Oil Stones differ from water stones in that they require the use of honing oil to float the swarf (metal particles). Also, these stones are commonly made from one of three different materials consisting of Novaculite, Aluminum Oxide (Corundum), or Silicon Carbide (Carborundum) and they all use oil to lubricate the stone and suspend the swarf in order to prevent the stone from becoming clogged. Also, while Novaculite and Coticule are the most traditional types of oil stones, there are also synthetic oil stones made by the Norton abrasives company called “India Oil Stones”.
Heres why I wasn't impressed at first. I only used it for a few minutes on each side, which resulted in nothing. I watched a video online with a master chef using his stone, and he sharpened his knife for 10 minutes on each stone before moving up to a finer grit. I took this hint, and used sharpened my knife on each side of this stone for 10 minutes, which led to perfection.
To take off the fine scratches and the burr left by coarser stones, and polish the surface, one can use stones starting around 2000 grain. Above that there is theoretically no upper limit, but at the same time stones above about #10000 provide no measurable practical improvement in the edge. It is also interesting to note that above #8000 grit, there is no Japanese measurement standard. With all the stones labelled as having a finer grit, one simply has to take the manufacturer’s word for it.
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