" About brass coloring "
The traditional colouring technique of “Takaoka Douki(copper)”, named “Nuka yaki shudo-shoku” was applied to each clock. The black satin colour with a speckled pattern is made by blackening after drawing out the pattern using a chemical and heating. The silver finish with a speckled pattern is achieved by applying pure silver plating. While the gas-bronze colour with a speckled pattern is produced by the green rust that forms when the clock face is exposed to ammonia gas.