Why are super-duty silica bricks used in the upper structures of glass-melting furnaces?

Super-duty silica bricks are used in the upper structures of glass-melting furnaces primarily because they possess particularly low impurity contents.1

In the context of industrial refractory materials, silica refractories are valued for their excellent load resistance at high temperatures and their resistance to abrasion. Because super-duty silica bricks contain fewer impurities than other grades, they provide the necessary stability and durability required for the demanding environment of a furnace's superstructure.1