Waterstone reality.... an Asagi of Indeterminate Origin (AIO), part 2

Slurry slurry slurry...... A funny sounding word in its own right, and it just gets MORE odd when you use it.

DMT #1200 slurry.

This is new territory for me, in terms of natural waterstones. My finest stone is a koppa (piece or splinter, sort of) Ozuku asagi, but this stone is finer yet and the action is smoother without being soft. Really easy to use and FAST, for its grit. I thought that the Ozuku was relatively fast, but THIS waterstone is about 4x faster! When I close my eyes and touch the Ozuku, I think of a blackboard, a writing slate, cold, sharp. When I touch this stone, I think..... cool, firm, a hard surface dusted with powder...

I want to try this stone with the ODC, but first I need to go back and do a bit more ground work..... and a reality check.

T=30sec. each stone (I'm not hardcore or anything).

This is the "ink" stone and the Ozuku asagi, using the ODC nagura. The slurry on Inky has oxidized to more of a gray/brown, but it was black a few seconds ago. The slurry of the Ozuku is still black. I am concentrating on polishing just the steel, so I am using a stroke parallel to the cutting edge.

When I use the ODC, I give the stone just a few swipes, barely enough to see. It is a VERY mild abrasive and as the ODC breaks down, it seems to expand about 10x in volume. Strange stuff.

T=15sec.

Even stranger..... With this stone, the slurry forms but only gets a bit darker, a gray tinge. "Normally" the ODC breaks down and quickly turns black with iron particles. With this stone, the slurry just sits there, as though the stone isn't working..... VERY interesting!

I THINK that what is happening is this......

A typical natural waterstone is composed of a range of particle sizes that are mostly larger than the particles of the ODC. The smaller ODC stuff acts as a cushion or filler, reducing the metals exposure to the abrasive. As the ODC degrades, more of the base stone's surface is exposed. In effect, the largest, most jagged particles are buffered by the ODC until they are worn down to a common size with the other abrasive grains.

 The slurry is the worn and degraded particles that have been dislodged from the parent stone. They both abrade the tool steel surface AND the stone surface as they get ever smaller.....

This stone behaves differently, with the ODC slurry at least. Magnify the last drawing 10x....

This stone seems to have an average particle size that is slightly SMALLER than that of the ODC. The ODC is masking or preventing the steel from making contact with most of the parent stone. Only a few particles are larger than the ODC, so they would be responsible for the slight darkening in color of the slurry. 

I feel that this is significant. I think that I have found the practical limits of the ODC nagura. This speaks well of both this stones quality AND the utility of the ODC nagura. WAY cool!

T=15 sec. 

No nagura and almost no slurry formation, but the stone doesn't feel super hard and is quite friendly. That dark patch on the upper left corner of the stone is basically all swarf. Amazing.

Full mirror on both steel (hagane) and iron (jigane). This blade is harder than most and somewhat special.

 Different blade, still good, but not AS hard. About as hard as my daily "users".

T=15 sec

I set the bevel to the stone, close my eyes, and slowly "guide" the blade. You can "feel" the stone remove the metal. I haven't felt ANY scratchy bits yet, not even the two dark spots. 

This bevel is reasonably flat and, if you look close, you will see some rust pitting but almost no scratches left over from other stones. 

Like I said, this is new sharpening stone territory for me, and I think that I know why.

Alex Gilmore at The Japan Blade  has a few stones that look similar, like this beauty....@$2,100!

Nakayama Maruka awasedo ttoishi

Here is my AIO again.

Very similar, especially the skin, although his are stamped and have a known provenance. If you go to his site (Item Nakayama #19), you can watch a video of his stone in action. The speed of metal removal is comparable to mine.... incredibly FAST!

I must admit to a certain degree of , not scepticism but maybe uncertainty, about how GOOD these old Toishi were/are. These old premium stones are an order of magnitude better than anything that I have used to date.

This is my A-team grit progression.... Inky, Ozuku, and AIO.

The bar has been raised.