When the conclave for the election of the Roman Pontiff begins, the cardinal electors will be locked up, under lock and key (cum clavis), until the fumata bianca announces to the world that there is already a Pope. This has not always been the case.

The first record of a pontifical election held with the cardinals under lock and key dates back to 1272. After the death of Clement IV and after almost three years of long discussions without agreement, the cardinals were urged to hasten the election by the citizens of Viterbo, where they were gathered. To this end, they confined them under lock and key and rationed their food, later providing them with only bread and water. To press them further, they raised the roof of the bishop's palace in order to expose them also to the inclement weather. Even so, it was impossible to agreement, so the fifteen cardinal electors delegated six, who finally chose Theobald Visconti, archdeacon of Liege, who at the time was in St. John of Acre and who after his consecration took the name of Gregory X (1272-1276).

Having learned from his own experience, he decided to regulate the form of pontifical election, for which he took advantage of the convocation of the Second Council of Lyon in 1274. By the constitution Ubi periculum maius the conclave was officially established: it would begin ten days after the death of the Pope, it would be held in strict enclosure in the same place where he had died, the cardinals would live in common, they would be practically prevented from having staff at their service (except in case of illness) and their food would be progressively withdrawn until the election: from the third day, only one meal and, from the eighth, bread and water.

With minimal variations, conclaves have been held over the last nine centuries. Most of them took place in Rome, although some were convened in other places, especially during the age of average, with the French city of Avignon standing out. However, in more recent history only the conclave that elected Pius VII (1800) can be mentioned, which was held in Venice because Rome was occupied by Napoleonic troops. In Rome, not all the conclaves have been held in the Vatican either, although the Sistine Chapel is inextricably linked to the papal elections. The last one held outside the Sistine Chapel was that of Gregory XVI (1831-1846), held in the Quirinal Palace.

As far as the duration of the conclave is concerned, in the age average there are those that lasted for months and even years. Not only the one that forced the regulation in the time of Gregory X, but others like the one that took the monk Celestine V to Peter's Chair in 1294, which lasted two years and three months. More recently, the one that elected Benedict XIV (1740) lasted almost half a year and the one that elected Pius VII lasted three and a half months. On the contrary, the last conclaves have result generally been quite brief, requiring few votes.

In the modern centuries the conclave has been regulated on several occasions. In 1621, Gregory XV established the possibility of a triple procedure of pontifical designation: by acclamation, by compromisers and - the most usual - by secret ballot. Pius X in 1904 abolished the right of veto that some Catholic monarchs (Spain, France, Austro-Hungarian Empire) had enjoyed. The reason was that during the conclave in which this pontiff was elected, the Cardinal of Krakow, Ian Puzynia, on behalf of Emperor Franz Joseph I of Austria, interposed the veto to Cardinal Rampolla (secretary of state of Leo XIII), the great favorite and who would have obtained an important issue of support in the first three ballots.

Much more recently, Paul VI established in 1970 that cardinals lose their right to vote when they reach the age of eighty and, in 1975, that the number of electors issue could not exceed one hundred and twenty. For his part, John Paul II, by means of the apostolic constitution Universi Dominici Gregis, of 1996, regulated everything related to the conclave, introducing a new B novelty such as the change of the residency program of the purpurates. Probably as a result of the two conclaves held in 1978, both Wojtyła himself and the rest of the cardinals could experience the discomfort of residing in temporary rooms inside the apostolic palaces, armed even in the same corridors and lacking any subject not only of comforts but even of the minimum hygienic services. For this reason, he established that the residency program of the cardinal electors during the conclave would be the new residency program of Santa Marta, built specifically inside the Vatican and relatively close to the Sistine Chapel.

Finally, the most recent reform of the electoral system for the election of the new Pontiff has been the one ordered by Benedict XVI in order to ensure in all cases a two-thirds vote for the elected Pope. At purpose it may be curious to recall the case of Pius IX (1846-1878), who in the conclave in which he was elected had the task of reading aloud the ballots. When Cardinal Mastai-Ferreti began to notice that his name appeared recurrently, he asked to be replaced by another, but his request was not accepted, so he was forced to continue reading the rest of the ballots until he verified that he exceeded the required percentage, thus certifying his own election.