Fumata BIanca (Robby Boey)

Beginning in the early 19th century, the ballots cast by cardinals during a papal conclave were burned after each round of voting. The resulting smoke became the outward sign of whether a new pope had been elected: dark smoke signaled no decision, while the absence of black smoke indicated success. By 1914, this practice was formalized: black smoke (fumata nera) rising from the temporary chimney atop the Sistine Chapel announced an inconclusive vote, while white smoke (fumata bianca) proclaimed the election of a new pontiff. Ballots from two rounds were sometimes burned together, meaning smoke did not necessarily appear after every vote.

Before 1945, conclave ballots were sealed with wax. When burned, the wax affected the smoke’s appearance: damp straw was added to produce black smoke, while the natural composition of wax, often containing beeswax in the 19th century, could generate whiter smoke. As sealing wax evolved, its ability to create distinct smoke diminished, contributing to confusion in some conclaves.

This uncertainty became particularly noticeable during the 1939 and 1958 conclaves, when the color of the smoke was difficult to interpret. The ambiguity in 1958 even fueled conjectures later known as the “Siri thesis,” based on claims that the initial smoke signaled the election of a different pope.

To ensure clarity, beginning in 1963, chemicals were added to the burning process to make the smoke unmistakably black or white. Since 2005, the ringing of St. Peter’s Basilica’s bells has accompanied the appearance of white smoke to further confirm the successful election of a pope.

The image is an artist's impression of the fumata bianca, based on a stock image.