Glass wool is made from a combination of natural and recycled glass that has been transformed into fibers at a temperature of 1450 degrees Celsius. The thickness of these fibers is between 6 and 7 microns, which are woven together in the glass wool production process. This tufting of fibers causes the creation of millions of holes (air pockets) in glass wool, which create the insulating nature of glass wool by keeping air in it.