In 1996/97 working together with the laboratories from the University in Liege, we had the geological deposits of rock close to the traditional "Yellow Whetstone" closely analysed. With amazing results. We discovered a high quality whetstone with identical sharpening properties as the "Yellow Whetstone" but only blue in colour, which derives from deposits of iron oxide. Almost 30% of it's weight is garnet, as opposed to the yellow which has approx. 35-40% garnet, this means it works just a little slower.
The thickness of the Belgian Blue Whetstone is between 13 and 16 mm and unlike the Coticule, the BBW is a single side stone. It has a grit of ca. 4000 and contains 20 to 30% garnets which allow the stone to whet at a fast speed. The colour of the BBW is blue-grey.
The biggest advantage of the "Blue Whetstone" is the size of the deposits, in layers from 15-20 cm of useable material, which means large bench stones can be cut.
Beyond this these stones are suitable for making profile slipstones and, in contrast to other, harder slip stones, the "Blue Stone" is soft enough to be shaped by using sandpaper to create profiles for individual use.
Pictured is the 200mmx75mm