2. Thermal Cleaning - Thermal cleaning is pretty much exactly what you’d expect; the block is loaded into a large oven and baked at a temperature of about 500 degrees. The heat burns off all of the oil, grease, carbon, old paint, and other residue that simple washing won’t remove. Think of it like the self-cleaning cycle on your home oven. Once it’s done here, we’ll be back to clean cast iron.