Definition: MDF is the common name for Medium Density Fiberboard, an economical alternative to wood products. It is made by breaking down the fibers of wood and then reforming it with resin, pressure and heat.
The surface of MDF is hard and smooth. Moulding pieces of MDF can be purchased pre-primed, making final painting and installation easier and faster. It's not recommended to stain MDF mouldings, as there is no wood grain and the pieces look flat and uninteresting. Painting is recommended.
Moulding made of MDF is considerably less expensive than hardwood moulding and more stable than softwood moulding, making it a sensible alternative to real wood moulding.