I hope this is the right place to ask this . . .

Today I brewed up some of my 6 day old, home roasted coffee. I brewed it into my hario decanter and then poured it into my mug to let it cool. A few minutes later I noticed a constant creaking/groaning noise. I had heard this several times in the past and I finally figured out it was coming from my cup of coffee! I saw no bubbles of any kind, but I would be guessing some kind of gas is being released? Anyone know whats going on?

Perhaps the mug is heating/cooling and expanding/contracting?

It's quite possible that some of the beans were still alive when you ground them.

Your coffee is haunted. Seek the services of a qualified exorcist.

aecletec wrote:Perhaps the mug is heating/cooling and expanding/contracting?

This is the only explanation I can think of.

Otherwise, "if there's something strange, in your neighborhood..."
Https://m.youtube.com/watch?v=m9We2XsVZfc

If the bottom of the cup is damp, it can create a seal on the counter surface. As the trapped air expands or contracts due to temp change can cause this. I have a mug that did this on a glass surface.

I think I'm going to go with the exorcist. Thanks everyone.