Multilayer method: the addition of the plastic film was the first step to make brick containers impermeable to liquids and heat-sealable. During the sixties, an aluminum foil began to be included to the cardboard container to make sure far better protection and extend the shelf life of the packaged merchandise. https://topcartons.family.blog/2024/12/05/gable-top-cartons-the-future-of-sustainable-packaging/