Here is How the Candle Cap works:

Candle caps , also known as Candle Cappers or Jar Toppers are a unique yet functional addition for favorite "jar" candles. Hate the black soot on your candle but love burning candles?
This unique metal candle cap product makes jar candles smokeless and burn cleaner. Your jar candle will have less soot build up and your candle will have a more finished look with a Jar Topper.