Note to self-"Do not write book!"
Using natural stones to sharpen tools requires a willingness to experiment, to really pay attention to the act of rubbing a piece of metal against a rock and a lot of patience. Artificials ARE faster.
Sharpening like this is a composition. The right stone for the tool, not too hard, not too soft. A super hard sharpening stone works great until the abrasive finally wears down, and because the abrasive is soooo tightly held within the matrix, new grit doesn't get exposed. That's why old oilstones are so slow. They need to get "freshened" occasionally. Rubbing them on an old cinderblock works well, as does a piece of wet/dry sandpaper on a granite tile. Use a flat one.
Really hard finishing stones need a device to build up a slurry. Waterstones use water (duh!) as a lubricant. It helps the tool glide over the surface of the stone and washes away the metal bits (swarf) and also the microscopic fragments of stone that are shed continually. This...
If you use this stone without first building a slurry, you just rub the metal around without accomplishing much. The blade might get shiny from burnishing, but it won't get very sharp. You rub another stone, a nagura stone, on the rock to build up just the slightest hint of color (white in this case), and try again. It's like a completely different stone. You can tailor the nagura to the sharpening stone to get different results. A soft, coarse grit nagura on a hard, fine stone will start fast but as the nagura grains wear out, the finish will get progressively finer. All this without actually changing stones. Very fun and interesting for some.
Each tool being slightly different means that different stone combinations give different finishes or rather, the same stones work differently on different tools. If you want consistency, predictability or have a desire for plug-and-play, forget it.
|Or use a diamond plate to generate slurry.|
You can use a diamond plate to generate slurry. This eliminates one variable (kinda') in that the slurry is actually the same as the base stone. The diamond slurry tends to be a bit "harsher" though.
I have been on a stone testing tear for the last week or so. Just when I think that I have figured something out, I have the idea to try a different combination, or wetness, or change tools, or...something. My wife is the smart one, and while I have a VERY inquisitive bent, my methodology leaves a lot to be desired. Lets call this stuff anecdotal evidence, shall we?
Bring on then stones!