The secret of purple glass is based on the fact that the harmful spectral domain of light is filtered and removed. The protective effect of violet glass has been confirmed by biophotonic measurements by Dr. Hugo Niggli of the Institute for Biophysics of Prof. Fritz Popp since 1996. Another series of tests, performed in 1997 at the institute by Dr. Dieter Knapp, impressively confirms the effectiveness of purple glass.
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