Callistemon
to both your last posts!
I too have a special pan for boiling eggs, as did my Mum. In fact I think I may be using the one I inherited from her as don't remember ever buying one!. We live in a hard-water area now, as we did when young. I presumed it was some of the calcium from the eggshells that leached out and is deposited on the side of the pan. Have tried suggesting to both sons that they also use a separate pan but they can't be persuaded!
What did you you think you would have by your current age that you don't?
It's official: Grandparents are good for children


. My Mum used whichever pan seemed the right size for the number of eggs, I do the same.