Hard glass (also known as high borosilicate glass): SiO2 (about 80%), sodium borate (12%) High temperature resistance, high pressure resistance, corrosion resistance, high mechanical strength, good thermal conductivity, temperature difference resistance, operating temperature<783K, annealing temperature 778-833K, can be heated to 873K in a short time, but the cooling annealing needs to be uniform and slow to reduce permanent stress Has good flame processing performance Commonly used for manufacturing beakers, flasks, pressure tubes, and complete experimental equipment It is a good material that is resistant to corrosion and ion pollution, such as domestically produced GG-17,95 glass.