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The Carl Zeiss Foundation of Mainz in Germany wants the optics industry to
stop polluting landfills and tips with leaded glass (GB 2349639). Lead oxide is
traditionally added to glass to improve its optical properties and make it
easier to work with. But discarded lenses containing lead are an environmental
hazard. The foundation claims that a finely balanced mix of silica and boric
oxide has the same benefits as the lead. Adding oxides of barium, calcium and
aluminium further improves melting properties and transmission of blue
light.