Stitchawl - coconut shell contains 3 to 5% silicate by weight. It rather difficult to strop on a spherical object but at least its hard surface keep convexing to a minimum. I stropped a few of my knives using coconut shell, was tricky but had about the same result as using horse leather. Coconuts from river delta region contain finer silicate.
ALL living things contain silicates. Silicates start out in the soil in the ground. Plants (with roots that soak up nutrients from the ground) contain the most silicates of all living things. Animals that eat the plants retain a lot of the silicates which is why A) leather works so well for stropping but B) stropping on your own (or someone else's) palm will have an effect too! Certain grasses contain higher concentrations of silicates than others, and animals that eat those grasses have a higher concentration of silicates in their hide. Oats have a higher silicate concentration than garden grass, so animals feed on oats or on oat grasses or hay will have a higher concentration than animals that have grazed the ordinary grasses in the North 40.
It makes perfect sense to me that stropping on a coconut shell would be great! And for those of us who live in areas where we can get fresh green cocounts (rather than the brown shaggy ones in supermarkets) this would be a perfect stropping medium! The larger Thai coconuts have broad 3"-4" flat surfaces on many of them!
How do you feel about this conclusion from Dr. Verhoeven and his
sharpening study:
The Verhoeven study was a brilliant work in many ways, but not in all of them. Verhoeven stated that stropping on leather didn't give him any better edge. While you and I may not have the education that Dr. Verhoeven had, nor the tools of his laboratory, you and I both
KNOW FROM EXPERIENCE that stropping on bare leather improves the edge. Repeated experiential knowledge with the exact same results performed by hundreds of thousands of people over hundreds of years (knife hobbyists, wood carvers, and most especially... barbers have all PROVED time and time again that Dr. Verhoeven's result was flawed.
However... and this is very important... Stropping a dull knife on bare leather is an exercise in futility unless you are willing to spend several years working at it.
YOU MUST START WITH A VERY SHARP EDGE BEFORE YOU STROP ON BARE LEATHER. In that way, the sharp edge can become sharper with just a few strokes on a strop.
We all know the CrO is sharper & harder than silicate. CrO abrade, Silicate probably burnish more than abrading.
Er.... It's important to keep in mind that
there are a LOT of DIFFERENT silicates involved here. Some are softer than CrO, but some are harder too. Silicate is just an overall term for a mineral that contain silicon and oxygen. Even Talc is a silicate, just not one that's very effective for our needs in a strop. Quartz, Feldspar, Zirconium, Garnet, Flints,.... all in silicate combination...
the list is endless! These are what is getting the work done for us when we strop.
Stitchawl
