A method for heating an elongate silica cylinder for use in the manufacturing of optical fibers, the method preferably being for collapsing an elongate hollow silica cylinder, to form a core-rod for optical fibers; the method for heating comprising: - providing a heating device comprising: * an elongate cavity extending in an axial direction of the device, arranged for allowing the cylinder to extend through the cavity in use, * an elongate cylindrical liner having a cylindrical wall, said liner being made of carbon, extending in the axial direction and bounding the cavity with the cylindrical wall * a heating element for heating the elongate silica cylinder in use, the heating element being provided in an annular heating element space, said heating element surrounding at least a part of the liner, the cylindrical wall of the liner separating the heating element space from the cavity, the heating element space on an outer side bounded by a further surrounding wall part of a frame portion of the device, * a gas flushing device for effecting a flow of a gas at least through the heating element space, - providing the elongate silica cylinder such that it extends through the cavity of the heating device, - heating the elongate silica cylinder locally beyond the softening temperature by means of generating heat using the heating element of the heating device, - effecting the flow of the gas at least through the heating element space by means of the gas flushing device during the heating step, wherein the flow of gas comprises at least argon gas and nitrogen gas. - providing a heating device comprising: * an elongate cavity extending in an axial direction of the device, arranged for allowing the cylinder to extend through the cavity in use, * an elongate cylindrical liner having a cylindrical wall, said liner being made of carbon, extending in the axial direction and bounding the cavity with the cylindrical wall * a heating element for heating the elongate silica cylinder in use, the heating element being provided in an annular heating element space, said heating element surrounding at least a part of the liner, the cylindrical wall of the liner separating the heating element space from the cavity, the heating element space on an outer side bounded by a further surrounding wall part of a frame portion of the device, * a gas flushing device for effecting a flow of a gas at least through the heating element space, * an elongate cavity extending in an axial direction of the device, arranged for allowing the cylinder to extend through the cavity in use, * an elongate cylindrical liner having a cylindrical wall, said liner being made of carbon, extending in the axial direction and bounding the cavity with the cylindrical wall * a heating element for heating the elongate silica cylinder in use, the heating element being provided in an annular heating element space, said heating element surrounding at least a part of the liner, the cylindrical wall of the liner separating the heating element space from the cavity, the heating element space on an outer side bounded by a further surrounding wall part of a frame portion of the device, * a gas flushing device for effecting a flow of a gas at least through the heating element space, - providing the elongate silica cylinder such that it extends through the cavity of the heating device, - heating the elongate silica cylinder locally beyond the softening temperature by means of generating heat using the heating element of the heating device, - effecting the flow of the gas at least through the heating element space by means of the gas flushing device during the heating step, wherein the flow of gas comprises at least argon gas and nitrogen gas.