Multilayer procedure: the addition of the plastic film was the first step to help make brick containers impermeable to liquids and heat-sealable. Within the 1960s, an aluminum foil began to be included into the cardboard container to be sure superior security and prolong the shelf lifetime of the packaged product. https://share.evernote.com/note/1e40625b-121b-7870-eb2e-73c5cd5384a6