When I went to buy cardboards for a home party the other day, I found a cardboard that said microwaveable!
I didn’t think it was possible to put cardboards in the microwave.
I couldn’t believe my eyes for a moment, but I guess there’s a need for it since it’s commercialized and sold at a reasonable price.
When I think about it, cardboards have recently become more and more solid and made of better materials.
In the past, when you used cardboards for barbecues, they would become soggy because they couldn’t withstand the moisture from the vegetables or the sauce from the grilled meat, but these days cardboards can be used without worry until the end.
It’s no wonder that some people are thinking of heating up leftovers on cardboards.
So what is the difference between microwavable and non-microwavable cardboards?
How It Works in a Microwave Oven?
What determines which containers can and cannot be used in a microwave oven in the first place? If you know this, you’re in luck!
Broadly speaking, it depends on the material of the container and the heat resistance temperature.
Microwave ovens use electromagnetic waves called microwaves to vibrate water and use the frictional heat to heat the entire food. That is why it is called “Microwave” in English.
This is invisible to our eyes because we are talking about the molecular level, but it vibrates 2.45 billion times per second.
These microwaves can penetrate waterless materials such as ceramics and glass, so only the food inside can be heated.
However, like wooden utensils, if the utensil contains water, it cannot be used in a microwave oven because the utensil will expand or crack.
So what about cardboard?
Essentially, the paper is a material that absorbs moisture, so it cannot be used in the microwave.
However, cardboards have a water-resistant surface to prevent moisture from seeping in, so there is no need to worry about moisture for a short time.
Heat Resistance Temperature of the Cardboard
Paper may have the image of burning quickly, but the paper is surprisingly resistant to fire.
However, the paper is surprisingly resistant to fire. Paper itself burns easily if it is set on fire, but if it is heated only by heat, newspapers can burn up to 300 degrees Celsius, and tissues up to 200 degrees Celsius.
So it is surprisingly resistant to heat.
I don’t think many people would try to wrap such a high-temperature item in the paper, but I am a lazy person, and I sometimes put a gratin dish baked hot in the oven at 250 degrees Celsius on a thick sheet of newspaper.
Naturally, there is no problem.
So, cardboard should be fine, too! However, some cardboards have a thin polyethylene film attached to their surface to make them water-resistant.
If Polyethylene Starts to Melt, Is It Harmful to Health?
Everyone cares about their health and the health of their family!
But what if!
What would happen if polyethylene were to dissolve? Will it affect the human body?
Polyethylene is not a problem when simply heating water because it does not exceed the boiling point of water, which is 100℃.
In other words, if it is below 100℃, it is safe.
(This only means that you should keep an eye on the microwave and use it in the microwave for a short time. This is all at your own risk…)
Even so, what will happen if the polyethylene melts at a high temperature?
Even if the polyethylene melts and enters the mouth, it will not be harmful to the human body and will be discharged from the body as it is, so there is no need to worry.
However, even if it is harmless to the human body, there is nothing better than not to eat.
Also, if the polyethylene melts, it means that the water-resistance will be lost, so there is a possibility that the container will be damaged and the contents will leak out, which we want to avoid.
Also, seriously, there is a limit to human understanding, technology, and knowledge.
Especially when it comes to the human body, there are many things we don’t understand.
So, even if it is theoretically safe, no one knows what will happen if even a small amount of it accumulates in the human body.
So please don’t worry about it.
So, why is that cardboard that says “microwave oven OK” OK?
Why Is It Microwavable?
As you may have guessed, the cardboards that are OK in the microwave are products that do not have a polyethylene coating on the surface.
For example, the microwavable cardboards produced by a company called Snap are made of highly water-resistant base paper and can be used safely even without surface treatment.
As for microwaves, all cardboards have a warning that says “only warm-up” or “avoid prolonged use,” so it’s not the same as using a regular plate to warm up, but it’s convenient to be able to warm up a little!
Of course, it is paper, so its strength may be weakened by prolonged use or steam.
Please be careful.
Can Plastic Containers be Heated in the Microwave?
The heat resistance temperature of polyethylene is 110 degrees Celsius, but what kinds of plastics can be used in the microwave?
Each type of plastic has a different heat resistance temperature.
The transparent containers that contain prepared foods are made of polystyrene (PS), which has a heat resistance temperature of around 70 to 90 degrees Celsius.
Therefore, they cannot be used in a microwave oven. If you do use them, they will become crumpled or melt.
Polypropylene (PP) is the most heat-resistant material, with a heat resistance of around 110-130℃.
Most of the bento containers at convenience stores and supermarkets that have microwave heating time written on them are made of PP.
It is easy to remember that if the container says PS, it is not microwavable, and if it says PP, it is microwavable.
However, even if the container is made of polypropylene (PP), the heat resistance temperature is 130℃, and food containing oil will quickly exceed the heat resistance temperature when heated, so be careful about the heating time.
In any case, I would like to point out that the effects on the human body are immeasurable, please do not use them. If you really want to use something, I recommend using cardboards with heat-resistant laminates.