Multilayer system: the addition of the plastic film was the first step to help make brick containers impermeable to liquids and heat-sealable. In the 1960s, an aluminum foil began to be added for the cardboard container to be sure improved safety and lengthen the shelf life of the packaged products. https://gabletop.business.blog/2024/10/05/embracing-sustainability-with-water-in-gabletop-pak/