A stone , water and steel.

[ovidiucotiga]

Hey guys.

I need your help...i'm stuck.

In my free time i endulge in my hobby of restoring old japanese razors and cooking knives...it's a fun and rewarding way to give life back to quality instruments that can be used once again.

I use japanese natural stones to polish them. I use them with tap water and a rubbing stone from the same piece of stone.

A slurry(paste formed with water ) is raised on the surface of the stone with the rubbing stone. The razor or knife is honed in that paste on the surface of the stone.

It is known that these stones bring out the steel pattern in hand forged carbon steel blades.

I have researched a lot about steel and metalurgy and i understand that soft steel has a diffrent christaline structure - austenite then hardened steel - martensite...these structures respond diffrent to abrasive ware and corosion due to their BCC and FCC configuration.

I also noticed that when the carbon steel sits to much time in this slurry rust starts to form...sure carbon steel rusts in the water i am using if left a long time but in the slurry the process is accelerated...like in a few minutes ... compared to say half an hour in water.

The slurry also if used as a polishing paste on a shiny clean piece of carbon steel it tends to dull the finish a bit and add a thin gray layer on top of it....like a passivation layer.

So i suspect something in the stone is reacting with water at room temperature to facilitate a redox reaction with the steel.

These stones have been studyed intensly in Japan because they are unique and some of the finest natural honing/polishing stones nature gifted mankind....But they have been studyed from a geological point of wiev...and a practical point...i did not manage to find any info about the chemestry involved.

I did managed to find a SEM composition chart of a few similar samples to the ones i am using.

I also ordered a pH meter to test the pH level of the water i am using and the slurry solution.

 

 

So bottom line...can any of you guys look at the components in the table and see if any of them can react with water at room temperature  and the Fe in the steel to promote any kind of redox reaction or rust formation? i know that some of the components like those representing the abrasive particles in the stone are stable but i belive that the clay binder may have components capable to react in these conditions with the steel....it just surpasses my level of knowledge snd i need some help understanding or guydance on where to continue my research.

Your help would be greatly apreciated.

I also added an example of work these stones are capable of so you can better understand what i am asking.

http://www.nihontoantiques.com/archive/polishing, step by step.htm

You can click on the images to enlarge them.

Thank you guys, have a nice day!

 

 

 

 

 

[StringJunky]

How do the Japanese swordsmiths avoid the problem when they polish a newly made sword?

[ovidiucotiga]

Well I presume the stone/slurry form some kind of protective oxide? layer on the surface of the steel preventing further rust formation.

The rust formation I noticed was actualy a test I condu on a clean piece of steel...I put one drop of slurry and one drop of water on a shiny degreased piece of carbon steel and let them sit for @ half an hour...then whiped the steel dry. I noticed both drops left behind a gray area...and signs of red rust on the margins on the border with the clean steel.

 

But the gray spot was more pronounced where the slurry was...also took more to polish out so I presume it was a bit deeper.

 

 

 

[StringJunky]

46 minutes ago, ovidiucotiga said:

Well I presume the stone/slurry form some kind of protective oxide? layer on the surface of the steel preventing further rust formation.

The rust formation I noticed was actualy a test I condu on a clean piece of steel...I put one drop of slurry and one drop of water on a shiny degreased piece of carbon steel and let them sit for @ half an hour...then whiped the steel dry. I noticed both drops left behind a gray area...and signs of red rust on the margins on the border with the clean steel.

 

But the gray spot was more pronounced where the slurry was...also took more to polish out so I presume it was a bit deeper. i wondered if the rust in the slurry was metal particles that have gone rusty and the actual surface of the metal was not corroded. that greying sounds like a patina of some sort.

 

 

 

Looking into it:  magnetite is the red, rusty stuff and that is produced with a plentiful supply of air and moisture (and electrolytes). Haematite, or hematite, is the grey patina, which is produced in the areas where air and oxygen  is more limited. That concurs with your observation that the red rust is on the perimeter of the puddle you made, where the air will be at highest concentration with the water. The middle submerged section is grey because that surface is relatively cut off from the air. Rust and corrosion needs air, moisture and electrolytes to form rust. If you could limit the air somehow whilst working with it wet that would help. Using boiled water would get the air out but working with the slurry will put it back in.

