With the passing of Pope Francis, a group of Catholic cardinals will now meet to pick a new pope in what’s called a papal conclave. Sequestered in the Sistine Chapel, the 135 cardinals will cast votes to elect a new pope. Their ballots are burned after each round of voting so the cardinals’ choices remain secret. Updates from within the conclave come not from press conferences, but from the chapel’s chimney. For a little more than a century, the cardinals have signaled their progress by sending colored smoke up the chapel chimney. Black smoke signifies that the vote didn’t produce a pope, and white smoke indicates that a decision has been reached. When the tradition began, the light smoke was produced by the burning ballots and some dry straw, while the darker smoke was produced by the burning ballots and wet straw. In 2005, the Vatican went high-tech and introduced an “auxiliary smoke-emitting device” that was fed chemical cartridges that could produce clearly colored smoke for up to six minutes. The black smoke is made from a mixture of potassium perchlorate (a salt commonly used as an oxidizer in colored fireworks and other pyrotechnics), anthracene (a component of coal tar) and sulfur. The white smoke is produced by mixing potassium chlorate (used in fireworks and smoke bombs), lactose (the sugar found in cow’s milk), and rosin.
