Brewed my first batch in 15 years this weekend, just as much fun as I remember! I used to brew 5gal and had an immersion wort chiller, so no lid during cold break. Now I brew 1gal batch in a 4gal kettle and immerse the SS kettle (with lid on) in ice water straight from boil. Shortly after dunking the kettle, the lid became very stuck onto the kettle. I could not budge it (I tried a lot of terrible things...) until the kettle presumably reached room temp and I could slip it slightly off and heard the gas hiss as the pressure equalized. My thinking is lidding the pot seals the system and the difference of ice water temps outside and boiling temps inside cause a vacuum (or something similar) inside which sticks the lid. In hindsight probably cooling the lid would help but I don't like that risk of contaminating the wort. Is this pressure bad for the beer? Should this be avoided or is it OK to use this as a nice way to ensure sterility after the boil? Can it damage the pot? I did not see any visible signs of deformation (pot is brand new). Happy to hear comments, thank you!
I'm amazed that you had a metal lid seal itself to the metal rim of the pot. Precision machining would seem to be necessary to achieve that. I'm guessing that there was some sticky steam residue on the rim of the pot that acted like glue to cause your issue. Maybe a wipe with a damp paper towel in the future before placing the lid on the pot would keep this from happening again.
I was rather surprised too. The top of the pot has a flat flange that matches a bottom flange on the lid. I kept the lid off during the entire boil, but it is very likely that the pot top was sticky from steam. I'll try a quick wipe before lidding next time to see what happens. The hissing of steam when I finally slid the lid is what makes me think it was an internal vacuum. IDK, at least I'm sure it kept the wort sanitary!
Your beer was not pressurized, rather under a partial vacuum . . . cooling reduces pressure of most all gases. If there had been pressure in the kettle the lid would have ended up across the room. Normal air pressure acting against the lid over a partial vacuum is what caused the seal. Even at reduced pressure you had the same quantity of air inside (the molecules just became lazy). Pretty sure the levels you're talking about are small, any kettle that can't take the pressure doesn't belong in the kitchen . . .
