# How are synthetic water stones made?



## bennypapa (Mar 15, 2015)

I've read that they are made from aluminum oxide grit but how is that grit held together?

Is there an episode of how it's made for this?


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## panda (Mar 15, 2015)

with egg and flour


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## larrybard (Mar 15, 2015)

Sintering?


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## bennypapa (Mar 15, 2015)

panda said:


> with egg and flour



How does that not rot?


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## larrybard (Mar 15, 2015)

bennypapa said:


> How does that not rot?



Nah. He didn't say there was any yeast. So it's just like egg matzoh. Will last forever. Even if you plan to carry your stones through a desert for, say, 40 years.


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## Benuser (Mar 15, 2015)

No egg.


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## daveb (Mar 15, 2015)

Bake on convection?


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## Von blewitt (Mar 15, 2015)

Are we talking about stones or scones?


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## JBroida (Mar 15, 2015)

bennypapa said:


> I've read that they are made from aluminum oxide grit but how is that grit held together?
> 
> Is there an episode of how it's made for this?



I'm at a place where I can't type easily now, but if you don't see a response from me tomorrow, send me a reminder and I'll write something up.


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## Zwiefel (Mar 15, 2015)

Von blewitt said:


> Are we talking about stones or scones?



Huw wins!

Looking forward to Jon's response tomorrow.


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## panda (Mar 16, 2015)

easy bake oven


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## ptolemy (Mar 16, 2015)

you guys are terrible. LOL


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## Lizzardborn (Mar 16, 2015)

My guess will be some form of crushed corundum mixed with clay putty and baked.


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## no_one_just_Roy (Mar 16, 2015)

Yup, there are many ways. 
Some are fried, some are baked, some are meant to be eaten raw


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## daveb (Mar 16, 2015)

Lizzardborn said:


> My guess will be some form of crushed coriander mixed with clay putty and baked.



Better?


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## Asteger (Mar 16, 2015)

Synthetics? Manufactured from toxic sludge and coloured with artificial dyes. Never eat them, even the tasty-looking ones. Stick with naturals.


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## panda (Mar 16, 2015)

don't lick them, they're toxic cause full of chemicals, not natural.


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## JBroida (Mar 16, 2015)

Here we go.... i'm probably gonna repost this in my blog too (this is from something i typed up a few years ago)...

History of Synthetic Sharpening Stones

People have been passing down the knowledge of how to sharpen and polish blades with various tools for generations. To many, sharpening is a very familiar task. However, since the beginning of civilization, there has been a strong demand for sharpening tools and skills. Over time, these demands could not be met by just natural stones (including tennen toishi), and thus began the development of synthetic sharpening stones. 

North America was at the forefront of inventing synthetic abrasives. In 1895, an American company, called Carborundum invented carborundum abrasives as the first synthetic abrasive material. Following that, Norton, another US company, invented their own synthetic abrasives in 1901. Since then, industrialized countries have continued to develop abrasive materials. Over the years, these abrasives have became necessary for producing steels, ships, airplanes, cars, and many other things. 

The history of synthetic stones in Japan began towards the end of Taisho (the Taisho period was from August 31, 1879  December 25, 1926) to the begging of Showa (the Showa period was from December 25, 1926  January 7, 1989) in Kyoto. In the initial years, Kyotos synthetic toishi makers borrowed wood kilns being used for kiyomizu-yaki pottery. Later on, they started using threshing machines. During World War II, Hiroshima was a major center of production for synthetic toishi, and thanks to their great success at producing these stones, the popularity of synthetic toishi in japan began to rise.


Three Main Components of Synthetic Stones

Grain: the abrasive materials in the stone
Bond: the bonding materials in the stone that hold the abrasive particles
Pores: Bubble-like gaps between grain and bond that hold water and allow waste material to be washed away


Making Process of a Synthetic Stone



1. Mix raw abrasive materials together

2. Mix abrasive materials with bonding materials and stir together

3. Press the mixture into shape

4. Dry

5. Bake

6. Re-shape

7. Quality check

8. Wrapping

9. Shipping/delivery

Main Types of Toishi Production Methods

Vitrified method: Feldspar and other minerals are added to the main grain, and water is added to moisten the material. This is then pressed, dried and baked in a high heat kiln  1200-1350 degrees Celsius. This method creates stones that have great durability (and can be stored in water). If kept well, this type of stone should last very long time. Among synthetic stones, this is the oldest production process and is still in a common use.

