I bought a Crown Lynn (New Zealand) casserole at the thrift shop. It was in perfect condition and says "microwave cookware" on the bottom so I figured it was a more recent run. When I started baking bread in it, these brown markings appear, like stardust all over it. I have read other posts on here about cracked ceramics etc. but can't find if this is normal. It is very hard to wash off but seems to mostly if I really try. I guess I am wondering if it's a bad glaze, shouldn't be used to bake at high heat or other problems with it. It's mostly on the lid and I am using newer multi-function electric oven (small) because that's all we have. submitted by /u/Roscia_zen