Do Microwaves Heat From The Inside Out?

My microwave is perhaps the one kitchen appliance I truly couldn’t live without, but until recently I hadn’t given a lot of thought to how they actually work.

I kind of knew that they worked differently to conventional ovens, and that they somehow heated food from the inside out, rather than the other way around.

I decided to have a dig around to find out why microwaves work this way, and I’ve put together an article that explains how this indispensable device actually works its magic!

A slice of pie being served from an aluminum tray

How Microwaves Work: The Basics

Microwave ovens heat up food by using – obviously enough – microwave energy.

This is a form of electromagnetic radiation that “agitates” the water molecules in your food, causing them to move around extremely quickly.

This creates friction, which in turn generates heat. It’s the same principle as warming up your hands by rubbing them together, albeit in a very different way.

Microwave energy penetrates food, however, which means the heating process is focused at the center of the dish.

This heat then radiates out from the center, leading us to the explanation that microwaves do indeed heat from the inside out.

This process actually explains why you need to work with microwaves in a very specific way too:

  • You need a turntable which rotates the food, and ensures energy is directed at it from all possible angles.
  • Very often you’re advised to stir the food halfway through cooking. This helps to circulate the heat, and also create new, cooler centers.
  • If you don’t go to this extra trouble, you’re very likely to find hot and cold spots in your food. That’s because some areas have taken more of the energy, while other areas have been left out!

Frequently Asked Questions

There are a handful of questions that often come up around this topic.

I thought it would be helpful to wrap this article up by answering some of them.

Do conventional ovens cook from the inside out?

Conventional ovens don’t cook from the inside out, because the heat is generated outside of the food and then directed – often by fans – around it.

The heat then slowly penetrates to the interior of whatever you’re cooking. It’s basically the opposite of how a microwave works!

Should microwaves get hot on the inside?

Because of the way that microwaves heat food, they shouldn’t get too hot on the inside.

That said, there will of course be some residual heat created by the food itself once you’ve finished cooking it.

It’s perfectly normal for the outside of the microwave to get quite warm due to the heat created by the electrical components. Depending on where exactly those components are, some of that heat may end up on the inside too.

Unless the inside of the microwave is unbearably hot when you take something out, this isn’t something you should worry about too much.

Where is the hottest place in a microwave?

The hottest place in a microwave tends to be the center of the appliance.

By design, microwave energy is directed towards the middle of the oven, which is where your food is most likely to be.

Why is my food still cold after microwaving?

I can think of a few reasons why your food might still be cold:

* It wasn’t heated for long enough. Microwaves are designed to get the job done quickly, but you still need to give it enough time!

* Your power setting is too low. It’s a balancing act between timing and power, but if you cook something on too low a setting you may notice cold spots, or an overall cold temperature.

* The turntable isn’t turning properly. In order for your food to be heated evenly, your turntable needs to rotate without any restrictions. Check it turns freely, and give it a good clean if anything’s clogged up in there.

* You didn’t stir the food. Not all foods need to be stirred, but this will certainly help move the temperature around and make sure everything’s heated evenly!

* The food started off very cold. If you take food straight from the refrigerator and put it in the microwave, it will need more time to heat than food warmed up from room temperature.

* You misread the instructions! We’ve all done it. If you’re heating pre-prepared food in particular, there’ll often be two or more stages to the heating process. Make sure you use the right power setting for the right amount of time, and follow any instructions you have carefully.