Certain materials are safe for microwaving, like ceramic and glassware. Even certain glassware isn’t necessarily microwave-safe because it’s too thin or it gets too hot when you microwave it for even a couple of minutes, leading to breakage of shattering risk once it cools down too quickly. Certain materials should never be used with your microwave oven, like plastic and Styrofoam. When heated, they tend to leach out toxic chemicals.
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Even microwaveable items can only be microwaved for a certain amount of time before they’re no longer microwaveable, like microwavable plastic and Styro. What are Microwave safe materials? Keep on reading to find out.
Which Food Container Materials Are Safe for the Microwave?
The following are perfectly microwave-safe materials with only a few caveats here and there.
- Ceramic and Glassware Dishes: They don’t only house your hot dishes fine without melting. They can also serve as great containers when you microwave leftovers or defrost frozen meats and some such.
- Wax and Parchment Paper: These are also fine when microwaving. They’ve been used for keeping greasy food from exploding all over the insides of your oven since the inception of microwave ovens.
- Napkins, Towels, and Paper Plates: Towels you can microwave just fine. Ditto with napkins but it’s better to not do it because there’s no reason to have hot napkins. In regards to paper plates, as long as they don’t contain a layer of plastic, foil, or wax coating over them. Ceramic plates are simply better than paper, though.
Which Materials Shouldn’t Be Microwaved?
Here are the materials that should give you pause before you go on microwaving them.
- Metal Anything: Metal inside a microwave is a bad time. Metal can get really hot, they cause sparks, and they react rather differently to other microwave-safe materials like ceramic and glass over microwave rays. When you microwave metal, they reflect the microwaves, which could make them escape from the machine or possibly destroy the device.
- Aluminum Foil: Aluminum foil is also metallic and reflective. While they’re perfectly fine on your grill or even a conventional oven they’re not so fine to use with microwave ovens exactly because of the reasons you don’t leave your spoon and fork behind when reheating yesterday’s leftovers and whatnot.
- Cardboard Boxes or Brown Paper Bags: Some cardboard boxes can be microwaved but usually it’s better to err on the side of caution and simply transfer food to your plate or chinaware for safe microwaving. Brown paper bags and most cardboard containers can at best end up turning soft due to the heated grease of your food or at worst end up in flames due to sparks from any metal inside them.
- Cold-Storage Plastic Containers: Cold-storage plastic containers for tubs of yogurt, cottage cheese, and margarine should never end up inside a microwave. They shouldn’t be used for heating up anything since they’re purposely made for cold storage anyway.
- One-Time Use Plastic Containers: For the most part, one-time-use plastic wraps and containers should never be used with a microwave in light of their plasticizers potentially leaching into your food as you heat them up.
- Dishes with Metallic Paint or Trim: The ceramic dishes are safe. The metal in them is not. As previously mentioned, microwaves tend to get reflected and deflected by the metal, which can cause sparks that burn your food or arcing microwave radiation that can bounce out of the machine or destroy the device itself.
- Foam-Insulated Containers: Most if not all cups, bowls, plates, and trays with foam insulation shouldn’t be microwaved at all. The Styrofoam in them is more for insulating hot liquids like coffee and soups. They’re not conducive to reheating and might produce toxic chemicals in case it gets hot enough inside the oven to melt or burn them.
Which Materials May or May Not Be Microwave-Safe?
Some container materials are “either or” when it comes to microwave safeness. This means that unless they have a “microwave-safe” label on them you shouldn’t use them for microwaving. So some are microwavable and some aren’t, in other words.
- Plastic: Many plastic containers contain phthalates and BPA, which are plasticizers and “endocrine disrupters” that act like hormones in your body, which in turn can lead to health problems in the future after ingestion. Microwave-safe plastic contains a label saying it’s “microwave-safe”. Just remember that even microwave-safe plastic should only be used a couple of times before disposal and one-time use plastic containers should definitely not be used for microwaving at all.
Read more: Can You Microwave Plastic?
