I meant to mention this when first responded to your post. While making the maple candy it try to boil over on a few occasions, and I did have to lift the pot to stop it. Eventually it stopped trying to do that.
Your example really helps me understand the two types of foam and when I should add the drop of canola oil.
Just out of interest, is there something unique about canola oil, or could one use corn oil or avocado oil?