are two deposites of marble honestones in the US. Unfortunately, the reference I have names only one, and that is in Hardin County, Kentucky. There is also a reference to marble being suitable to use as a razor-hone in volume 62 of The American Mercury.

As far as granite is concerned, I know one collector who has a small block which he told me puts a "razor-sharp" edge on his knives, although people who don't use a straight often have a different understanding of the term razor-sharp. There are a couple of granite deposits that have been used to make grindstones, but nothing fine enough to be of interest to us.

Kindest regards,
Alex

[QUOTE=niftyshaving;521664] I wish I knew what the magic in the Japanese naturals was.


QUOTE]

Fom looking at pictures, could it be perfect chaos in terms of particle shape? In contrast the garnets show if not perfect symetry, a high degree. The chaos of the Japanese stone allows for tight packing of the particles thereby not allowing them to cut so deeply into the metal.