Multilayer Method: the addition of the plastic film was the first step to produce brick containers impermeable to liquids and heat-sealable. While in the sixties, an aluminum foil started to be additional for the cardboard container to guarantee much better safety and increase the shelf life of the packaged merchandise. https://share.evernote.com/note/43c0a327-a710-724a-4244-2749efcb3893