Why putting metal in a microwave can be dangerous or just pointless
In short: Most people believe metal is strictly forbidden in the microwave, but the reality is more nuanced. While some metals are specifically designed to be there to help browning, other objects can cause erratic wave deflection, potentially damaging your appliance or creating dangerous electrical sparks.
To understand why metal behaves strangely in a microwave, one must understand the role of electromagnetic radiation. Generated by a device called a magnetron, these waves pulse rapidly inside the oven. While they pass through glass and plastic, they are absorbed by the water content in food, causing molecules to oscillate and generate heat. These waves function similarly to radio waves. They are emitted by a component known as a magnetron.
Metal, however, acts as a reflector. Instead of absorbing the energy, a metal object deflects the waves, sending them jumping erratically around the oven, which can potentially damage the appliance's interior. This makes metal 'counterproductive' if your goal is to heat food efficiently. The oven's internal walls are made of metal to reflect these waves back into the cavity. This ensures the energy remains contained within the appliance.
In certain conditions, metal can also cause sparking—a phenomenon described as being similar to lightning. This occurs when the oscillation of the microwaves produces a concentrated electric field at the edges or corners of a metallic object, ionizing the surrounding air. While some manufacturers cleverly use thin metallic layers in packaging to help food brown, leaving such items in too long can lead to incineration. Sharp edges on metal objects are particularly prone to this effect. This is why cutting food into irregular shapes can increase the likelihood of sparking.
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Sources
- Summary by Intellect · source: Why You Can't Put Metals in the Microwave
- Also: Why can’t we put metal objects in a microwave?
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