 

I'm sure someone with deeper chemical knowledge will elaborate at some point.

Edited March 7, 2018 by StringJunky

[ovidiucotiga]

I seems they use the slurruy with oil at some point probably to stop the reaction but what puzels me is if something in the stone reacts with the steel in any way...and what would the reaction be.

[StringJunky]

1 hour ago, ovidiucotiga said:

I seems they use the slurruy with oil at some point probably to stop the reaction but what puzels me is if something in the stone reacts with the steel in any way...and what would the reaction be.

My guess is the oil cuts off the oxygen whilst the metal is being abraded.

[Area54]

The table is not directly helpful. For example, magnesium will not be present as magnesium oxide, but as a component in a ferromagnesian mineral such as an amphibole. Presentation of the composition as oxides is as convenient and conventional approach.

[StringJunky]

30 minutes ago, Area54 said:

The table is not directly helpful. For example, magnesium will not be present as magnesium oxide, but as a component in a ferromagnesian mineral such as an amphibole. Presentation of the composition as oxides is as convenient and conventional approach.

Would the components of the slurry be stable and in equilibrium anyway?

[Area54]

15 minutes ago, StringJunky said:

Would the components of the slurry be stable and in equilibrium anyway?

I'm not sure. It would help to know what the rock type is. My initial thinking was that this was probably a volcanic ash. My recollection is that these can make good whetsotnes. The high silica content would be consistent with an acidic magma which, in turn, is consitent with explosive eruptions and hence the ash. However, the alkali % is low and alumina % is high, so we are likely dealing with a clay matrix, weathered from the original feldspars. All this is off the top of my head speculation. If it is clay then these can be very reactive.

[StringJunky]

4 minutes ago, Area54 said:

I'm not sure. It would help to know what the rock type is. My initial thinking was that this was probably a volcanic ash. My recollection is that these can make good whetsotnes. The high silica content would be consistent with an acidic magma which, in turn, is consitent with explosive eruptions and hence the ash. However, the alkali % is low and alumina % is high, so we are likely dealing with a clay matrix, weathered from the original feldspars. All this is off the top of my head speculation. If it is clay then these can be very reactive.

I think he's using water stones but he would have to tell us if his are composite or natural. They can cost serious money. These are some:

https://www.knivesandtools.co.uk/en/ct/japanese-sharpening-stones.htm

[Area54]

My impression was that they were natural, else he would not have referred to a "geological analysis". I did google for more info, but in the half dozen links I looked at none of them specified the formal rock type.

[dimreepr]

From what I remember, the clay slurry is layered as insulation, meaning the expertise is in a heat treatment. The swords effectiveness is that its hardest at the cutting edge and softest (more pliable) at the blunt edge; a lot like combining steel and concrete.

Edited March 7, 2018 by dimreepr

[ovidiucotiga]

ok so to clear things up.

Japanese naturl whetstone or JNATS for short are natural stones.

From my research they formed @ 250 milion years ago. Thery are a layered stone formed on the bottom of the ocean from the tests of radiolarites:

http://www.sciencephoto.com/subject/Animals/protozoa/radiolaria

and clay

 

"

Clays carried by the wind and the remains of microbion called Radiolaria (Phosphoric Acid Calcium CaHPO4) which inhabited the deep sea, accumulated silently and slowly at a rate of approximately 1mm per 1000 years. This accumulation occurred thousands of kilometers away from Japan around present day Hawaii , and resulted in various strata, all with differing characteristics.

Heavier substances such as oxidized iron (Fe2O3) precipitated first and formed the “kawa (the skin)” and the remains of Radiokaria and the clay settled on top of that consisting silica shale. When the ocean was calm the settlings formed stratum that can be used for sharpening stone, and when rough formed “gokudou” stratum which has too many impurities thus cannot be used for sharpening stones.

These are the stratum which were formed by a mix of the remains of Radiolaria and clay, the latter acting as a cutting substance and the former as binding or glue and at the same time absorbent matter of lubricant (water).

