Abstract: An electrical melting technique for glass, more specifically, a technique wherein the conductivity of the molten glass is used to develop the energy necessary to melt the raw materials. Energy is dissipated by a Joule effect into the molten mass from vertical plunging electrodes, with the composition to be melted being spread in a uniform layer on the surface of the bath. The electrodes are arranged at a distance from the refractory walls of the tank, with the distance separating the electrode from the closest lateral wall being at least half that separating two adjacent electrodes and the position of the level of the maximum temperature being regulated by the depth of immersion of the electrodes.

Abstract: Glass fibers having the following constituents in the ranges of proportions indicated: SiO.sub.2, 57-70 wt. %; Al.sub.2 O.sub.3, 2-7 wt. %; CaO, 5-10 wt. %; MgO, 0-4 wt. %; B.sub.2 O.sub.3, 0-4.5 wt. %; and F, 0.5-4 wt. %; and wherein B.sub.2 O.sub.3 and F are present in amounts according to the relationship:3.ltoreq.B.sub.2 O.sub.3 +1.5 F.ltoreq.6.5and wherein the fibers also contain the alkali oxides Na.sub.2 O and K.sub.2 O, in amounts according to the relationship:16 wt. %<Na.sub.2 O+K.sub.2 O<20 wt. %.The glass fibers are used advantageously in thermal and/or acoustic insulation.