New pope, from 7 May eyes on the Sistine chimney: this is what determines the white smoke

The chimney on the roof of the Sistine Chapel has been mounted. At this point everything is ready on Wednesday 7 May, when in the afternoon, after the morning "Missa pro eligendo pontifice", the Conclave for the election of the new Pope, after the death of Francis, will open. From that moment on, the eyes of the whole world will be on that very chimney, with the colour of the smoke, black or white, to announce if and when the cardinals will have chosen the new Pope.

At 4.30 p.m. the doors of the Sistine Chapel will be opened with the 'extra omnes', the 'outside all'. In these hours tourists continue to visit the Vatican Museums but not the Sistine Chapel, which has been closed to the public since Sunday. Workers are in fact setting up the spaces and audio, and fixing the floor.

The chimney will be connected to two stoves, one cast iron and one more modern. The first is from 1939 and will be used to burn ballot papers; the second is more recent, from 2005, and will be used instead to burn the smoke that should give the colour black in the event of non-election and white when choosing the successor to Pope Francis. Potassium perchlorate, anthracene and sulphur are used to colour the black smoke; potassium chlorate, lactose and rosin are used for the expected white smoke.

The history of the smokes in the different Conclaves is full of anecdotes because in the past the colour was not always evident, at least at the beginning of the smoke. It was thus decided, since the election of Ratzinger in 2005, to accompany the white smoke with the distant ringing of bells. In this way the message coming from the Sistine Chapel, that there is a new Pope, will be unequivocal. The Sistine chimney, as has always been the case, will have a Vatican media camera pointed a few metres away and should also be equipped with lights, to make any evening smoke evident.

Voting will start as early as the evening of 7 May (but it will be decided on the spot by the cardinals in a ballot). Then from 8 May there will be four votes, two in the morning and two in the afternoon. There will only be smoking at the end of the session, so twice a day.