In our last video, we mentioned that the oven must be preheated.
Why is this important?
Fragile dishes such as meringues and souffles can be harmed by the strong air current generated by the rising combustion products (hot gases) generated in a gas oven. Airflow in a gas oven will surge as the burners are turned on and off by the thermostat. An electric oven is superior in this respect as the heat is primarily radiated from the heating elements - convection currents are much less since no mixture of water vapor (steam) and hot carbon dioxide is created by the burner. When the oven has reached the desired temperature, the convection air currents are at a minimum and the blackbody heat absorbed by or radiated from the oven walls has stabilized.
Back in the days when stoves were cast iron and wood fueled, precise oven temperatures were almost unknown in the average American home. Bakers built large brick ovens with indirectly heated thick walls and kept the fire going all day to produce the stable heat they needed.
We can also argue that the thermal shock of placing a dish such as a meringue or a cake in a hot oven can harden the surface skin so the air bubbles remain and a light fluffy dish can be created.
Many souffle recipes call for the oven to be preheated to a higher temperature than the cooking temp. This is so the convection currents are at a minimum when the dish is placed in the oven and the burner doesn't turn on for the first few minutes.