Core-sheath glass fibers

1. Field of the Invention Provided is a glass fiber prepared by combining two glasses, preferably at least one of which is biosoluble, in a core/sheath arrangement. Such an arrangement can provide fibers potentially stronger than those of single glasses, while also having a permanent twist or curl to impart improved loft and recovery to blankets or mats comprised of them. Preferably, the core is offset from the center of the fiber. In one embodiment, the glass fibers of the present invention comprise a core and a sheath, where the core glass of the structure contracts as it cools to a greater extent than the sheath glass of the structure. Benefits are achieved in this manner, preferably with regard to biosoluble fibers.