Polyethylene Coating: A skinny layer of polyethylene on either side provides sturdiness. The outer layer shields the design and printing, when the internal layer acts like a sealant, generating the carton completely leakproof. The main patents for food stuff paperboard containers day again to the beginning of the final century. https://lite.evernote.com/note/dd507a72-9ea8-57b5-f7cb-bca1536cf783