Multilayer method: the addition of a plastic film was the first step to generate brick containers impermeable to liquids and warmth-sealable. In the 1960s, an aluminum foil started to be added on the cardboard container to be sure far better protection and increase the shelf life of the packaged product. https://www.tumblr.com/gabletoppak/772202430375116800/gabletop-pak-the-ideal-packaging-solution-for?source=share