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Why does pure silica glass require extremely high melting temperatures?

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Pure silica glass (fused silica) requires extremely high melting temperatures because the melting point of crystalline silica—the raw material typically found as sand or quartz—exceeds 1,700 °C (3,092 °F).1

Attaining these temperatures is technically demanding and expensive. In industrial glass manufacturing, this high thermal requirement is the primary reason why fluxing agents, such as sodium oxide derived from sodium carbonate, are added to the mixture. These fluxes disrupt the rigid network of SiO4 tetrahedra, significantly lowering the melting temperature to a more manageable range, such as 850 °C.123

Because of the extreme energy costs associated with melting pure silica, its use is generally reserved for specialized applications where its unique properties—such as high chemical inertness and the ability to withstand sudden temperature changes—justify the expense.1