Medium Density Fiberboard (MDF) is a composite sheet product. Prior to refining, the wood fiber to be formed into MDF is “cooked” in a moderate pressure steam vessel (digester). This step changes the wood chemically and physically; making the fiber content of MDF less susceptible to the influences of moisture and brittleness. During the refining step, the wood is rubbed into fiber bundles, which will orientate into a super-strong random mat. A resin binder is added and the panel is hot pressed. The final phase includes sanding and sawing.