Multilayer Technique: the addition of a plastic film was the first step to make brick containers impermeable to liquids and heat-sealable. While in the sixties, an aluminum foil started to be added on the cardboard container to ensure greater protection and extend the shelf life of the packaged solution. The https://liquidsoappackaging.blogspot.com/2025/05/sustainable-packaging-for-oil-and-more.html