Chemically speaking, quartz glass is a particularly durable material—it can withstand major fluctuations in temperature, allows UV radiation through, and has a high dielectric strength. These characteristics are highly prized by Heraeus Noblelight production in Alzenau, as quartz glass tubes are used as lamp bodies in the manufacture of UV lamps. But because the outer layer still may have a certain degree of impurities, the tubes must be cleaned before they can be used, which is a real challenge with such a resistant material.
Heraeus Noblelight previously only had one option for this, hydrofluoric acid (an aqueous solution of hydrogen fluoride). “Hydrofluoric acid is so corrosive that it etches away the top layers of the quartz glass, removing even the smallest impurity,” says Andreas Adam, a production engineer at Heraeus Noblelight. “Of course that also makes it an enormous safety risk.” Hydrofluoric acid is a contact poison and can be fatal even after a palm-sized chemical burn. Production has comprehensive security procedures to prevent serious accidents, but near accidents or even minor injuries cannot be ruled out when dealing with such a corrosive substance, according to Adam.