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How do cardinal electors cast their votes during a papal conclave?

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Cardinals of the Catholic Church, dressed in red, sit at long tables in the Sistine Chapel during the 2005 papal election conclave, surrounded by ornate frescoed walls. — papal conclave Cardinals assembled inside the Sistine Chapel of the Vatican Palace for a conclave to elect a new pope; Vatican City, 2005.

During a papal conclave, cardinal electors cast their votes through a secret ballot conducted within the Sistine Chapel.1

The voting process follows these steps:

Preparation: After all non-electors have departed the chapel, each cardinal writes the name of his chosen candidate on a ballot paper.21
Frequency: One ballot is held on the first day, followed by up to four ballots each subsequent day—two in the morning and two in the afternoon.1
Security: To maintain the integrity of the election, the ballots are recorded and threaded together for security. Once the voting sessions conclude, the papers are burned.1
Threshold: A pope is elected when a candidate receives a two-thirds majority of the votes.31

The outcome is communicated to the public via smoke signals: white smoke indicates a successful election, while black smoke signifies that no candidate has yet reached the required majority.1