The manufacture of glass is carried out in a special furnace at about 1550°C/2822°F (E-glass) using finely ground raw materials from carefully selected quarries. The glass leaves the furnace at a very high temperature and is used to feed bushings (blocks pierced with hundreds of holes) of platinum alloy. The basic glass strand is made by forming. Forming is achieved by drawing the molten glass flowing from the holes of the bushing at high speed. This forms between fifty and several hundred filaments. These filaments are defined by their diameters: from 5 to 13 microns (1µm = 1/1000 mm). The individual filaments receive a coating of size at the forming stage, immediately after they leave the bushing. This size, made up of organic products dispersed in water, is designed to give the glass strand certain characteristics necessary for the end application.