When you put 3 cookie sheets in an oven why the bottom sheet burn?

* Hot air circulation: Ovens rely on fans or convection currents to circulate hot air. When you overcrowd the oven with multiple cookie sheets, the air flow is disrupted. This can lead to hot spots where the bottom sheet receives more direct heat.

* Blocking heat: The cookie sheets themselves can block the heat flow. If they're too close together, the bottom sheet may be shielded from the heating element while the top sheets receive more direct heat.

* Radiated heat: Ovens also use radiant heat from the bottom element. When the bottom sheet is too close to the element, it absorbs more heat and can burn.

Tips to prevent burning:

* Space them out: Leave at least 1-2 inches between each cookie sheet. This allows for better air circulation.

* Rotate: Rotate the cookie sheets halfway through baking. This ensures all sheets receive even heat.

* Use a baking stone: A baking stone can help distribute heat more evenly throughout the oven.

* Preheating: Always preheat your oven to the correct temperature before putting in the cookie sheets.

* Lower the rack: If possible, lower the rack position to give the bottom sheet some distance from the heating element.

By following these tips, you can prevent your bottom cookie sheet from burning and enjoy evenly baked cookies!