In Indian kitchens, there has always been a defacto rule that you should never put metal in microwaves. I have always been told that. I never really questioned it till a few years back when I bought one personally. Let’s debunk this.
First, understand how a microwave oven works. Microwaves are electromagnetic waves, similar to light but with a different wavelength. Home ovens typically use a frequency of 2.45GHz (wavelength = 12.25cm), which falls in the free spectrum of usage (like Bluetooth). This microwave is generated by a unit called a magnetron, usually located behind the control panel in the oven. The generated microwaves form a standing wave in the oven’s cavity. A standing wave means the wave appears stationary, with its crests and troughs of the sine wave fixed in 3D space. These waves interact with water molecules in food, rotating them back and forth to generate heat via “friction” and heat up your food.
So, what happens when you put metal in the microwave? Metals reflect nearly 100% of electromagnetic waves, but they also interact with free electrons on the metal’s surface as it can’t penetrate it. If the metal object has sharp, thin edges, electrons can align and build up a large charge at these tips. When this charge exceeds a threshold, it creates a spark. If the metal is very thin, like aluminum foil, this spark can raise the temperature and cause it to catch fire if there is a flammable object like parchment paper.
That’s why you shouldn’t put thin, sharp metallic objects in the microwave. However, if the metal doesn’t have those features, it’s usually fine. Heck, the internal cavity of a microwave is fully made of metal. My rule of thumb is to avoid metal in microwaves whenever possible. If you must use it, ensure there are no sharp edges. But remember metal does get very hot inside the microwave. Please be mindful of that.
BTW it’s perfectly safe to cook food in a microwave, there are absolutely no negative effects on food because it’s cooked in a microwave. Don’t believe those myths.
