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When to replace your microwave and what the real risks at home are
If your microwave is taking longer and longer to heat food, it might have reached the end of its lifespan. An expert explains what can damage it, why sparks fly when metal is inside, and how much protection the door actually provides.
The magnetron can be damaged if the appliance runs empty or contains metal
A microwave does not have a fixed expiry date: a sign that it is time to replace it may be that it takes much longer to heat the same thing. That change can also indicate that the magnetron, the part that generates the microwaves, is reaching the end of its useful life.
Alberto Ruiz Rodríguez, responsible for the plasma and microwave systems line at the Unidad de Sistemas Avanzados de Fabricación de Eurecat, explains how the appliance works and which habits can damage it.
The magnetron should not operate empty
The magnetron transforms electricity into microwaves. To avoid damage, there must be something inside the appliance to absorb that energy: water or food, for example. If it operates empty, the energy can return to the magnetron and damage it.
Sparks can also appear when metal objects are introduced. According to Ruiz Rodríguez, the energy causes electrons to jump from some of the metal’s bonds; that jump is what we see as a spark. This phenomenon can damage the appliance.
Food heats up and transfers heat to the container
Microwaves mainly heat the water molecules in food. Their movement generates heat, which is then transferred to the rest of the food; other components can also be heated.
That is why it matters whether a plastic container is microwave-safe. Some cannot withstand the high temperatures reached by hot food. Others may contain components that absorb microwaves, heat up more, and degrade.
The door is designed to contain the waves
The expert states that microwaves remain inside an isolated metal cavity. The door incorporates metal locks and mechanisms that prevent the appliance from emitting waves if it is not properly closed.
In the event of a leak, microwaves could heat liquids: the water present in body tissues, which the expert estimates at around 70 to 80%, could also be heated. Ruiz Rodríguez notes that it is very unlikely to happen unless the appliance is deliberately tampered with.
Mobile phones and wifi also operate in the microwave range, although the power of a phone is tiny compared to that of a kitchen microwave: the expert puts the latter between 1 and 1.5 kilowatts, and mobile phones in the microwatt range. According to his comparison, a phone’s power is almost a million times lower, insufficient to heat anything.
Microwaves can last for many years, especially older models. There is no specific age for replacing them: if they take much longer to heat than before, it may be time to change the appliance.