Should I cover food while reheating it in a microwave?

Question

For reasons of time, I like to cook more than one portion of a meal and then reheat a portion in the microwave whenever it's needed.

Aiming for maximum energy efficiency, I wonder if it's a good idea to cover the food with a big ceramic or glass bowl?

Just in case this is somehow relevant, here are my two main thoughts which led me to ask this question:

Covering might be good because the developing steam is concentrated in a small volume and gives off more of its heat to the food.
Covering might be bad because the bowl partly reflects the microwaves, and therefore a part of the energy never reaches the food.

Wayfaring Stranger · Accepted Answer

You do get some reflection of microwaves off a glass or plastic cover (Table 1 here)

Material    Reflection  Transmission
    Metal       0.88         0.00
    Glass       0.38         0.60
    Plexiglas   0.16         0.83

Don't use metal lids. Neither glass nor Plexiglass plastic absorb much of the beam.

The question then becomes: Does reflection off a lid slow heating more than retaining heat in an enclosed vessel speeds it?
Anecdotal, but experience tells me that using a plate over a bowl or a casserole dish cover routinely gives hotter, more uniformly heated food. Probably true for plastic wrap too, but I don't use that in a microwave since I had a piece of it melt on me.

monroec · Answer

If I am reheating something like rice, than having saran wrap over it in the microwave adds moisture and aids in the reheating and subsequent moisture of the rice. I guess I have always had better luck having saran wrap over anything that may dry out a bit; rice, chicken, beef etc. Don't see how it could really do any Harm. Personal preference more than anything.

Answered by monroec on March 19, 2021

Robert · Answer

I use the cover because it's easier to clean than the microwave if something splatters.

rdt2 · Answer

I always cover food when reheating it in a microwave, for several reasons:

it prevents mess in the event of an explosion (particularly so with soup).
it prevents the food from drying out.

Lay the cover on lightly (perhaps with a small non-metal weight on top to hold it in place) or puncture it (if using cling-film):  this allows air/steam to flow out of the container if pressure develops when heating (which helps avoid said explosions), and flow into the container when you remove it from the oven (cling-film is particularly adept at shrinking back down onto the food).

For the lid, experiment!   Try a saucer, plate, glass, plastic, whatever until you get something that won't itself get too hot to let you lift it out. Try ANYTHING BUT METAL.   I usually use a plastic lid saved from some old food container.

fenuedward · Answer

no. this is becouse when food is been cover in a close container, the heat that is generated become too high. as it.become higher and higher, the vapour in the container will be force to move out and it lead to explusion.

Answered by fenuedward on March 19, 2021

Should I cover food while reheating it in a microwave?

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