Particle board has been in use since the 1940s, often used in place of the more expensive plywood as subflooring or instead of natural hardwoods in furniture manufacturing. At one point in its history, however, this material was considered an expensive designer board, reserved for use in exclusive homes and upscale furniture factories. Modern particle board is now made primarily by combining discarded wood shavings, chips and sawdust with a strong resin and pressing the mixture into serviceable boards and planks.
The process of making this material begins with real wood. Most manufacturers use waste wood products collected from commercial woodworking factories, although some virgin wood may be used as well. All of this recycled wood fiber and sawdust is stored in large containers before being processed into boards.
The wood bits are usually dried, then sorted to eliminate overly large or small pieces. Once this mechanical sorting has been completed, the acceptable wood fibers move by conveyor belt to a blending hopper. Along the way, several overhead nozzles spray the wood fibers with a strong liquid resin or glue. Several different forms of resin may be used, depending on the specific quality of particle board desired. Historically, formaldehyde-based resins were most common, although in recent years many manufacturers in the US have moved to low-emission resins or those that do not contain any formaldehyde.
The resin-soaked wood is then blended to form a consistent paste. This combination is piped into a forming machine, which presses out a sheet of uncured particle board. The formed panels are then pressed down for easier transportation to the final curing ovens. Individual sheets are held under pressure as the air around them is superheated. This allows the resin to harden and form a very strong bond with the wood fibers.
Some forms of particle board are left in this rough state for use in flooring and other projects in which the panels will not be visible. In situations in which the appearance of the product is a concern, thin strips of real wood, called veneers, may be added to the surface of the board. Furniture manufacturers often use veneer-covered particle board as a cheaper alternative to natural hardwoods. Many assemble-it-yourself desks and other home furnishings may also be made from veneered particle board.