Party candles burning with coloured flames, time-lapse footage. These candles are made by impregnating the candle wicks with various metal salts. When lit, the candle flame burns in the characteristic colour of the metal salt used. For example, strontium chloride burns red, calcium carbonate burns orange, sodium chloride burns yellow, boric acid burns green, copper chloride burns blue, potassium chloride burns purple and magnesium sulphate burns white.