Shimizu used copper carbonate in the Pyrotechnica-6 study’s 867- 872 formulas, which all produced “excellent blue” color. His 845 – 849 formulas are similar, except copper oxide was used to produce “excellent blue”. So, in the above formula, either copper compound may be used. Copper carbonate produces a star which burns for twice as long as a star made with copper oxide, though. Jim Widmann states that an additional 1.5% fine MgAI may be added for greater brightness.