GRIT TEST PROCEDURE
I developed this Grit Test Procedure as a home style scientific system in an attempt to photographically capture for comparative
purposes, the scratch lines or scratch pattern left on a Japanese steel kanna blade by different sharpening stones. I designed
this method so that almost anyone could replicate the method themselves with a minimal amount of cash output. The actual grit
particle size of Japanese finishing stones- tennen toishi, has been a topic of discussion that has been based primarily on the
opinion of the owner in relation to how the stone feels, or how "sharp" the blade gets after using the stone in question. I am not
suggesting that the owner of any stones in question does not have an excellent perception of the cutting qualities of their stones,
but instead I have been simply looking for some way that 2 parties can have an intelligent conversation using visual aids.
Because I do not have the actual ability to measure small scratches I choose to use the Sharpton 30,000 grit Glass Stone, product
number 50403, as a jumping off reference point for these photo comparisons. This Shapton is a stone that is readily available
and at 30K it represents the finest grit particle normally used by woodworkers in a synthetic man made stone formula. Conversely,
the Bushnell Portascope I use is also available and can be purchased on the internet for as little as $24.00. It is similar to what is
called a Dissection Microscope where the specimen area has room to place a larger object and the illumination comes from
above or the sides. My camera is an older Olympus with a optical zoom. I illuminate my subject from one side only with a simple
halogen table lamp. Any lamp or camera will work as will any microscope that will allow the above requirements but in order for
the scratches to be seen and photographed the light source must come from the side or approximately at 90 degrees to the
scratches. The software I use in my computer is a 1999 version of Adobe Photoshop Deluxe, it came free with my Epson printer
(long gone) and I have used this program in all of my computers since until I upgraded to the Microscope Vista model. I now use
the Microsoft Windows Picture along with the Picasa program.
The photos are based on a scale of 1 centimeter wide. For my purposes this is close enough and when magnified on a 25cm.
wide computer screen it represents a magnification of about 25 times. The camera is set to the macro-zoom to get the close
shots, and the photos are then reduced a small bit in the computer. My intentions are to compare the scratch patterns on a given
blade, not to delve into the microscopic make up of the blades metal composition, so this power seems good enough for those
purposes. The lack of resolution, depth of field and lack of focus from side to side is more than likely from the poor optics of the
Portoscope. All of the equipment could be upgraded, but at what cost. For my money, this is working OK for now.
Originally the blade I was using was a 1940's-50's Ishido Teruhide Swedish Blue Steel 70mm kanna blade. I am now using a
1950's Hitachi 70mm Super Blue Steel blade made using the VIM vacuum induction method. The blade is marked on the front
HOJOJI, a historical reference, specifically to a Kyoto Buddhist temple, and sometimes poetically used by Osaka/Miki area blade
makers, and on the back SHINKU meaning vacuum. I like this blade because the reference points I am using for scale in the soft
iron jigane are deep and prominent and will hopefully appear through many sharpening.
The light source I use is from the left side, and at a parallel to the blades cutting edge while being at a direct right angle to the
scratch pattern produced from the sharpening stone. The light may need to be adjusted by a degree or two in order to draw out the
reflective brightness of the scratches but you should have the light low to create a racking effect over the scratches to help
illuminate the ridges while keeping the valleys in shadow. I use the same set up for each photo including the photo after using the
Shapton stones.
I trust that the following photos will fill in any blanks I have not dealt with in this short description above. As you can see there is no
mystery to these tests, and they are simple enough so that very little information can be falsified or manipulated. Any suggestions
and comments will be greatly appreciated.
I developed this Grit Test Procedure as a home style scientific system in an attempt to photographically capture for comparative
purposes, the scratch lines or scratch pattern left on a Japanese steel kanna blade by different sharpening stones. I designed
this method so that almost anyone could replicate the method themselves with a minimal amount of cash output. The actual grit
particle size of Japanese finishing stones- tennen toishi, has been a topic of discussion that has been based primarily on the
opinion of the owner in relation to how the stone feels, or how "sharp" the blade gets after using the stone in question. I am not
suggesting that the owner of any stones in question does not have an excellent perception of the cutting qualities of their stones,
but instead I have been simply looking for some way that 2 parties can have an intelligent conversation using visual aids.
Because I do not have the actual ability to measure small scratches I choose to use the Sharpton 30,000 grit Glass Stone, product
number 50403, as a jumping off reference point for these photo comparisons. This Shapton is a stone that is readily available
and at 30K it represents the finest grit particle normally used by woodworkers in a synthetic man made stone formula. Conversely,
the Bushnell Portascope I use is also available and can be purchased on the internet for as little as $24.00. It is similar to what is
called a Dissection Microscope where the specimen area has room to place a larger object and the illumination comes from
above or the sides. My camera is an older Olympus with a optical zoom. I illuminate my subject from one side only with a simple
halogen table lamp. Any lamp or camera will work as will any microscope that will allow the above requirements but in order for
the scratches to be seen and photographed the light source must come from the side or approximately at 90 degrees to the
scratches. The software I use in my computer is a 1999 version of Adobe Photoshop Deluxe, it came free with my Epson printer
(long gone) and I have used this program in all of my computers since until I upgraded to the Microscope Vista model. I now use
the Microsoft Windows Picture along with the Picasa program.
The photos are based on a scale of 1 centimeter wide. For my purposes this is close enough and when magnified on a 25cm.
wide computer screen it represents a magnification of about 25 times. The camera is set to the macro-zoom to get the close
shots, and the photos are then reduced a small bit in the computer. My intentions are to compare the scratch patterns on a given
blade, not to delve into the microscopic make up of the blades metal composition, so this power seems good enough for those
purposes. The lack of resolution, depth of field and lack of focus from side to side is more than likely from the poor optics of the
Portoscope. All of the equipment could be upgraded, but at what cost. For my money, this is working OK for now.
Originally the blade I was using was a 1940's-50's Ishido Teruhide Swedish Blue Steel 70mm kanna blade. I am now using a
1950's Hitachi 70mm Super Blue Steel blade made using the VIM vacuum induction method. The blade is marked on the front
HOJOJI, a historical reference, specifically to a Kyoto Buddhist temple, and sometimes poetically used by Osaka/Miki area blade
makers, and on the back SHINKU meaning vacuum. I like this blade because the reference points I am using for scale in the soft
iron jigane are deep and prominent and will hopefully appear through many sharpening.
The light source I use is from the left side, and at a parallel to the blades cutting edge while being at a direct right angle to the
scratch pattern produced from the sharpening stone. The light may need to be adjusted by a degree or two in order to draw out the
reflective brightness of the scratches but you should have the light low to create a racking effect over the scratches to help
illuminate the ridges while keeping the valleys in shadow. I use the same set up for each photo including the photo after using the
Shapton stones.
I trust that the following photos will fill in any blanks I have not dealt with in this short description above. As you can see there is no
mystery to these tests, and they are simple enough so that very little information can be falsified or manipulated. Any suggestions
and comments will be greatly appreciated.