Hardboard, also called high-density fiberboard, is a type of fiberboard, which is an engineered wood product. It is similar to particleboard and medium-density fiberboard, but is denser and much stronger and harder because it is made out of exploded wood fibers that have been highly compressed. Consequently, the density of hardboard is 31 lbs. or more per cubic foot and is usually about 50-65 lbs. per cubic foot. It differs from particle board in that the bonding of the wood fibers requires no additional materials, although resin is often added. Unlike particleboard, it will not split or crack. It is used in construction and furniture. Hardboard is produced in either a wet or dry process, which produce a panel called S1S or S2S respectively. The wet process leaves only one smooth side, but dry processed hardboard is smooth on both sides.
Unlike solid wood, hardboard is very Homogeneous with no grain. A wood veneer can be glued onto it to give the appearance of solid wood. Other overlays include formica and vinyl. It has many uses, such as a substrate. Unlike plywood and solid wood, it has no significant structural strength. It is used in construction, furniture, appliances, automobiles and cabinetry, and is popular among acrylic and oil painters as a painting surface due to its economical price (though it must be coated with gesso or canvas before use). It is also used as the final layer in many skateboard ramps and the half-pipe.
Tempered hardboard is hardboard that has been coated with a thin film of linseed oil and then baked; this gives it more water resistance, impact resistance, hardness, rigidity and tensile strength. An earlier tempering process involved immersing the board in linseed oil or tung oil until it was 5 to 6 percent saturated, and heating to 170° C (340° F). Tempered hardboard is used in construction siding.
Perforated hardboard, also called pegboard, is tempered hardboard that has rows of ¼" holes in it, into which hooks can be placed for hanging tools.