Centuries-old smoke ritual signals pope’s election

The world is holding its breath as the conclave begins on 7 May 2025, following the passing of Pope Francis on 21 April, marking the end of his 12-year papacy. The Vatican is preparing for a centuries-old tradition that signals the election of a new pope. Announced not by social media or press releases, the vote is revealed by smoke from a chimney atop the Sistine Chapel.

Professor Candida Moss, a theology professor at the University of Birmingham, told the BBC that the smoke in the air allows people “to feel included – as if they are incorporated into this mysterious and secretive affair”.

Black smoke signals that no decision has been made, while white smoke means Habemus Papam – we have a pope. This ritual is watched by millions and transforms the Eternal City into a stage of high suspense. 

During the conclave, two temporary stoves are set up inside the Sistine Chapel. One is used to burn ballots and the other to produce smoke signals by burning chemicals along with the ballots.  The stoves are linked to a narrow chimney that channels the smoke through the chapel roof to the outside. On 2 May 2025, firefighters were seen on the roof securing the chimney cap, while workers were building the stoves inside the chapel.

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This practice of burning the cardinals’ paper ballots dates to the 15^th century, intertwining elements of secrecy and spectacle. This tradition promotes transparency and guards against interference, especially in the past, when electing a pope was a frequent cause of public unrest and anger. 

The chemical compositions behind this religious ceremony were revealed in 2013 when the black smoke was created by burning potassium perchlorate, anthracene (a component of coal tar), and sulphur. In contrast, the white smoke was generated by using a mixture of potassium chlorate, lactose, and chloroform resin. These chemicals are usually burned in the secondary stove to produce distinct smoke colours.

In the past, cardinals were using cartridges with specific chemicals to produce the smoke. According to The Times, during the 1958 conclave, black smoke was meant to be created by burning damp straw with the ballots, but it didn’t catch fire properly. This led to confusion as the initial smoke appeared white.

However, installing a chimney in the Sistine Chapel is an achievement. It is a detailed procedure because the Sistine Chapel was built more than 500 years ago, and it was not designed to deliver smoke signals. Securing the flue could be a difficult process with professionals using an existing opening or making a temporary one to insert it. Made of iron or steel, the pipe extends from the stoves to the exterior and extends through the roof above St. Peter’s Square.

“This is such a precise process because if one thing goes wrong, it’s not just a technical failure – it becomes an international incident,” Kevin Farlam, a structural engineer who has worked on heritage properties, told the BBC.

Over time, there have been proposals to modernize the process – using colourful lights or digital notifications. However, for the Vatican, this ritual serves not only as a means of communication but also as a connection to an old tradition.