Black smoke means no election has been made, while the white smoke is the sign that the Church has a new Pope. For this upcoming conclave, there will be two stoves.
FR. FEDERICO LOMBARDI
"One is to truly burn the ballots and the other to send the some that is seen outside. Because as you can imagine, if the smoke were only from the burning ballots themselves, it would not be enough.”
What is used instead is two chemical mixtures. One is designed to send up white smoke up the chimney, while the other sends it black. But often times, the smoke instead ends up a greyish color.
For past conclaves, before the use of chemical mixtures, the burned ballots alone would produce the black smoke. To have it turn white, the cardinals would use hay.
But with the attention of the world's media zeroed in on the chimney smoke, Vatican officials recognize newer methods are needed to send stronger, clearer signals on the next Pope's elections. During the last conclave, they used bells that rang across St. Peter's Square.