The user's Staub ceramic dish cracked in a 220°C oven, despite being rated oven-safe up to 300°C. The manufacturer cited two reasons for the failure: placing it directly into a preheated oven and insufficient food coverage on the base. This contradicts the user's experience with a new Pyrex glass dish, which is recommended for use only in a preheated oven. The user seeks a scientific explanation for this apparent difference in heat resistance between ceramic and glass dishes. They are also curious if their Pyrex dish requires food to cover the entire base, as they often bake fish with minimal seasoning. The core of the confusion lies in the contradictory advice regarding preheating and the thermal shock properties of different ovenware materials. Understanding the science behind heat distribution and material expansion is key to resolving this. The user wants to know why glass can withstand direct entry into a hot oven while ceramic cannot. They also question the necessity of food completely covering the base for Pyrex dishes. Ultimately, they desire clarity on safe and effective use of both types of bakeware.