Resinoid method: Phenol, benzenol, and other plastic are added to main grain as bonding material. This material goes through the same process as vitrified stones. However, the baking is done at a significantly lower temperature (about 200 degrees Celsius). Compared to vitrified stones, resinoid stones are more effective at high speeds and therefore are great for large sharpening wheels. This method can creates softer stones (sometimes with a bouncy feeling), and is often used in the creation of super fine shiage toishi (or finishing stones). 

Magnesia method: A type of cement is added to main grain, and formed to shape. The material is then dried out at room temperature. This type of stone is often used to sharpen thin blades. Recently, magnesia stones have also been used for cutting and sharpening of non-steel items, such as other stones and glass. 


Main Types of Toishi Used Today

Arato (from about 60-600 grit): Used to form blade shape, repair major damage, and change the geometry (or angle) of cutting edge.

Nakato (around 1000 grit, but can range from 700-2000): Used to erase scratches from the arato, and touch up cutting edge (everyday maintenance). 

Shiageto (3000+ grit): Used refine the cutting edge and put a very sharp edge on the blade. 

\
Maintenance of Toishi



Vitrified stones should be washed thoroughly and stored after the usage (they can be stored in water). Resinoid and magnesia stones should be washed and dried thoroughly, and then must be stored in the shade. Also, resinoid and magnesia stones would be better kept if wrapped in cloth, and kept away from extremely dry or warm areas, since those conditions can change the bonding material in these stones.


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## idemhj (Mar 16, 2015)

Thanks Jon. Nice to know. I was wondering, do you know what was used in areas where natural abrasives were not available? Were such areas - like Denmark where i am from - dependant on import or could any stone be used?


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## Steampunk (Mar 16, 2015)

idemhj said:


> Thanks Jon. Nice to know. I was wondering, do you know what was used in areas where natural abrasives were not available? Were such areas - like Denmark where i am from - dependant on import or could any stone be used?



I am not Jon (Whose post was excellent, in case he is reading this.), but based upon my own research every country around the world has some form of local novaculite, slate, shale, sandstone, or other sedimentary rock that was and can be used for the sharpening of edge tools. In these, the abrasives are some form of silicate (Most often quartz, although Coticules are Garnet based.). Sadly, the names of most of these local sharpening stones have been lost to time, and only a few are known/quarried today... American Arkansas, Belgian Coticule, J-nats, Welsh Slate, German Thuringian Slate, Greek/Turkish oilstones, Lombardi Sandstone, etc are some of the more popular ones. In the straight-razor community, using 'found stones' (Pieces of slate, sandstone, or quartz with no known 'trade' name.) is growing in popularity. 

I don't know a lot about Danish sharpening stones, but I do know that the Danes (Like the Swedes, Finns, and Norwegians.) actually were known for their trade in whetstones / grinding stones during ancient times. I'm not sure as to the nature of these, but - at a guess based upon my understand of other stones from the region - were possibly some kind of Schist or Quartzite; maybe the latter, as Denmark is also known for its Flint. To learn more about native sharpening stones from Denmark, a good place to go would be museums which have very old farming and timber tools; often whetstones are displayed alongside these, and you might be able to figure out what kind of rock they are made from by looking at their pattern. Rock suitable for abrasive use is also sometimes mentioned in very old geological surveys, but these are hard to find, and often very dry/time consuming to sift through.

Hopefully this helps...

- Steampunk


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## Benuser (Mar 16, 2015)

Yeah, almost every region in Europe used to have its own natural stone for straight razor sharpening, which was a part of daily life in the pre WW2 time. Great for maintaining straight razors that are already in good shape, not for much more basic sharpening of kitchen knives, at much coarser grits. Especially a beginner should get fast stones, in which the synthetics excel.


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## bennypapa (Mar 16, 2015)

Thank you all.

How are the pores in coarse stones made?


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## panda (Mar 16, 2015)

like swiss cheese


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