In reply to Removed Userscotsmac:
Hot water heats up air, that raises air pressure and lid pops.
Put a bit of hot water in, put lid on & shake it to heat up the air and the inner surfaces.
Pour out the hot water, watch out for pressure build up spitting out hot water. Fill as normal.
The hot inner surfaces warm the air so you are not sealing in cold air that then heats up so pressure increase reduced.
Although the research team at Nollidge College may have better solution.
Post edited at 19:50