Wood flour is a finely ground wood cellulose.
When the mesh size is above 20 mesh or below 850 microns, a product generally is considered to be wood flour. While wood flour CAN be made either wet or dry, most composite applications use extremely dry wood flour. The color range that you will find in wood flour is as broad as you will find in wood itself. This may range from almost white to brown. The product that you use in your composites should be as important to your supplier as it is to you.