If you soaked the loaf of bread in Sodium silicate and compressed the loaf with a 10- 20 ton press prior to placing it in the chamber, then fired it in an Argon environment, you would have silicon carbide.....a kiln shelf.
There is a great article Feb 2005 Science daily about making petrified wood using similar technique. They placed wood in acid to breakdown the cellulose a bit, then soaked it in hot sodium silicate. It went into an Argon oven and came out petrified. So you could make a kiln out of wood if you wanted to..