Questions on medium density fiberboard (MDF) and sticker shadows are answered. MDF is a fiber product. That is, the wood is defiberized, making the wood into individual fibers or clumps of several fibers. By controlling what goes into the product and the pressures and temperatures used, MDF will have a fairly wide range of properties. A raised glueline most commonly results because the wood between the gluelines is shrinking while the glueline itself is not. What causes the shrinkage in wood is that the wood is wetter than its environment, so the wood dries and this means that the wood will shrink. The key to understanding the cause of reverse sticker shadow is that when drying lumber, differences in drying rates will often result in differences in color, especially with the white colored woods.