The chemistry of the Papal Conclave’s smoke signals

This week, Cardinals of the Catholic Church are gathered in the Vatican to select a new Pope. Traditionally, smoke signals are used to indicate the results of their ballots. Black smoke indicates no decision has been made, while white smoke shows that a new Pope has been chosen.

This graphic takes a look at how the different smoke colours are generated. The Vatican does actually have an official recipe for both smoke colours, after ambiguous colours caused confusion in previous decades.

For more details on the smoke components and the historical background, check out this excellent summary from Professor Mark Lorch in The Conversation.