Method of hot-filling a plastic container having vertically folding vacuum panels

A method of filling a plastic container comprising:

• (i) Providing a plastic container having:
• a longitudinal axis extending through an opening at a first end of the container to a base at a second end of the container, the first end opposing the second end, the base providing a standing support for the container,
• at least one substantially vertically folding vacuum panel, the vacuum panel being substantially transversely disposed relative to the longitudinal axis, the vacuum panel having a first portion and a second portion, the second portion having a more acute angle of inclination relative to the longitudinal axis and one of said ends of the container than the first portion, wherein the first portion comprises an initiator portion and the second portion comprises a control portion, and
• a sidewall having a plurality of circumferential ribs;
• (ii) Filling the container with a heated or heatable liquid, with the vacuum panel in a filling position;
• (iii) Applying a closure to the container;
• and
• (iv) Applying a longitudinal force to the closed container, so that the vacuum panel flexes and at least partially inverts in a direction substantially parallel with the longitudinal axis, to reduce vacuum pressure within the container prior to opening the container.