a sealed container or air tight clingfilm
the air in the container expands
The hermetic refers to being air tight. The term commonly used is hermetically sealed. An example of a hermetic container would we a glass jar, or any container with an air tight seal.
Then your container was not airtight.
That just refers to a seal that is gas (air, specifically) tight.
An air tight container to keep it from going stale.
in a non see through air tight container
It is moisture and air that causes metal to rust, therefore if something is air tight and doesn't get much air it can't easily rust.
No. Just put in an air tight container.
a couple days in an air tight container
That just refers to a seal that is gas (air, specifically) tight.
2 days in an air tight container