" source:

http://www.japan-tool.com/tech_knlg/toishi/Awasedo.html

So i guess the clays carried by the wind could contain volcanic ash....good observation.

 

 

The stones i use are high end japanese natural stones from the best mines they had....same  quality stones the sword polishers used...but all JNAts in the layer behave similar....they all have this effect on iron...they kind of etch it...i use natural sharpening stones from allover the world and this phenomenon is somehow unique to these Japanese Natural Whetstones....that's why i'm trying to find what makes them tick.

 

Dont get me wrong...their effect on steel is not a flaw it's what makes them unique and helps them give outstanding finishes on blades that you cant get any other way.

 

Also another article on them under the SEm microscope.
 

https://scienceofsharp.wordpress.com/2014/05/28/does-j-nat-slurry-break-down/

and part 2

https://scienceofsharp.wordpress.com/2016/03/29/jnat-slurry-part-2/

 

the way the steel is treated is of no interest atm to me although it is fascinating.

 

What hurts me the most is that idont understand if this type of finish is due to the abrasive particles alone or does something in the binder react with the steel to help.

 

 

 

[dimreepr]

16 minutes ago, ovidiucotiga said:

ok so to clear things up.

Japanese naturl whetstone or JNATS for short are natural stones.

From my research they formed @ 250 milion years ago. Thery are a layered stone formed on the bottom of the ocean from the tests of radiolarites:

http://www.sciencephoto.com/subject/Animals/protozoa/radiolaria

and clay

 

"

Clays carried by the wind and the remains of microbion called Radiolaria (Phosphoric Acid Calcium CaHPO4) which inhabited the deep sea, accumulated silently and slowly at a rate of approximately 1mm per 1000 years. This accumulation occurred thousands of kilometers away from Japan around present day Hawaii , and resulted in various strata, all with differing characteristics.

Heavier substances such as oxidized iron (Fe2O3) precipitated first and formed the “kawa (the skin)” and the remains of Radiokaria and the clay settled on top of that consisting silica shale. When the ocean was calm the settlings formed stratum that can be used for sharpening stone, and when rough formed “gokudou” stratum which has too many impurities thus cannot be used for sharpening stones.

These are the stratum which were formed by a mix of the remains of Radiolaria and clay, the latter acting as a cutting substance and the former as binding or glue and at the same time absorbent matter of lubricant (water).

" source:

http://www.japan-tool.com/tech_knlg/toishi/Awasedo.html

So i guess the clays carried by the wind could contain volcanic ash....good observation.

 

 

The stones i use are high end japanese natural stones from the best mines they had....same  quality stones the sword polishers used...but all JNAts in the layer behave similar....they all have this effect on iron...they kind of etch it...i use natural sharpening stones from allover the world and this phenomenon is somehow unique to these Japanese Natural Whetstones....that's why i'm trying to find what makes them tick.

 

Dont get me wrong...their effect on steel is not a flaw it's what makes them unique and helps them give outstanding finishes on blades that you cant get any other way.

 

Also another article on them under the SEm microscope.
 

https://scienceofsharp.wordpress.com/2014/05/28/does-j-nat-slurry-break-down/

and part 2

https://scienceofsharp.wordpress.com/2016/03/29/jnat-slurry-part-2/

 

the way the steel is treated is of no interest atm to me although it is fascinating.

 

What hurts me the most is that idont understand if this type of finish is due to the abrasive particles alone or does something in the binder react with the steel to help.

20

Do you want an explanation, or confirmation?

[ovidiucotiga]

A confirmation ...i did some tests to confirm my findings in the past ... i know the slurry changes the pH of the water used....i used pH paper...i know that the slurry darkenes the steel much faster then plain water...i also know that it accelerates oxidation at the slurry steel interface....

An explanation is what would make me happy...i know all this stuff has to happen somehow...i also belive i managed to find some pieces of the puzzle but i dont think i'm there yet to put them all togeter....i will keep searching...perhaps i will find more info in geological studeys or japanese studeys on these stones.

 

But until then any info or guidance would be apreciated.