One of the most striking symbols of the papal conclave is their method of communicating to the outside world the result of successive ballots. Prior to the cardinals’ arrival, a kind of stove is set up in the Sistine Chapel and a long stovepipe is run all the way up through the roof, supported by a temporary scaffolding, connecting to a chimney that is installed on the chapel’s roof, again, especially for the proceedings of the conclave. The Sistine Chapel and its chimney are clearly visible from St. Peter’s Square, thousands wait to hear that a new pope has been elected.
When each ballot is counted, the papers are bound together and burned in the stove. If the ballot failed to produce agreement, a chemical compound is added to produce black smoke, or “fumata nera,” which lets onlookers know that another vote has been taken but that no pope has been elected. Traditionally wet straw was used to produce the black smoke, but several grey-smoke false alarms over the last century have prompted the move to a chemical agent to ensure the smoke is black.
When a successful ballot is made, it also is burned in the stove, but without any chemical additive the smoke is white, and this “fumata blanca” is the first message to the waiting faithful that the Cardinals have reached an agreement and a new pope has been elected. Pope John Paul II requested that the bells of St. Peter’s Basilica be rung in addition to the white smoke, to make the message unambiguous. This was done upon the election of Pope Benedict XVI, and will presumably be done again at the close of the upcoming conclave.