One Should Use Microwave Safe Containers fact

Do You Need Microwave-Safe Containers for Microwave Ovens?

One should use microwave-safe containers in a microwave. Safe containers let radiation pass through them so only the food, not the container, is heated.

With that said, determining whether containers are microwave-safe can be difficult. You can look for the microwave-safe symbol with its three wavy lines showing radiation, or look for the words “microwave safe” on dishes and cups, but these symbols will not tell you if those containers let radiation pass through them, especially after the containers age.^[1]

There is no standardized definition of the term “microwave safe.” A common misperception is that tableware and plastics that are designated as safe will not leach toxic substances into food or become hot enough to burn you. This is not necessarily true.^[2]

TIP: If it doesn’t specifically say microwave-safe, then don’t put it in the microwave. It’s the golden rule, along with don’t put metal in there.

How Do You Tell if a Container is Microwave-Safe?

One reliable way to tell if a container is suitable for a microwave oven is to place it in a microwave with a cup of water in a container you know to be microwave-safe. Microwave at full power for one minute. Use a thermometer of your hand to carefully check the temperature of both the container and the water. The water should be warm, but the container that you are testing should remain cool. You can continue the test for another minute if you are unsure of the result.

Fact: If the tableware or plastic container that you are testing becomes hot, then the radiation is being absorbed by it and is not passing directly into the food you are trying to heat. You can see this demonstrated by VentunoKitchenTips here.

Why is it Important to use Microwave-Safe Containers?

Containers that are not safe for the microwave can leach toxic substances into your food. This is a major concern with plastic containers, although plastic containers are tested by the FDA before they are permitted to be sold and tableware is tested for heavy metals. However, even this safeguard will not protect you from toxins in old, scratched containers. In addition, scientists such as Frederic vom Sall, an expert in the chemical Bisphenol, maintains that there is no such thing as a microwave-safe plastic and that all plastics degrade with all heat and release toxins.^[3] Old, worn tableware, or tableware manufactured without sufficient safeguards, may be labeled as being microwave-safe, when it is not. You need to consider which risk factors you will tolerate.

What other Dangers Should I watch out for with Microwaves?

Unsafe containers could heat unevenly, causing them to shatter. If they are plastic, they may bubble or melt. They will also absorb radiation, not allowing it all to pass through to the food, and cook food unevenly.  A safe container of water or an egg can be dangerous if it is heated too long. Water can explode when superheated, whether it is the water inside a tightly covered egg or water is an open cup. That is why directions for microwaving foods urge you to let it rest for a few minutes after cooking. The radiation takes some time to cease acting.

Even a safe container of water or an egg can be dangerous if is heated too long. Water can explode when superheated, whether it is the water inside a tightly covered egg or water is an open cup.  When boiling water, you may create a situation in which bubbles are not allowed to form. Instead, a part of the water may become hot enough to form a gas, and the gas may explode. This is why it is best to put a wooden stirring stick in your cup instead of a metal teaspoon. The wood fibers provide nucleation sites which will help diffuse explosions.

Metals, such as gold or silver decorative rims on tableware, a piece of foil left stuck to a plastic container or a spoon left in a dish, may cause electrical arcs and destroy your microwave oven.

Fun Fact: Dry things do not absorb microwave radiation while wet things do. That is why directions for microwaving foods urge you to let the food rest for a few minutes after cooking and allow the radiation to stop acting and temperatures to equalize. Hot, wet food heats the air, and this heats the cooler, dryer parts of the food.

1. “Which Plastics Are Safe To Put in the Microwave?” Livescience.com
2. “GHRI Investigates Microwave-Safe Mugs” Goodhousekeeping.com
3. “Microwave safe plastic- is it really safe?” Environmentalhealth.ca