METHOD OF APPLYING PHASE TRANSITION MATERIALS TO SEMI-POROUS, FLEXIBLE SUBSTRATES USED TO CONTROL GAS PERMEABILITY

A method of applying a phase transition substance to impart reduced ignition propensity to a smoking article comprising a tobacco column and a wrapper surrounding the tobacco column and having a porous structure with a base permeability. The method comprises forming a pattern of phase transition material on a surface of the wrapper such that, when the phase transition material is subjected to the heat of a burning fire cone of the tobacco column, the phase transition material at least partially fills the wrapper porous structure in the vicinity of the burning fire cone forming an area on the wrapper having a reduced permeability that is lower than the wrapper base permeability. The reduced permeability of the wrapper in the vicinity of the burning firecone imparts reduced ignition propensity such that there is insufficient air flow to sustain combustion.