Two days ago, I dropped the bomb on a 4 qt. Ruffoni copper stockpot to go with my soon-to-be-installed Wolf rangetop. Tonight, I cut off the tags and fired 'er up with a chicken stock. I left the stove to put the little people to bed, returned to a boiling pot, which had the lid sort of 3/4 on, 1/4 off (is that bad technique??) and found the edge of the lid where the steam was escaping was discolored. It almost looks like the copper has been worn off.
Have attached photos.
Is this normal? I'm sick about this.