This invention relates to a method of producing a tube from a glass that gives off undesirable vapors when heated in which glass cullet is placed into a horizontally disposed forming tube that is made of a material which is not wetted by the glass and has a lower coefficient of expansion (for instance the forming tube may be made of a borosilicate glass). The cullet is heated to melt the cullet while the forming tube rotates so that it coats the tube. The forming tube is cooled until the glass from the cullet has solidified as a tube. This tube may be used for making fibers in which a rod is subsequently inserted into this tube.