Can metal really be in the microwave?


When opening the instruction manual for the microwave oven, we will see the following note: Do not put metal objects in the microwave oven to heat up. But if you look closely, you will find that the inside wall of the microwave oven, including the oven door, is made of metal, and the lids of some matching utensils are also made of metal! into the microwave? Why can these metals get into the microwave oven?

Why microwave ovens reject metal

The reason metal can't get into the microwave is due to the heating method of the microwave.

The instrument used by microwave ovens to heat food is a high-frequency electromagnetic wave called microwaves. Microwaves are ubiquitous on Earth, and cosmic radiation and electromagnetic signals are microwaves. Fortunately, these widespread microwaves cannot heat objects because they are scattered and unfocused, otherwise humans would not be able to survive safely. Microwaves are collected and sealed in microwave ovens and these microwaves can heat food.

Can metal really be in the microwave?

A microwave uses its internal magnetron to convert electrical energy into microwaves. When microwaves are absorbed by food, the polar molecules in food (molecules with uneven charge distribution, such as water, fat, protein and sugar, etc.) the action of rapid vibration, the molecules collide with each other to produce a lot of heat from friction, so that food heats up quickly. But the effect of microwave heating is useless when it collides with metal.

The metal itself is filled with many electrons that are free to move around. When a microwave falls on a metal, the electrons in the metal vibrate under the influence of the electromagnetic wave and emit electromagnetic waves of the same frequency, indicating that the microwave is finally reflected. Therefore, food served in metal containers cannot be exposed to microwaves. Microwaves, originally used to heat food, will instead heat the dishes, making the dishes too hot and creating a fire hazard.

What is more serious is that if the metal placed in the microwave oven has a large curvature or a pointed fork, such as twisted aluminum foil or a pronged fork, the electromagnetic waves emitted by the metal's electrons will accumulate together, resulting in high voltage and ionizes air molecules into charged particles. Once ionized particles are in the microwave, it will absorb more microwaves because the ability of ionized particles to absorb microwaves is stronger than that of water. Microwaves excite more ionized particles until sparks are produced that can destroy even metallic materials and microwave ovens. Therefore, metal utensils are often not allowed to be used in microwave ovens.

Special metals in the microwave

However, due to the properties of microwaveable metals, some specially designed metals may also work in microwaves.

The body of the microwave oven is made of metal plates. The firebox door is usually glass for the convenience of users, but the inside is also equipped with a metal mesh. Such a metal "cage" can maximize the microwave oven, closed, can effectively prevent microwave leakage from harming the human body. Microwaves entering metal are similar to light entering glass, there is refraction and reflection, so the metal microwave inner wall will reflect the microwaves around, so that the microwaves are concentrated on the food. Using calculations, the scientists designed a suitable hole for the metal mesh on the oven door so that the microwaves are reflected back when they hit the metal and cannot escape.

Metal grills can also be placed in the microwave. This is because a metal barbed wire grill reflects microwaves little and does not protect them as a closed metal dish. Food can also be reheated. on a wire rack. Of course, the metal frame cannot come into contact with the metal wall of the furnace, otherwise an electric spark will also be generated. There are also metal steam cooking utensils specifically designed for microwave ovens. When steaming food, we only want to heat the water at the bottom of the steamer, not the food at the top. Nowadays, using a metal lid to cover the food effectively protects the food from direct heating. The shape of this kind of metal products is often very smooth, the curvature is small, the accumulation discharge phenomenon does not occur easily, and the safety factor is high.

Do you know? It's not that metal can't be used in a microwave, it just has to meet certain conditions, and the role of these metals isn't to heat food. The next time you want to put metal in the microwave, consider what your goal is.