Naniwa Professional stones, formerly called Chosera are Naniwa’s top shelf series loved for their fast consistent finishes. These are excellent for wide and single bevel knives as well as double bevel.
If you find yourself working for more than 5 minutes with a 1000 grit stone chances are your sharpening will improve by adding a coarse stone. This 400 stone is great for quickly bringing back dull edges or for helping in thinning and repair. For very drastic chips or sculptural overhauls of thick blades a coarser stone might be necessary but this stone does a huge amount of work. We found it cuts fastest with a thin watery mud and a bit shallower and slower with a dry layer of slurry. For longest lift be sure to flatten during heavy projects to avoid digging deep furrows into the stone.
Naniwa Professional stones have a high concentration of a very evenly graded grit bonded in a magnesia binder, they are on the boundary between a hard and soft stone leaning on the harder end.
Because magnesia binder can dissolve we recommend a short soak of 15 minutes only. The mud generated during sharpening will add cutting material when sharpening wide surfaces of single bevel knives or thinning wide bevel knives, during sharpening small amounts of water can be added to help adjust the sharpening feel