Metal should not be placed in your microwave. Simple aluminum containers can cause sparks to happen. Ditto with silverware. What more if you put a whole toolbox in your microwave? Or even a magnet? Don’t do that. Don’t put anything metal, steel, aluminum, copper, staple wire, or tin inside.
Your microwave shouldn’t microwave anything metal. So can you microwave stainless steel lunch box? Not really. If you want to know exactly why, keep on reading.
Can You Microwave Stainless Steel Lunch Box?
No. You can’t and you shouldn’t. The healthy container options for reheating your food are thick ceramic or glass dishes, followed by microwave-safe plastic with no cracks or damage on it.
Stainless steel boxes, on the other hand, should not be microwaved because they’re not microwave-safe. This is true for anything metal, including tin foil (aluminum), cobalt balls, screws and nails, a whole smartphone, and stainless steel.
The Nature of Metal Inside the Microwave
Inside the microwave oven, metal functions as a mirror would to light. It reflects and deflects the oven’s microwaves or micro radiowvaes. This creates the arcing phenomenon, sparks, and fire. If you don’t turn off the oven immediately, the oven could malfunction or even explode altogether.
The safe thing to do is use a ceramic dish or even microwave-safe containers with the lids slightly ajar for the best food reheating results.
Further reading: What Happens When You Put Metal in a Microwave?
What is Arcing?
Arcing is when electrical sparks or static happen due to the close proximity of the metal item to the metal walls of the microwave oven. Arcing can also occur in crumbled or edgy metal like aluminum foil since the sparks and electricity happen between these sharp corners.
Metal with kinks or crumpled aluminum presents a bigger risk. Crunched of metal creates areas of concentration. The rowdy electrons will then spark up like it’s the Fourth of July, with them bouncing into the air and making a bonfire.
Superheating is Also a Problem
When putting metal inside your oven, remember that the metal also contains loads of electrons. These can get pulled by the microwaves that cause a thin sheet or portion of the metal to get superheated so quickly that the appliance might burn or explode.
The arcing and superheating phenomenon could hand-in-hand destroy your microwave faster than you can say, “How long is the warranty for our microwave?”
You may also like: What Are The Things You Should Never Put In The Microwave?
Many Convenient Ways to Reheat Food
There are many convenient ways to reheat food aside from microwaving them. There’s also many convenient ways to reheat food in the microwave by varying the types of food containers you use. Remember to use a pot gripper or oven mitt when handling hot containers!
Toaster Oven or Conventional Oven
A great alternative to the microwave is the toaster oven. You can use a metal box in an oven, especially in the office setting. You can use metal for reheating in a regular or toaster oven. It’s less likely for metal to get superheated in an oven that uses conduction heat instead of microwave-induced heat.
Convection ovens significantly speed up baking and roasting compared to regular ovens but not at the level of microwave ovens. On top of conductive heat, convection ovens use convection or hot air circulation to heat up food. This allows you to heat food up at the fraction of the time.
To heat up via stovetop, empty your food from your lunchbox to a frying pan. Put a splash of water to the pan to dampen it. Cover the food with a lid for additional steamy goodness. Your food should end up hot and delicious in 5 minutes.
A slow cooker is what you can depend on for meals, casseroles, and so forth you’re supposed to make ahead. They have a “warm” feature that keeps them warm by the time you decide to eat. Just pop them into the cooker until they’re nice and toasty.
You can use steamer or sous-vide for reheating. Just avoid using plastic pouches to heat via steamer. They tend to leach off bisphenol when steamed, resulting in food contamination. Use a silicone pouch that’s tightly sealed and non-toxic (like Stasher Bag).
Submerge the food in the steamer for gentle steaming. For Chinese meat buns, you can use them as cookers.
Lower your food into the Instant Pot with your metal lunch box. Use a silicone sling with straps. If you’re not rushing to eat your food and you want to warm up your meal slowly, use the Instant Pot’s “Keep Warm” or “Slow Cook” features.
If you wish to rush reheating your food, use the “Steam” function instead. That’s the beauty of the Instant Pot—it’s like a slow cooker and steamer in one device. Regardless, you need water in both instances to get your food warm enough.
Add a cup of water at the bottom of the insert pot. When the food ends up hot enough, you can then lift the lunchbox out of the pot using the sling accessory’s handles.
Why Plastics and Microwaves Don’t Mix
Like in the case of bisphenol contamination when you use plastic pouches, you can also risk plasticizer contamination when you use unsafe plastic containers in the microwave. Many reusable containers, like those made of Tupperware, should be safe with microwaving.
Tupperware and microwave-safe plastic containers tend to be hard, high quality, dense, and hard. They’re also approved by the FDA for microwaving because they don’t leach off BPA unto the food when heated. Glass and ceramic containers are even more BPA-free though.
Another thing to watch out for is to avoid using plastic containers that are damaged. They’re as dangerous for reheating as non-microwave-safe containers because the plastic has been compromised.
Also, Take Note
When it comes to reheating foods stored in containers, microwaves are among the most popular solutions around. They might be a packed lunch or last night’s leftovers. However, not all containers are considered microwave-safe.
Metal in the microwave typically results in sparks and electricity that could lead to fire or superheated metal (hotter than the boiling point of water).
A stainless steel lunchbox or container should never be used in a microwave for reheating. If you want an eco-friendly reheating container, use ceramic, glass (extra thick), or a microwave-safe plastic container (no dents or cracks, please).
- “What happens when you put a steel lunch box in a microwave oven?“, Quora.com, July 19, 2019
- Leanna Smith, “Why No Metal in Microwave?” EcoLunchboxes.com, Retrieved May 19, 2021
- BryAna Stearns, “What Happens When You Put Metal in the Microwave“, Spoon University, Retrieved May 19, 2021