The election of the pope is a major geopolitical event – the leader of the Catholic Church represents and influences the 1.4 billion Roman Catholics around the world. Its election happens in a conclave, where the electing cardinals are locked in the Sistine Chapel and select the new pope. Since the 1800s, smoke signals have been used to communicate the results of the vote.
The smoke is created by burning the ballots, and originally just meant that no pope had been elected. It was only in the conclave of 1914, which elected Benedict XV, that different smoke colors were used for the first time. There are two now, but there also used to be a secret third one for a while.
It is the white smoke (fumata bianca) that is the most important. The ballots are burned with three substances to make the smoke white. One is potassium chlorate, which is a white solid used in mouthwashes and fireworks. Then there is lactose, the type of sugar that’s found in milk. And finally, there is rosin (also known as colophony), a resin that comes from pine trees and other conifers. Once, the white smoke appears, bells will ring across Christendom and the Protodeacon of the College of Cardinals will go in public and say: “Annuntio vobis gaudium magnum; habemus Papam!”, meaning “I announce to you a great joy, we have a pope!”
But before the joy, we have the black smoke (fumata nera). Any ballot in which no candidates receive more than two-thirds of the votes doesn’t result in the election of a pope. In that case, the ballots are burned with three different chemicals; one is potassium perchlorate, then there is anthracene, and finally, sulfur.
There used to be a yellow smoke, too (fumata gialla). That was to test the stove and the temporary chimney used to burn the ballots. However, since 2005, the traditional stove that has been used since 1939 has been connected to a modern one that burns colorful smoke, so that there can be no doubt as to whether the smoke is white or black – something that had caused confusion in the past.
Source Link: How Is The Black, White, And Secret Third Smoke Made During The Conclave?