MDF consists of wood fibers and glue or resin. The materials combine to form a type of hardboard under heat and pressure. Machines can easily create MDF. Plywood manufacturers glue several layers, or veneers, of thin hardwood or software between two parallel pieces of wood to create plywood. According to Design Technology, "[t]here is always an odd number of veneers and each ply is at a right angle to the one below, this gives the material its strength."
The appearance of plywood varies depending on the quality of materials used. Some people would consider certain plywood grains to be attractive while other types consist of knots in the wood. Medium density fiberboard does not contain knots, nor do the fine particles that make up the material give the impression of grain.
People will find MDF easy to cut, drill and otherwise manipulate without damaging the surface because it lacks both wood grain and knots. MDF pieces can be joined by dowels as well as traditional joints. Furthermore, a variety of surface treatments work well with MDF, including veneers, laminates, varnishes, oils and water-based paints. Plywood comes in a variety of strengths because manufacturers only need to add more veneers to the piece to increase the strength. Plywood is suitable for indoor and outdoor use, and the use of water-resistant glue increases the water resistance of the board.
When a person uses screws to attach MDF to other materials, it can split. Technology Design advises people working with MDF to use pilot holes and to keep the screws within 25mm in from the edge of the board. In addition to this, MDF can be quite heavy. Rick Christopherson explains that a "3/4" x 4' x 8' sheet can weigh as much as 70 to 90 pounds." Plywood may be susceptible to warping or buckling depending on the method of manufacturing and storage. Furthermore, plywood may not be ideal for all projects. Because of the method of manufacturing, thickness can vary by sheet; this is not the case with medium density fiberboard.
Cutting and sanding MDF can cause the material to release a substance known as urea formaldehyde. This substance can irritate the eyes and lungs. It is advisable to wear safety goggles and a mask when cutting medium density fiberboard and to work in a properly ventilated area. Because of this, workers will want to coat the board with a sealing product to prevent the urea formaldehyde from leeching.