Abstract: The invention provides a method of manufacture of man-made vitreous fibers (MMVF) comprising: providing a fiberizing apparatus, wherein the fiberizing apparatus comprises: a set of at least three rotors each mounted for rotation about a different substantially horizontal axis; wherein each rotor has a driving means; rotating the rotors; wherein the first rotor rotates to give an acceleration field of from 25 to 60 km/s2 and the second and third rotors each rotate to give an acceleration field of at least 125 km/s2, providing a mineral melt, wherein the melt has a composition comprising the following, expressed by wt of oxides: SiO2 in an amount of from 33 to 45 wt %, Al2O3 in an amount of from 16 to 24 wt %, an amount of K2O and/or Na2O, an amount of CaO and/or MgO, wherein the ratio of the amount of Al2O3 to the amount of SiO2 is in the range 0.34-0.

Abstract: The invention provides a method of manufacture of man-made vitreous fibres (MMVF) comprising: providing a fiberising apparatus, wherein the fiberising apparatus comprises: a set of at least three rotors each mounted for rotation about a different substantially horizontal axis; wherein each rotor has a driving means; rotating the rotors; wherein the first rotor rotates to give an acceleration field of from 25 to 60 km/s2 and the second and third rotors each rotate to give an acceleration field of at least 125 km/s2, providing a mineral melt, wherein the melt has a composition comprising the following, expressed by wt of oxides: SiO2 in an amount of from 33 to 45 wt %, Al2O3 in an amount of from 16 to 24 wt %, an amount of K2O and/or Na2O, an amount of CaO and/or MgO, wherein the ratio of the amount of Al2O3 to the amount of SiO2 is in the range 0.34-0.