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Can you microwave glass? Plus plastic, foil, paper and more
From glass and plastic to aluminium foil and cardboard takeaway boxes, here’s what you can and can’t safely use as a microwave container
Not all kitchen dishes are suitable for microwave use and some can even be a safety hazard. In fact, the container you choose to microwave your food in can make a real difference to how it turns out.
How you arrange your food, whether you give it a stir while cooking and how long you let it stand before eating can also have an impact.
These tips on microwaveable containers should help make your quickly-cooked dinners as good as they can be.
Looking for a new microwave? Head to our round-up of best microwaves for our top picks.
Can you microwave glass?
Yes, you can microwave glass as long as the container is marked as safe for microwave use.
Glass containers help food to heat evenly and don't leach harmful chemicals. They're also easy to clean and can be used for both reheating and cooking.
Watch out for glass containers with metal accents or decorations, though. These can cause sparks and potentially damage your microwave or even pose a safety hazard.
Glass containers can get pretty hot during microwave cooking due to heat transfer from the warm food, so use oven mitts or pot holders to protect yourself from burns.
Can you microwave plastic?
Yes, in most cases, but as with glass containers, plastic containers must be labelled as microwave-safe.
Even with microwave-safe plastic containers, it's still safest to use them primarily for reheating rather than for prolonged cooking. Continuous exposure to high heat can lead to plastic degradation over time.
It's also best to avoid putting plastic takeout containers, margarine tubs, or other plastics such as yoghurt pots into the microwave, as they're not intended for use in high temperatures.
Can you microwave foil and other metals?
Definitely not. It is never safe to put metal in the microwave, whether it's metal dishes, containers with metal handles or trim, or plates with a decorative metal finish such as a gold rim.
Microwaves use electromagnetic waves to heat the water molecules in food, which is what warms it up. Metals can reflect these waves, leading at best, to uneven cooking, and at worst, to potential damage to your microwave from electrical sparks.
While aluminium foil trays and thin sheet foils are much thinner than metal containers, they're still able to reflect electromagnetic waves, so it’s best not to risk it.
Can you microwave cardboard and paper?
Yes, but only for short bursts. Check that the cardboard or paper doesn't have any metal, glue, ink, dyes, wax coating, or plastic, as these things can cause problems when heated. And don't forget to keep a close eye on your microwave if using cardboard or paper – never leave it unattended.
For longer cooking sessions, it's best to avoid using cardboard or paper altogether. Though it might be tempting to nuke a leftover takeaway in its cardboard box, use a paper plate for easy clean-up or a paper towel as a makeshift microwave lid, it's a potential risk.
Cardboard and paper can easily catch fire or release harmful chemicals when exposed to high heat for long periods of time in a microwave. It's best to transfer your food onto a microwave-safe plate or container before reheating.
When it comes to covering your food, choose microwave-safe lids as these are specifically designed to withstand the heat. They will also help you avoid any nasty food splatters that a flimsy paper towel can’t handle.
If you're after a new microwave, take a look at our latest microwave reviews.
Can you microwave clingfilm?
Yes. Clingfilm and plastic wrap can be used in your microwave, but only if they're the right kind. Look for microwave-safe clingfilm, which is specifically designed to handle the heat without causing issues.
When using clingfilm in the microwave, follow these safety tips:
- Leave a small vent or opening to allow steam to escape. This helps prevent pressure build-up and avoids messy accidents.
- Avoid direct contact between the clingfilm and the surface of the food. Use the clingfilm as a cover over a dish or container, rather than wrapping the food directly in the film.
- If you're unsure about the microwave suitability of your clingfilm, opt for a microwave-safe lid or cover instead.
Can you microwave polystyrene?
No. It's not safe to microwave polystyrene.
When exposed to high temperatures, polystyrene can melt or release harmful chemicals such as styrene, which human and animal studies have linked to cancer. Fatty foods such as meats and cheeses are more susceptible to absorbing these dangerous chemicals.
Although there are microwave-safe polystyrene containers available, we still recommend using safer alternatives such as glass for heating food.
Can you microwave china or ceramic dishes?
Yes, china and ceramic dishes are safe to use in your microwave because they can withstand high heat without any issues. They make become warm during heating or cooking because of heat transfer from the food, but the containers themselves should not themselves absorb microwave energy.
However, even if fine bone china is deemed microwave-safe, it still has a higher risk of breaking or cracking when exposed to sudden temperature changes. Allow the ceramic to cool off before removing it from the microwave to minimise stress on the material and reduce the risk of damage.
When using china or ceramic dishes in the microwave, ensure that they're free from any metallic accents, such as gold or silver trim, as these can cause sparks or uneven heating.
Want more flexibility? One of the best combination microwaves we’ve tested could suit you.
What is the microwave-safe label?
When a container is marked with a microwave-safe label, it means it has been specially designed, tested and proven to handle the heat and energy of a microwave – as long as you follow the manufacturer’s guidelines.
It’s a guarantee that the material won't melt, release funky chemicals, or pose any harmful health hazards to your leftovers.
The microwave-safe label is particularly important when it comes to plastic containers – you can read more about that below.
How to tell if a container is microwavable
If you’re unsure whether a container is microwaveable, perform this simple test.
- Fill a microwave-safe dish with cold water.
- Place it in the microwave alongside the container you want to test.
- Heat the microwave on high power for one minute.
If the test container is cool to the touch while the water in the microwave-safe dish is warm, it means that the container is suitable for microwave use because it’s not absorbing microwave energy.
However, if the test container feels warm or hot, it means that it absorbs the electromagnetic waves and is not microwave-safe.
The bowl of water serves to absorb some of the microwave energy bouncing around the chamber, reducing the risk of potential harm to the appliance by running it empty of food.
Even though a microwave-safe glass or ceramic container will get hot as their content cooks (due to heat transfer from food), an empty one shouldn't absorb heat, so this test will still tell you if dishes made from those materials are safe to use in your microwave.
Rearrange your plate for the best results
You might think that heating food is as easy as popping it in the microwave, hitting the start button, and then pacing around the kitchen until it's done. But there's actually a bit of an art to it.
- Food is more likely to heat quickly and evenly on a plate than in a container. If you've grabbed a container out of the freezer, try transferring the food onto a plate for optimal results. If you can, arrange the food in a thin layer, ideally no deeper than an inch.
- Microwaves tend to cook food around the edge of a plate before reaching the middle. So position thicker items, like large cuts of meat or dense veggies, around the outer edge and thinner foods towards the centre.
- For the same reason, arrange smaller amounts of food around the edge of your plate, leaving a hole in the middle. Everything will cook a lot faster.
- If possible, use a circular container. Microwaves tend to bounce around the corners of square containers, heating some parts of your food more than others, so you end up with ‘hot spots’.
Should you cover food before microwaving it?
Yes, you should. Not only will it save you from the hassle of cleaning up food splatters, but it will enhance the taste of your dish by trapping steam. This helps keep the moisture locked in and prevents your food from drying out. It also speeds up the cooking process, so you can enjoy your meal faster.
If your microwave container doesn't come with a lid, try using a microwave-safe steaming lid or microwave-safe clingfilm.
Go to our survey of top microwave brands to discover which brands our members rate, and the ones to avoid.
