I have a roll of Wilton parchment paper that says it's safe up to 400 degrees. Does anyone know what happens to the parchment if it's heated higher than that? Does it transfer unsafe chemicals to the food? The reason I ask is because I saw an episode of America's Test Kitchen where they use a parchment sling to lower no-knead bread into a Le Creuset pot that's been preheated to 500 degrees and I wondered how they could bake parchment at 500 degrees for 40 minutes without having it burn. Are there brands of parchment that have a higher heat rating?
FWIW, Silpat is rated to 480 degrees and can't be placed directly on the floor of the oven or on a pizza stone.