Air-formed mats emerge much thicker and softer than wetformed ones, and require more care in loading them into the press. Pressing in hydraulic presses From this point on, wet and dry process production procedures are virtually identical. Multiple hydraulic presses are heated by hot water, hot oil or steam. The combination of applied heat and pressure welds the fibers back together and produces properties unattainable in natural wood. The amount of press time, temperatures and pressures vary widely, depending on the process and physical properties of the board being produced.
All boards emerge from the hot presses with an extremely low moisture content.
Humidifying To prevent post-press warping or buckling, the boards are conveyed through a humidifier or stored on racks in a humidity chamber. This raises the moisture content to approximate atmospheric humidity. Although hardboards are humidified, they should be allowed to adjust to local atmospheric conditions before being installed. Trimming Tungsten carbide tipped saws trim boards to standard sizes. Sheets may be cut to any size a customer wants.