In ordinary gas baking oven, it is assumed that lower rack gets higher temperature than upper. The bay which the dial type thermometer resides gets the lowest temp. The heat source is coming from oven lowest portion. Heat naturally travels upward and the farthest object gets the lowest heat.
Baking oven construction and design might contradict this assumption so verification was necessary. It is a 2 racks 4 trays oven, ( 2 trays per rack ). Needed to know which rack gets the hotter temp and if the temp distribution in each rack was even.
So I preheated the oven to the desired temp. Got a bread. Cut out few rectangles. I made sure that brown bread surface was excluded from the cut. Prepared four trays. Placed bread squares on tray middle. Then placed it inside for about 10 minutes.
The breads on upper portion were golden yellow while those on bottom were almost dark brown. It clearly proved that lower rack is getting higher temp. However, it was still good to know that temp distribution in each rack is even.
My baking practice. Place the food on lower rack first. Let it there for the required time period. Open the door. Transfer it to upper track. The lower rack is then free for another set. This way the food I am baking is getting high temperature boost first and then a lower more subtle heat.
Then. I bought an oven thermometer (the one which is meant to be inside oven). Hung it below upper rack so I could get the approximate temperature of the lower. During preheating, the upper thermometer was getting 50 degree F higher. As the baking process progress, the upper and lower rack were exhibiting the same temp reading. I am confused. I sure need more experience on this oven thing.