Glass typically has a tensile strength of 7 megapascals (1,000 psi).[1] However, the theoretical upper bound on its strength is orders of magnitude higher: 17 gigapascals (2,500,000 psi). This high value is due to the strong chemical Si–O bonds of silicon dioxide. Imperfections of the glass, such as bubbles, and in particular surface flaws, such as scratches, have a great effect on the strength of glass and decrease it even more than for other brittle materials.[2][1] The chemical composition of the glass also impacts its tensile strength.[3] The processes of thermal and chemical toughening can increase the tensile strength of glass.[4]