This defect is characterized by a chipped surface where small particles of wood have been broken or torn out. It occurs when the knives are cutting against the grain, often occurring around knots and swirls. This defect is characterized by groups of wood fibers not cutting cleanly at the surface and instead standing up above the surface. It is common in hardwoods such as aspen, basswood, cottonwood, and willow, with cells called gelatinous fibers in abnormal wood called tension wood. Apparently these cells are not strong enough to stand up while being cut, so they bend over and are not cut.
Control is obtained by using low moisture contents and sharp knives.
Possibly a larger rake angle will also help. However, when this fuzzy grain problem occurs, be aware of the associated problem of tension wood that causes severe warp, especially bow and crook, when the MC changes. This is a problem most often found in woods that have large differences in density within an annual ring. Usually the softer cells will be crushed. However, when these cells pick up moisture after machining, they will expand or spring back to their original shape creating the washboard surface.