Multilayer Process: the addition of the plastic film was the first step to help make brick containers impermeable to liquids and heat-sealable. From the 1960s, an aluminum foil started to be extra to the cardboard container to be sure improved security and lengthen the shelf lifetime of the packaged products. https://sustainablewaterpackaging.blogspot.com/2024/10/gabletop-pak-leading-charge-in.html