low density mineral wool structural panels are manufactured by frothing a dilute aqueous dispersion of mineral wool , lightweight aggregate , binder and a small amount of amine - based cationic surfactant onto a non - woven scrim cover sheet , dewatering the mass and drying it . the froth is a mass of weakly resilient bubbles that rapidly dewater and burst to concentrate the solids in the mass . the bubbles are readily broken without loss of the voided structural configuration by a first application of brief pulses of high vacuum followed by further dewatering under vacuum and rapid drying by passing large volumes of air through the voided mass without collapse of the structure to result in lightweight structural mineral wool panels .