The earliest ovens date back to the around 29,000 BC and through centuries of cooking with earth, ceramic, masonry, cast iron, and other materials, today we have two main ovens – the microwave and the conventional oven. The conventional oven was invented in the late 19th century while the microwave oven was not invented until the late 1940s by Percy Spencer. Percy discovered the key to how a microwave works while playing with electricity and accidentally melted a chocolate bar. The microwave became popular in the 1970s.
Both ovens can be used for heating but have very different purposes. The microwave saves time and energy because it cooks food immediately. It is most common in convenience cooking while the conventional oven is better for baking and browning.
The microwave cooks with microwave radiation, waves of energy also called radio waves, generated by a magnetron. A magnetron is an electron tube for amplifying microwaves. The radio waves bounce back and forth off the metal walls very fast in an invisible up-and-down pattern of electricity and magnetism that races through the air at the speed of light (300,000 km or 186,000 miles per second). (Woodford)
Waters, fats, and sugars in foods absorb heat in microwaves because microwaves channel heat energy directly in to the molecules. When these waves enter food, they cause the food molecules to move, which creates heat. (Reed, 4) The more the molecules move, the hotter the food gets, but the temperature of the air remains the same.
While microwave ovens cook food everywhere all at once, conventional ovens cook food from the outside to the center. Conventional ovens cook food with hot, dry air, which is why conventional ovens need to be pre-heated before the food is placed in the oven for cooking. A conventional oven is usually between 1000 to 2000 watts, but it does not consume all of that energy to complete cooking a dish. Of course, this also depends on the size of the oven.
The process of cooking food faster also means that food will cool faster; therefore, food cooked in a microwave will cool faster than food cooked in a conventional oven. This process is due to a process called thermalization, which is the process in which food absorbs heat molecules. (Bodine) The microwave radiation used to heat food quickly and conveniently does not allow enough time for the thermalization process to be completed, meaning the food didn’t absorb all the heat. In an oven, the slow heat gives the food plenty of time to fully absorb the heat, and this allows the food to stay warmer longer after it has finished cooking.
Another important factor is the size and shape of what you’re cooking. Unlike conventional ovens, microwaves can’t penetrate more than an inch or so into food, because the waves lose energy from the moment they enter the food. The deeper the wave goes into the food the less energy it has to keep going. This is why conventional ovens are better for baking larger dishes.