Hermetically sealed metal containers

The preservations of canned products require hermetically sealed cans.  Presently three types of hermetically sealed containers are recognized by the food industry:
*Rigid
*Semirigid
*Flexible containers

By the early 1900s, the manufacturing and sealing cans were accomplished by machine. The technique was developed by Peter Durand, who used tin coated iron containers in place of glass jars. He was granted a patent in 1810 for his technique of preserving foods in hermetically sealad tin cans.

Double seam made by five layers compressed 

The lid used for the cans contained a rim to which a plastic casket could be added, and rim to could be sealed tightly by machine by first crimping it over and under the flanged top of the can body and then pressing the two together by a second roller operation.

The plastic gasket made the can airtight by filling the tiny voids produced between the rim of the cover and the flange of the cans as they were brought together.  The process of creating an airtight closure by attaching the can end component to the can body is called double seaming.

This double seem is a metal-to-metal joint formed by mechanically interlocking five layers of metal together three from the can end and two from the can body.
Hermetically sealed metal containers