I have read several recent threads that make me want to break out some cast iron frying pans I stored 6 years ago when I bought my glass top range. At that time, I was told not to use the cast iron pan because it might shatter the top. Is that still true? What can I use (non-stick) to give a nice crust on a hamburger or steak? It has become too cold to grill outdoors and George Foreman doesn't do it for me. Thanks!