The Science of Holy Smoke: Conclave Messaging Secrets Revealed!


This morning, a friend of mine who lives in Rome posted the following observation on Facebook:

Looking up at the chimney on the Sistine Chapel this morning, I began to see the problem with creating recognisably black smoke in weather like this. With the light grey of the overcast, any solid, including smoke particles, are going to show up appearing very dark in silhouette. It was obvious last night that the smoke was v. black, but in daylight, I think all the smoke they make is going to look dark grey.

But lighting questions aside, the larger question remains: how do they make the colored smoke? A longstanding mystery, yesterday the Vatican Press Office revealed the secret recipe. Henry Fountain, science writer for the New York Times explains:

The white smoke, used to announce the election of a new pope, combines potassium chlorate, milk sugar (which serves as an easily ignitable fuel) and pine rosin, Vatican officials said in a statement. The black smoke, which was used Tuesday evening to signal that no one in the first round of balloting received the necessary two-thirds vote of the 115 cardinals, uses potassium perchlorate and anthracene (a component of coal tar), with sulfur as the fuel. Potassium chlorate and perchlorate are related compounds, but perchlorate is preferred in some formulations because it is more stable and safer.

The chemicals are electrically ignited in a special stove first used for the conclave of 2005, the statement said. The stove sits in the Sistine Chapel next to an older stove in which the ballots are burned; the colored smoke and the smoke from the ballots mix and travel up a long copper flue to the chapel roof, where the smoke is visible from St. Peter’s Square.

There you have it, folks. Considering the rather formidable list of Catholic scientists throughout the ages, it comes as no surprise that even the papal conclave messaging service is just another example of better living through chemistry!

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