Your plate isn't microwave safe
71This happens most notably when I reheat soup in a ceramic bowl. I suppose the paint isn't safe then?
1To test if a bowl or plate is microwave safe, put a glass of water and the object under test into the microwave and run for a minute. The bowl/plate should be cold. If it's warmed up, it is not microwave safe.
3I do think it has something to go with the glaze they use, but it's been a minute since I researched it.
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If you have a poor quality, low density (often mass produced), ceramic plate, there are tiny air bubbles inside it. These vibrate when the microwave runs, heating the plate faster/more than the food. This is the same reason why some mug handles get hot enough for 2nd or 3rd degree burns in the microwave while others never get the "microwave handle of death". Better made ceramics will have far fewer (or none) of these bubbles. This is why usually hand made pottery will not heat up like this, while factory stuff that was quickly poured into molds often will.
42Often is a stretch. Plenty of the cheap mass produced stuff still doesn't heat up at all. It's almost exclusively older stuff that I notice heating up these days
7That's not how RF works. For one thing, microwaves run at 2.4GHz, which means they can't "see" physical features smaller than a few centimeters (to greatly oversimplify what's going on). The miniscule bubbles simply aren't a big factor.
Rather, what's happening is that the ceramic (probably the glaze if we're honest) has a higher cross section and/or lower specific heat than the food, especially when it's frozen. It absorbs more energy and heats up faster.
I would also expect far fewer and smaller bubbles with industrial slip casting ("pouring into a mold") than manual production.
5I just know that stoneware dishes that I have hand made and fired ( wedging the air out of the clay extremely well) do not ever have this problem, but the light weight, aerated slip cast stuff from mass market stores often does. It cuts across all colors and types of glazes. It really very much seems to be the density of the clay the vessel is made from, which is just another way to say, how aerated it is. The same thing is also observable when it is a dish I have hand made and fired from porcelain, which is why I've assumed it is technique/physical construction and not the actual clay or glaze type. Perhaps instead it is the amount of total vitrification of the clay, which would also affect the density of the finished vessel as well.
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Food is full of water and takes a lot of energy to heat up. The plate is thin and made of easily heated material like ceramic or glass.
29fun fact: water should react most strongly to the radiation used in microwaves while ceramic plates and glass should be pretty much inert - feel free to test by inserting first an empty mug of your choice, then doing the same wirh the mug filled with water and coming back to us with your findings :)
Here is a nice starting point for further reading
also as a side note: metals also react very strongly and the strong reaction of metals combined with the weak reaction of ceramic materials is why microwave kilns are a thing (for an explanation see the appropriate section here under "modern kilns")
32Please note that some ceramics are porous, so they contain water. If you put them in the microwave empty, that water is going to heat up fast and expand. If the water can't get out fast enough, the cup will shatter.
So don't go doing this with your favorite cup and be prepared to give the microwave a proper clean. You don't want any small chips of ceramic in your food.
10water should react most strongly to the radiation used in microwaves
Personal observation says it's coal (graphite, fats). Is this because of induced currents?
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Your plate isn't microwave safe and is absorbing the energy.
26Crazy thing is that I grew up and our family had this plate we microwaved everything with. It NEVER got warm. It was a disposable plate that was not meant to be kept, back when they used high-grade plastic for disposable plates.
I'm sure it was just OOZING carcinogens... but it was cool to the touch after nuking a hot pocket for 30 minutes.
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21Here’s a great video on the Microwave by the Engineer Guy that shows that too.
9Honorary: BILL! BILL! BILL! BILL! BILL! Bill Hammack the Engineer Guy!
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That would imply that there is moisture inside the plate ceramic.
14[Edit: I went and read a scientific article about this and actually a lot I wrote here is wrong. Basically microwaves work by heating the water in the food by making the water molecules oscillate with the waves. (Ref: http://www.sfu.ca/phys/346/121/resources/physics_of_microwave_ovens.pdf skip the part about how a magnetron generates microwaves and how frequencies are limited by the dimensions of the waveguide if all you care about is how the heating works). It's not at all the mechanism I thought and my conclusions are all off. This would mean that as somebody pointed out it's the humidity in the plate causing it to heat, which woukd explain why it happens with earthware.
The bit about which plates work best or not for me is correct as it's experimental, as is the thermal conduction stuff because I actually learned that at Uni rather than presumed from what I knew (a totally different mechanism were photons are actually absorbed, which is not at all how microwaves heat food)]
It's to with the relative ability of materials inside that microwave to absorb that frequency of microwaves: the microwaves just bounce around in that compartment until they get absorbed, and those materials with a higher absorption ability for microwaves at the frequency used in microwave ovens ("microwave" is a whole range of frequencies and those ovens are tuned to emitting just a specific frequency) will end up "taking" a higher proportion of them (and hence of energy) than the other materials and thus heat up more.If the difference in absorption rates is big enough you end up with a situation where one things is absorbing 90% (or a similarly large fraction) of the energy bouncing around as microwaves in that oven and leaving only a smaller fraction for the rest, and hence heating up a lot more.You get a similar thing if you put, say, cheese on toast next to a glass of water in your microwave oven: that cheese, which is mainly fat, will melt like crazy and the water will barelly have heated up, because water is nowhere as good as fat in heating up (I believe, but am not sure, that the actual frequency chosen in the microwave spectrum for use in microwave ovens was the one that fat best absorbs)That plate of yours probably is some kind of ceramic material with metal particles in it, so it's better at absorbing the microwaves than the food, hence the plate captures most of the microwaves (so, most of the energy pumped into that chamber), hence heats up much more than the rest.The termal conduction between the materials with different microwave absorpion rates that heat differently in that microwave will tend to equalize the temperature over time, but unlike with the fat which is part of the food itself and thus will quickly equalize temperature with all the other stuff around it (such as with the water in the food but not, as in my example above, water in a glass which is separated from it), the food and the plate are only in contact is a very limited area (were the food touches the place) so the temperature equalizes much slower between both.
