Striation-free, refractory-type glass tubing can be manufactured by placing particulate, crystalline, refractory materials in a tube of refractory glass having a sealed end. The tube is evacuated to withdraw gases and the vacuum is maintained. The sealed end of the tube is heated to its softening point and the particulate materials contained therein will melt, thereby converting these materials into a vitreous condition. Softened pieces are then broken off and substantially gas-free bodies of vitreous, refractory glasses having substantially no reentrant portions are formed. The majority of the surfaces are smooth and rounded. These bodies are then fed into a melter of conventional design at atmospheric pressure and substantially striation-free, refractory-type tubing is drawn.