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No! Tinfoil ball in microwave won’t make shiny sphere – it could cause fire

A meme shared on Facebook shows a crumpled ball of tinfoil, then a shiny metal sphere.

“If you form tinfoil into a sphere and microwave it for 6 to 7 minutes it will smooth out and be shiny,” it reads.

The meme is both false and dangerous. Crumpled tinfoil in a microwave can cause a fire, as this YouTube video shows.

‘Be extremely vigilant’

The US Department of Agriculture (USDA) says small pieces of tinfoil – also known as aluminium foil – can be used in a microwave to shield portions of food. But the foil must be smooth, not crumpled in any way.

It says you should rather use plastic, ceramic and plastic containers for food cooked in a microwave – as long as the containers are labelled “microwave safe”.

And according to an article on Insider, even if the manual for your microwave says you can use tinfoil in the appliance, “you still have to be extremely vigilant”. 

Thin, wrinkled pieces of foil can’t reflect the electromagnetic waves – microwaves – that the ovens use to heat and cook food, the article says. So the pieces will quickly heat up until they catch fire. 

“You'll probably see sparks,” it says. If this happens, you should quickly turn off your microwave and remove the food and the foil.

But if you don't remove the foil right away, or you microwave metal for an extended period of time – for example, if you were to microwave a ball of foil for three minutes – you'll likely damage your appliance, or even set your kitchen on fire.”

‘Cook microwave’s circuits’

On the Food Science blog, Dave McCowan of the University Of Chicago’s physics department writes about the dangers of putting metal objects, such as tinfoil, in a microwave.

“If there’s nothing but metal in the microwave, you’re left with a lot of mirrors and no absorbers,” he says. So the longer the microwave runs, the waves bouncing around grow like a tidal wave and “eventually get big enough to ‘cook’ the oven’s internal circuits”.

“If the metal you put in the microwave has sharp corners (like crumpled aluminium foil), then the electrons moved around by the microwaves can bunch up along the edges,” McCowan says.

When too much charge builds in one spot, those electrons get very unhappy. And unhappy electrons are liable to – zap! – jump through the air to find a better spot.”

Shiny metal spheres not made in microwave

So where did this dangerous meme come from?

There are claims that you can make a shiny metal sphere out of tinfoil – but not in the microwave.

Buzzfeed says that, according to the original creator of the foil sphere, the process is simple. 

A roll of tinfoil is bunched up into a rough ball. It’s then hammered into the spherical shape. Coarse sandpaper and liquid abrasive are then used to polish the surface to a shine.

A YouTube video shows how it’s done. – Taryn Willows


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