Method of applying phase transition materials to semi-porous, flexible substrates used to control gas permeability

A method of applying a phase transition material to impart reduced ignition propensity to a smoking article, the smoking article comprising a tobacco column and a wrapper surrounding the tobacco column, wherein the wrapper comprises a porous structure with a base permeability, the method comprising forming a pattern of the phase transition material on a surface of the wrapper such that, i) in the absence of heat of a burning firecone, the base permeability of the wrapper is not reduced by more than 20% as a result of the phase transition material, and ii) when the phase transition material is subjected to heat of the burning firecone of the tobacco column, the phase transition material at least partially fills the wrapper porous structure in proximity to the burning firecone to form a non-fixed band on the wrapper having a reduced permeability that is lower than the base permeability;

• and surrounding the tobacco column with the wrapper;
• wherein the reduced permeability is selected to permit sufficient air flow through the wrapper to sustain free burn;
• and further wherein the reduced permeability is also selected to impart reduced ignition propensity when the smoking article is placed on a substrate, such that there is insufficient air flow through the wrapper to sustain combustion of the burning firecone or to sustain an intensity of the burning firecone necessary to ignite the substrate;
• and further wherein the phase transition material is selected from the group consisting of paraffin, tobacco wax, Solanesol, carnauba, Beeswax, microcrystalline wax or combinations thereof.