Abstract: A method for forming a liner in a closure for a container includes forming a plastic closure cap having a circular top wall portion and a depending annular skirt portion depending from the top wall portion, and depositing a quantity of moldable liner forming plastic material in the cap. A liner forming assembly which has a liner tip and a liner sleeve, the liner tip being axially movable relative to said liner sleeve, and the liner sleeve defining a plurality of circumferentially located, radially oriented venting channels positioned on an outer surface thereof, is advanced into the cap to engage the sleeve with the cap, adjacent to the venting channels, to define a liner space. The liner tip is advanced into the cap, relative to the liner sleeve, to compress a liner forming material to form the liner while restraining the flow of moldable plastic between the sleeve and the cap, and while venting gas out of the liner space through the venting channels.