A system and a method for dewatering an acoustical tile basemat comprising a continuously traveling wire, a device for depositing a dilute water slurry of solids including fiber and binder on the wire, a vacuum box below the wire for separating water from the solids deposited on the wire to form a basemat, a vacuum source, and a valve for cyclically connecting the vacuum source to the vacuum box at a cyclic rate that limits vacuum exposure to a length of the basemat newly arriving at the vacuum box to less than four inches per cycle.