In dealing with the expanding and contracting metals, in fabrication and casting, most materials when they heat up will go back to normal mass/volume when they cool. So, if you heat up a stem, will it not go back to normal when it cools, and if not, what voodoo physics are involved with that?
I like the stretched stem theory, although I would question whether a stem ever gets that hot, and if so, were you pretending to be a freight train?
I've also heard that when the stem is removed the moisture in the briar causes expansion and contraction. But, then again, why does the stem being removed affect this as opposed to just happening when the stem is in there?
Someone also explained that when separated the briar doesn't shrink back to its normal size. And, that makes no sense to me either.
Sure, there is expansion and contraction at different rates. This makes it easier to remove a stem that was put in the freezer and loose stems will tighten up temporarily when smoked from the heat. I get this. But, once they return to normal temperature, they should also both return to same mass/volume.
Nah, I think I like the stretched stem idea better. I have never had an issue with one of my stems, and I will pop them apart while smoking, after a smoke, before a smoke, whenever the notion hits. And, I have never had a loose stem. Maybe, these big heavy handed guys just yank 'em apart, stretching the stems. Maybe. That works better than any of the suggested ideas that I've heard over the years.