Q: We seem to notice some fine fuzz on the surfaces of our oak and yellow-poplar lumber after sanding. It seems to be in streaks or in certain pieces of wood, but not others. It also comes and goes; some days it is worse than others. The fuzz is a real problem if we let it go into the finishing room. Any ideas?
A: The wood fibers are usually quite strong and can be cut cleanly by the minerals in the sandpaper. However, if the sandpaper is worn out, then the mineral is very dull. Dull sandpaper will push the fibers over rather than cut them off. If you look closely at the surfaces right after sanding, you will notice the fuzz from these uncut, pushed-over fibers.
Things will be worse when these pushed-over fibers are subjected to water (such as from a water-based finish) or high humidity. This will cause them to "stand at attention" and the fuzz will look terrible. This fuzz problem can also be caused if the fiber is exceptionally weak. The weak wood fibers are a result of a special growth feature in wood called tension wood (in hardwoods only). With tension wood, the wood is typically 10 percent or more lighter in weight (and is proportionally weaker, too). Except for poor machining or low density, tension wood is hard to detect. If you suspect that you have tension wood, you can use glue sizing or sanding sealer to coat and stiffen the fibers before sanding. However, sharp sandpaper will probably be an acceptable solution to successful machining of this special fiber.
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