I was making ghee the other day using a pan I've used many times before. As was normal, as the butter melted, but the characteristic small spitting and popping as the water evaporates didn't start. I boosted the heat from 4.0 to 4.5 out of 10. Still no spitting and popping, but a geyser of butter blew out of the pan onto the stove, the countertop and even several feet away on the floor. I was out of range, so I wasn't burned. Nothing remotely like this has ever happened. Why would it go from no reaction to overreaction?
(Thanks to everyone who helped with my slotted spatula question some weeks back. I now have better ones than those I was seeking to replace.)