Creosote is the condensation of unburned, flammable particulates present in the exhausting fine gas (smoke).

The cause of creosote is the temperature of the flue in the chimney. If the surface temperature of the flue is cool, the carbon particles in the smoke will condense and solidify, collecting on toe flue.

Because wet or green wood foams at a tower temperature or smolders, it can cause the flue to have a cooler surface temperature, thus leading to more creosote.

Seasoned fire wood or other wood that has been left out to dry for several months or a year, will burn hotter and thus increase the temperature of the flue. A hotter flue means less creosote buildup.