Thanks all, I can't put anything on the bottom of my oven as there is a covered element there that you are not supposed to put things on or it effects the way the oven cooks.  I do tend to put things in trays etc.  I recommend no one use the oven power check out what its done to my oven rack.  Chemical reaction by the looks stuffed them 😞 Annoyed as its a fairly new oven.