TotalBoat Penetrating Epoxy will not have a very deep penetration into MDF (medium density fiberboard). Penetrating Epoxy will, however, act as a great sealer for the board material. Follow the Penetrating Epoxy's surface preparation for wood, and sand the surface prior to applying. Medium density fiberboard is essentially wood fibers, a glue, and a paraffin wax that are heated and pressed together to form a board material.