<Li> Larger Roman candles (three - inch diameter or more) usually add more lift to the highest layers and less to the lower layers in order to cause the stars to lift to the same altitude . This is due to the shorter length of tube available for accelerating the higher stars (see firearms internal ballistics). </Li> <Li> Some very large Roman candles load comet shells instead of stars . </Li> <P> The stars of Roman candles can be found in a variety of colors . Colors are manipulated by adding compounds which, when ignited, release visible light and other radiation . For example, when potassium perchlorate (KClO) is used as an oxidizer, chemical reactions involving the dissociated elements of the perchlorate--potassium and chlorine ions--create barium compounds which emit green light (especially BaCl). The potassium compounds formed by this reaction emit mostly near - infrared light, and so they do not affect the color of the star in a significant way . This reaction occurs at temperatures exceeding 2500 ° C (4532 ° F), at which the ions in KCl dissociate into free K and Cl . Alternatively, SrCO can be added to the candle to produce a red or pink star, but, because it does not oxidize, more oxidizers and fuels must be added to sustain combustion . During combustion, various strontium compounds (especially Sr (OH) emit red light, most of which is between 506 and 722 nm in wavelength . </P>

Where did the phrase roman candle come from