Multilayer method: the addition of a plastic film was step one to help make brick containers impermeable to liquids and heat-sealable. During the 1960s, an aluminum foil began to be included into the cardboard container to make certain much better defense and extend the shelf life of the packaged product https://share.evernote.com/note/02921077-c176-82d8-7d79-e303476ac92a