Sculptor’s whetstones - how to use them
These stones can be used to sharpen most sculptor's tools. The large concave stones sharpen the outside edges; the small convex stones sharpen inside edges. The illustration (upper left) shows how a stone is used.
Sharpening motion is elliptical, ie, back-and-forth and side-to-side simultaneously. Using the stone in this manner has the advantage that much larger tools can be sharpened than the size of the groove indicates.
Because Japanese stones are soft, their shapes can be changed using 80 to 120 grit wet-or-dry sandpaper. This is especially useful if you wish to use the convex stones to sharpen the inside of a V-tool, for example, and the stone does not have the proper shape. You only need to pass the stone over a piece of wet-or-dry sandpaper mounted on a flat work surface (ie, glass, MDO, saw table, etc.) to achieve the desired shape.
If you wish to shape the stone for a specific tool, wrap wet-or-dry sandpaper around a dowel having the approximate radius of the tool, and enlarge the groove to fit.
The backs of concave stones can also be used to sharpen chisels.