On Tuesday, the Vatican press office revealed the composition of the colored smoke used during the conclave to signal the results of the voting. Earlier, a Vatican spokesman had said only that the smoke was made “from several different elements.”
Both recipes are fairly standard pyrotechnical formulas. The white smoke, used to announce the election of a new pope, combines potassium chlorate, milk sugar (which serves as an easily ignitable fuel) and pine rosin, Vatican officials said in a statement. The black smoke, which was used Tuesday evening to signal that no one in the first round of balloting received the necessary two-thirds vote of the 115 cardinals, uses potassium perchlorate and anthracene (a component of coal tar), with sulfur as the fuel. Potassium chlorate and perchlorate are related compounds, but perchlorate is preferred in some formulations because it is more stable and safer.
Milk sugar and pine versus coal and sulfur: There’s a simple beauty to the Vatican’s chemistry.