- Styrofoam: Styrofoam, like plastic, contains potentially toxic and carcinogenic chemicals inside of them but only if they get hot enough to burn or melt right on your food. If it’s a microwave-safe Styro container then you’re usually good to go. Just remember that like with plastic, you should check if the Styro container has a “microwave-safe” label on it. Otherwise, don’t bother microwaving with it.
Further reading: Can You Microwave Styrofoam?
- Cardboard: Some people actually successfully microwaved their pizza while it’s still on the box (just open up the lid) made of cardboard. The problem with this is that it’s harder to tell if the cardboard is microwaveable or not. Some cardboard is so thin that if your food gets hot enough to spill grease, the grease will end up turning it into mulch. Therefore, it’s always better to use ceramic, especially since most cardboard containers don’t bother with the “microwave-safe” labeling system found in Styro and plastic.
Read more:Can You Microwave Cardboard?
Frequently Asked Questions
Here are some FAQs regarding which materials can or cannot be used with your microwave oven.
- How Can You Test if a Material is Microwave Safe? If the list above isn’t helpful enough, you can play it safe and always transfer your food to glassware or ceramic bowls for reheating while never using takeout packages and plastic wrap. Otherwise, you can test if a material is microwavable through the following:
- Microwave-Safe Container and Utensil: Fill a ceramic cup with a cup of water or about 250 ml of it along with the utensil, dish, or material you wish to test.
- Which Utensils? A utensil can be a bowl, dish, container, and so forth made of a material not listed above. Or it could be cardboard, plastic, or Styrofoam that claims to be microwave-safe but you have to be sure it is safe.
- Cook for a Minute: Cook everything at a maximum power of a minute. Feel the utensil afterwards if it’s cold or warm. If the utensil is warm, don’t use it for microwaving. If the utensil is cool then it’s okay for microwaving.
- Warning: Don’t exceed 1 minute of microwaving, because microwave-unsafe material might burn or catch fire if you go further than that.
- What is Arcing? Arcing occurs when the electromagnetic waves from the microwave oven’s magnetron hit something metallic or reflective, be it your silverware or metal foil. They appear in flashes or sparks. It could damage not only your food by setting it on fire but the microwave itself as well.
- Is There a Way to Use Aluminum Foil with a Microwave? Yes, but only for shielding. You need to cut or tear small smooth pieces of it to cover thin parts of poultry or meat. Don’t put the foil close to the oven walls to prevent arcing. It should be about 2.5 cm away from the walls of your microwave oven.
- Any Chinaware or Dinnerware will Suffice, Right? No. Like in the case of microwavable plastic, your microwaveable dinnerware, ceramic dishes, or fine china should not be cracked or chipped. Ditto when it comes to glassware, come to think of it.
- Can Thermometers Be Heated Up with Your Microwave? We recommend you don’t do that since it’s safer to use with a conventional oven like when you’re cooking turkey dinners and whatnot. Otherwise, use a microwave-safe thermometer only.
- How Do You Microwave Glass Jars? When microwaving glass jars, remove the lid every time, especially if it’s metal. Use the jar to only heat up food until it’s warm instead of piping hot. Many glass jars lack sufficient heat resistance and might break if heated up for too long.
- All Glassware is Microwave-Safe, Correct? Incorrect. Only use heat-resistant glass and don’t microwave it too hot like in the case of glass jars. Additionally, make sure it doesn’t have a metallic handle or something. Don’t use chipped or cracked glassware either.
- How About Wood? Is That Microwaveable? While there are cardboard boxes—another tree-based byproduct—that can safely be used to reheat takeout food in your microwave oven, using a wooden bowl might be a no-no. The wood will dry out inside the oven, which will then result in splitting and cracking.
In a Nutshell
There are materials you can microwave over and over and still end up fine, like ceramic plates. There are materials you should absolutely not stick into your microwave, like metal. There are also materials that may or may not be microwaveable so you need to check their labels, like plastic, cardboard, and Styrofoam. Certain plastics can be reused and microwaved but only for a limited time and only if they remain in one piece (no scratches or cracks on them). Ditto with cardboard and Styro, but the most common are plastic containers with the “microwave-safe” label.