Most of the time when they flow across the whole coin, we call them Linear examples. If it is just a bubble, we call them that. Best way to test on these is to take a toothpick and try to press it down. Note the bubble flow right over the design and field easily.
The first time I really saw the issues with the zinc coins was a few weeks back when I found an 84 p cent but I thought might be a misplaced D because it looked like a d but was really south and close to Abraham's bust. Come to find out, with Robert Lawsons help, that it was zinc rot. Man, I have so many questions, which I think I know might not be errors, but not 100% sure. I guess I can say that, after like a year of wanting to open a profile here, I'm happy I finally did. Everyone's been so helpful and quick to reply.