Guy's:
May I add a bit of correction. Tonkin Cane rarely comes is diameters larger than 2 1/2" at the butt end, its the cane that fly rod makers use. Too my knowledge nobody is making bows from it. What is commonly known as "Tree cane" is what bamboo bows are made of. It comes in diameters of 6 or more inches in diameter. You can not grind a flat lamination wide enough from 2 1/2" cane to make a bow. As far as "dirty" cane is concerned its nothing more than water stain, some real interesting patterns are found in that type of cane and make a beautiful bow under clear glass.
Bob