Density development in foam forming: Wet pressing dynamics

The compression behaviour of both foam and water formed wet sheets was studied in the laboratory. The development of sheet thickness was followed for different pressing dynamics including both short and long pulses. The immediate recovery of sheet thickness after the first short pressing pulse was clearly better for foam than for water. The bulk advantage of foam forming gradually reduced as the number of pressing pulses increased. The solids content after wet pressing became higher for foam than water forming. The differences in sheet density and dewatering for the two forming methods should be taken into account when developing industrial processes for lightweight fibre-based products.