There is a product we refer to as "death in a can".
I don't usually recommend it for anything but the most dire situations.
When it says only use outdoors or under an outside hood, with gloves and a
face shield, it means it. It is for commercial kitchens and it gives nasty a
whole new meaning.

It removes almost anything, including removing the top layer of aluminum.
It cleaned the carbon off my oversized burner liners in one try -when all
the other oven cleaners and learned chemical/mechanical attempts didn't even
touch it.

E-mail me to remind me, and I will give you the name on the can. (I keep
it in the haz-mat locker (really) and will check it tomorrow.) You can
contact a restaurant supply house to get a can.

It will work, and it does not damage glass.

"Corningware" > wrote in message
oups.com...
> My friend accidentally left a Corningware casserole dish(white) in the
> oven at 400 degrees for six hours.
>
> She was roasting vegetables and garlic in olive oil. Needless to say
> the dish is a mess with burnt on stains that cannot be removed by
> scrubbing etc. It was completely black after charred remains of the
> vegetables were scraped off.
>
> I have tried many things but alas this sentimental dish seems to be
> dead. The black and brown stains seem to be painted on.
>
> I can send you a pic. It's pretty ugly.
>
> Can you help?
>
> Thanks
>
> Cw5k
>