You got home late. The food’s cold. There is the take out box, and there’s the microwave, too! Thus, a seeming question comes to mind: Can you simply dump it all in?
Short answer? Sometimes. Not always. The often not written part is where they burn – sometimes literally. Let’s clear up which boxes are OK, which aren’t, and how to warm up leftovers without a mini catastrophe.
Reason you can’t simply take it for granted it is safe
Most of those folded cartons are not 100% paper. Inside they have a very thin lining of plastic or wax to prevent grease and sauce from absorbing right through. The lining is the key part that makes it all the difference. Plain paper will stand up to a quick zap. Plastic or Wax coating? That’s where trouble starts.
Not to mention the hardware. The handle. The little metal wire bail that they swing up on the classic Chinese-food box. Metal. In a microwave. You know how that goes, sparks, perhaps worse.
Thus a box you are holding may contain nothing dangerous, or it may contain something extremely dangerous and you will not be able to tell from the outside. You need to take the time to see for yourself.
The Metal Thing, First
This one’s non-negotiable. Before placing anything in the microwave, look for metal. wire handles will come to mind first, but not last. The corners of some boxes are secured with metal staples. There is a layer of foil beneath the print in some. Boxes with foil lining are standard for food items that need to stay warm and are a hard no.
In a microwave, metals reflect the energy, but do not absorb it. This creates a spark, or arcing, and can cause burns, damage the microwave or catch fire. Not dramatic. Just true.
If the wire handle pops out easily bend it off if you can. Box will not fit in if the metal is not built in and cannot be removed. Transplant to a plate. Done.
Find out whether there’s a plastic lining
Slide finger down inside. Don’t find it slippery or slightly waxy or plastic-like? That’s a lining. It’s included in lots of takeout boxes as it would be ruined in plain cardboard otherwise.
When wax coatings are exposed to heat they melt and leak in your food. Do not taste good; not something you would like to eat. Some plastic linings are microwave safe and some are not, but yet again, you can’t tell by looking. If you can’t be sure, assume it is not safe! Plate it instead.
Now, fortunately, many better packaging do state the good news. Check for a microwave-safe symbol, typically little wavy lines, on the bottom or side. If it’s there, the manufacturer is telling you that they have tested it. When it doesn’t exist, don’t presume.
What About Plain Brown Kraft Boxes?
These are considered the safer choices, in general. The brown paper that doesn’t have a shiny layer on the inside is called uncoated Kraft paper, and is generally more tolerant of short heating times.
But safe doesn’t mean invulnerable. If left in too long or if it becomes too hot, paper will burn. So when it’s grease soaked in it, that grease will get hot quickly and will smoke. Even on plain Kraft: quick turns, watch, don’t walk away!
As the old saying goes, this is how smart sourcing is crucial for a food business as well. Many brands these days are making custom design take out boxes that are able to fit inside a microwave, and they are clearly labeled so the customer isn’t left wondering on a cold Tuesday night. There is a lot of silent work going on in that little printable symbol.
When serving hot takeout, the actually safe method is to reheat it to a minimum of 165 degrees.
If there’s any doubt, it’s a dull, safe play. Place in a microwave-safe plate or bowl (glass/ceramic), microwave that. It only takes 10 seconds. Avoids all risks mentioned above.
If you have checked the box, there is no metal, microwave-safe label, and you really want to hear it in there anyway, then do it smart: Open the lid, or crack it. The trapped steam can cause pressure to build and a sealed box can explode or warp. Vent it.
Go in short bursts. Repeat this for 30 seconds, then check, stir, repeat. Paper scorches and linings melt after being blasted for three minutes. Watch it. Don’t stray from the kitchen. If you find anything smoky, or not smelling nice, STOP IMMEDIATELY!
Don’t reuse a box over and over in the microwave. A single reheating of fresh leftovers is fine. The heated carton is brittle, and very unpredictable after 5 times heating.
Before you play, check if you’re ready with this card.Use this card to do a quick gut check before playing.
Repeat this in your mind whenever you do it:
1. Any metal, handle, staples, foil lining? If yes, don’t. Plate it.
3. has no microwave-safe symbol and is shiny or waxy on the inside? Don’t risk it. Plate it.
3. Clear label/lid vented / plain kraft? Okay, shorts snitches, watch it.
4. Only takes 2 seconds and saves a ruined dinner or a signed microwave.
Bottom Line
Can paper take-out boxes be microwaved? Some can. Plenty can’t. It’s about metal, lining and you just need to see it and not guess it!
If you’re not sure, a plate will help you out. A plate is your friend when you don’t know. You don’t have to pay anything and get rid of all the uncertainty. If you’re the one purchasing packaging for a business, you can save your customers this headache by purchasing boxes that are heat built and heat labeled. Cold takeout’s annoying. The worst effects of a microwave fire are worse. Take the additional few seconds and you miss both.
