Abstract: A glass composition is disclosed wherein the density and the refraction index and the dispersion value of light are equal to or higher than those of conventional lead-containing crystal glass while no lead is contained therein at all. The glass composition comprises 50 to 60% by weight of SiO.sub.2, 5 to 13% by weight of K.sub.2 O, 5 to 8% by weight of TiO.sub.2, 10 to 15% by weight of BaO, 5 to 10% by weight of ZnO, 3 to 10% by weight of Na.sub.2 O, 1 to 5% by weight of CaO, and 0.3 to 0.8% by weight of Sb.sub.2 O.sub.3.

Abstract: A glass article cutting method by which a glass article can be cut not only along a linear line but also along a curved line of a desired profile and can be cut comparatively readily even if the glass article has a concave or convex portion on a face thereof or even if the glass article has a complicated three-dimensional profile. A conductive coating material such as colloidal carbon is applied in a linear line or a curved line on a surface of a glass article to be cut, and a high voltage is applied from a pair of positive and negative electrodes to the line of the conductive coating material to energize the conductive coating material to generate heat thereby to cut the glass article by thermal stress caused by the heat.

Abstract: A glass vessel edge chamfering method and apparatus wherein heat energy can be controlled readily and chamfering of a glass vessel having a deformed profile, local chamfering and simultaneous processing of the opposite inner and outer sides of a lip of a vessel can be performed readily and besides the efficiency in consumption of energy necessary for chamfering for one glass vessel is improved so that a glass vessel can be processed efficiently in a short time. A pair of positive and negative electrodes are opposed in a predetermined spaced relationship to an edge of a glass vessel, and flame is blown from a pair of burners into gaps between the edge of the glass vessel and the electrodes while a high voltage is applied between the electrodes. Thereupon, electric current flows between the electrodes and the glass vessel by way of the flame and heats the glass vessel by Joule heat when the electric current flows through the glass vessel.