37432899___Straight_Razor_Place_Library__Comments
[Name] Belgian blue (with slurry) [Grit (approx.)] 4k [Typical use] Sharpening [Comments] 
The BBW, also known as the Belgian Blue Whetstone, is mined/quarried in close proximity to the yellow cotcule. In past years the bbw was mainly used for cobblestones, building blocks and such utilitarian purposes. At one time the reinforced backing glued to yellow coticules was the bbw. Later slate became the reinforcement for the yellow coticule when the bbw became a more valuable commodity due to the relatively recent recognition of it's honing properties. Coticule expert and SRP member Bart Torfs of Belgium says that while the yellow is composed of 45% garnet content by volume the BBW has approximately half at 25% garnet content by volume of the rock. This explains the yellows superior performance in sharpening with and without slurry. According to Bart, of http://www.coticule.be/ , using a slurry is the most effective way of sharpening with the blue. This releases the garnets more freely for more aggressive cutting. While the use of slurry with the yellow is much more aggressive due to the higher garnet content, slurry with the lesser garnet content of the blue seems to yield a sharp edge more easily than a slurry with the yellow. The yellow's slurry being so much more highly concentrated with garnet that it can have a dulling effect on the thin edge of the razor. Using the blue in conjunction with the yellow whether in a natural combo, glued or as two independent stones, many honers find using the blue with a thick slurry to sharpen and the yellow with water only to finish to be an effective way to hone their razors. A thick slurry on the yellow is more effective at bevel correction while in the hands of an expert diluting the yellow's slurry can bring the edge to the same level of sharpness as the blue and then go on to water only for the same finish. Still the blue has it's place and is an effective stone when used with slurry. Again it is difficult to give a grit rating to a natural stone but it seems that the general consensus of those who insist on doing so rates the BBW in the neighborhood of 4k. It is commonly believed that due to the relatively sparse distribution of garnet the blue is less effective without utilizing the slurry.
Hones - comparison table - Straight Razor Place Library
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