Try a different kind of ceramic (in my experience that problem happens mostly with earthware, so try finer ceramic materials) or glass plates.
In the meanwhile if using the current plates, you can just use a lower power setting in that microwave oven to give more time for the above mentioned process of the temperature equalizing by conduction to move the heat from the plate to the food, spread the food better on the plate to have a higher the area of contact and thus more the thermal conduction for heat transfer between plate and food, or just leave the plate there with the food for a little while after the heating cycle is over so that more of the heat is conducted from the plate to the food before you take it out.
14Ok, now convince that your entire rant wasn't just a language learning model's hallucination of what sounds like a reasonable explanation, but doesn't actually make any sense or have any grounding in reality. Because that's what it sounds like. I was going to start picking apart your explanation, but there's just so much wrong and inconsistent that I gave up.
6Yeah, turns out most of what I thought about the process by which the food heats was bollocks.
Reference: http://www.sfu.ca/phys/346/121/resources/physics_of_microwave_ovens.pdf
I've edited my post.
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If the glaze on a ceramic plate has micro cracks on it, it can cause water to get inside the plate, which then gets hot in the microwave. Throw it away, it can grow bacteria.
13This post brought to you by big dishware
9Sure, I'll throw away all my porcelain dishes
5Porcelain usually isn't glazed and is made from a finer particulate clay allowing it to be smooth and non porous on its own. It's the cheaper ceramics that rely on the glaze to be water proof that are prone to this problem.
If your dishes aren't getting unusually hot in the microwave then they're fine.
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Tempered glass plates ftw
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Twice the time at half the power solves most microwave heating issues.
11The method I do is first I use a water mister to lightly spray the food, cover it, then heat for:
1/2 the original recommended time at full power
1x the recommended time at half power
Let it sit for 30 seconds.
Ex: Says to heat for 2 minutes
1 minute full power
2 minutes at half power
Many microwaves have a method to enter two times and power levels at the same time so you don't have to get up to change the power level.
Doing this, the food typically comes out pretty evenly heated and without significant dry spots.
You can buy the non-metal covers hotels use for their plates online or at a restaurant supply store. Last a lot longer than the crappy plastic covers that are sold as microwave food covers. They're also easier to clean.
The extra moisture from the mister and the cover with a minimal hole helps trap the heated water vapor which should keep the food from getting dried out and help distribute the heat better.
Adjust for you microwave power and how transparent to microwaves your plate cover is. Once you dial it in, it should be the same adjustment for the microwave (ex I add 6 seconds for every minute on mine)
1A misconception about microwaves is that they need around 1000W to actually do sonething, anything lower than 800 makes the waves completely ineffective. When you turn your microwave to 500W, what it actually does is lie to you while microwaving only half of the time instead by cycling on and off. You can usually hear this change in the sound it makes cause it will switch between the 1kW and the ventilator. 🙂
0Pretty sure everyone knows that the power setting on the microwave just changes the duty cycle of the magnetron. I've never seen a microwave specify wattage when selecting power, usually 1-10 or 1-100, no lies involved. What it does is allows the heat more time to evenly distribute through your food while cooking with the same amount of energy. That super hot bowl and tepid soup won't have as much of a difference when it takes twice as long to cook. Hot spots don't get a chance to get as hot. Psychologically it's easier too because let's be honest, no one's waiting 5 minutes after that timer goes off for the heat to settle
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The whole train to use a microwave is that it's fast.
If I'm going to be doubling the time, I'd might as well just pull out the stove or the oven and do it right for just a bit more time.
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I almost always find the solution to microwave reheating issues is to add water before reheating because that's primarily what the microwave is heating up.
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Improperly aligned waveguide.
9Nope, it just doesn't happen. It's an illusion of sorts, the plate isn't being heated because microwaves work essentially on shaking water molecules. Ceramics and plastics are ultra low water content, put a plate in the microwave by itself and it won't be hot.
What you're noticing is the plate heating because the food is heating and the food is transferring heat to the plate, not the other way round.
-1This is true though... Microwaves work around 1000W, at which point we just have enough power to shake one of our losest (in terms of molecules) elements. It's been a while, but I too was taught that the step to heating anything else with microwaves was way too high, but only being able te heat water is enough for most food-related cases as many contain these. (You won't be able to heat up uncooked spaghetti, for example.)
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Your plate has lead in it. Get new plates.
8I've never had this issue
7How does that even happen? I thought only strongly polar molecules interact with microwaves. What exactly in the plate is polar?
7I know why this is! It's multifactorial but the biggest factor is impurities in the plate, especially ceramic plates, that are polar and/or metallic and DO interact with microwaves, absorbing some energy. Since the specific heat (the amount of energy required to raise the temperature of s substance) of the plate material is typically much lower than food, which contains water (which has a very high specific heat), it'll heat up to a pretty high temperature despite not absorbing as much energy. It remains hot as long as it does as it doesn't contain much or any water, unlike your food, which also provides evaporative cooling.
14Melamine plates aren't microwave safe.
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Personally I've found it's quite dependent on the plate color it's actually the reason why all my mugs are black. Red and white really like to exsorbe the microwaves
3Don't use metal-coated plates
3But I like the sparks
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It doesn’t?
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