While we were in Iceland, my parents had some friends come to stay at our house. One of them boiled the kettle without putting the whistle-thing down, and it boiled dry and got too hot, the bottom of the kettle is scorched black and the glass of the induction hob is discoloured like there's a layer of something deposited on it and no matter how much I scrub I can't get it clean. 😒 So bloody annoying!