White smoke signaling the election of a new pope is produced by burning the ballots along with a specific chemical mixture designed to create a thick, white plume. The key ingredients are potassium chlorate (a strong oxidizer), lactose (milk sugar as fuel), and pine rosin (a resin from pine trees). When burned, this combination undergoes a vigorous but controlled combustion that produces mostly water vapor and carbon dioxide, along with fine droplets and light-colored ash from the pine rosin. These microscopic droplets and resin particles scatter light, creating the distinctive white smoke. This mixture burns cleanly and produces a dense white cloud that contrasts sharply with the black smoke used when no pope has been elected

. Historically, white smoke was once created by burning ballots with wet straw, but this method was unreliable. Modern chemistry has refined the process to ensure the smoke is unmistakably white. The pine rosin contributes to the white hue by releasing water vapor and oxygen-containing hydrocarbons during combustion, forming a dense fog of water droplets

. In summary, white smoke is made by burning the ballots with potassium chlorate, lactose, and pine rosin, producing a thick white smoke of water vapor and resin particles that signals a new pope has been chosen.