• Lesrid@lemm.ee
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      9 months ago

      This happens most notably when I reheat soup in a ceramic bowl. I suppose the paint isn’t safe then?

      • na_th_an@lemmy.world
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        9 months ago

        To 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.

  • Someology@lemmy.world
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    9 months ago

    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.

    • Misconduct@startrek.website
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      9 months ago

      Often 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

    • AlotOfReading@lemmy.world
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      9 months ago

      That’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.

      • Someology@lemmy.world
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        9 months ago

        I 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.

  • TheOneCurly@lemmy.theonecurly.page
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    9 months ago

    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.

    • knorke3@lemm.ee
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      9 months ago

      fun 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”)

      • Thorry84@feddit.nl
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        9 months ago

        Please 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.

      • MonkderZweite@feddit.ch
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        9 months ago

        water should react most strongly to the radiation used in microwaves

        Personal observation says it’s coal (graphite, fats). Is this because of induced currents?

    • abraxas@sh.itjust.works
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      9 months ago

      Crazy 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.

  • Traegs@lemmy.world
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    9 months ago

    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.

      • Traegs@lemmy.world
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        9 months ago

        Porcelain 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.

        • Someology@lemmy.world
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          9 months ago

          No, porcelain is usually glazed, just often with clear glaze, since it is already white to begin with. If the porcelain is shiny, then it is glazed.

  • Aceticon@lemmy.world
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    9 months ago

    [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.

    • ElderWendigo@sh.itjust.works
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      9 months ago

      Ok, 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.

  • Psythik@lemm.ee
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    9 months ago

    Twice the time at half the power solves most microwave heating issues.

    • LordOfTheChia@lemmy.world
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      9 months ago

      The 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)

    • Doctor xNo@r.nf
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      9 months ago

      A 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. 🙂

      • DeusHircus@lemmy.zip
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        9 months ago

        Pretty 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

        • Doctor xNo@r.nf
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          9 months ago

          My current one did before it broke and my last one also went from 250W to 1000W on the button… I know it’s the same at a friend’s and at work too cause we had the discussion about it there too a few months ago… Maybe it’s a Europe thing? Or maybe I’m just in a random cluster. 🤷‍♂️

    • chiliedogg@lemmy.world
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      9 months ago

      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.

      • Psythik@lemm.ee
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        9 months ago

        And I thought I was impatient…

        It’s still faster than a stove/oven. You’re being ridiculous.

        Whatever; not my problem. Go ahead and keep burning yourself on hot plates and enjoying food with cold spots. You do you.

        • chiliedogg@lemmy.world
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          9 months ago

          I’m saying that cooking something for 6 minutes instead of 3 in the microwave is getting close enough that I’d might as well use a pan and cook it in 8 minutes for an even better result.

          If something tends to microwave poorly, it probably shouldn’t be cooked in the microwave at all.

          • criitz@reddthat.com
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            8 months ago

            Generally… If it took 3 mins in the microwave you’re looking at way more time using the oven than 8 minutes. Doubling microwave time should still be significantly faster than using an oven, especially considering preheating time.

  • aesthelete@lemmy.world
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    9 months ago

    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.

    • Madison420@lemmy.world
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      9 months ago

      Nope, 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.

      • starman2112@sh.itjust.works
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        9 months ago

        A simple refutation is that metal gets hot in the microwave, and it has no water in it. Microwave radiation heats many things, not just water

        • Doctor xNo@r.nf
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          9 months ago

          Only at the points it discharges the waves electrically. All the rest of the metal usually stays quite cold,… I’ve taken out plenty of forgotten spoons in my lifetime. 😅 Hence why microwavable metal is a thing. (Like the metal rack the usualky cones with combi-ovens.) Metal is a good heatconductor though, so microwavable metal will easily get hotter than the food heating it (much like your car’s metal exterior getting hotter from the sun than it’s environment), yet if you microwave that metal on its own it will not heat up at all…

          • starman2112@sh.itjust.works
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            9 months ago

            Metal is a good heatconductor though, so microwavable metal will easily get hotter than the food heating it

            That’s… not how heat conduction works. Something can’t get hotter than the thing that’s heating it. What’s heating the metal is the microwave radiation.

            yet if you microwave that metal on its own it will not heat up at all…

            But

            It does

            Metal that’s designed to be part of the microwave, like a rack or the walls, is designed specifically to avoid heating up. But like, a spoon by itself on the turntable will definitely get hot if you microwave it

            • Doctor xNo@r.nf
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              9 months ago

              It was simplified for ease. Metal indeed does not actually get hotter than its environment, but due to it’s heat conductivity it has the ability to relay any surrounding heat when any spot gets cooled down (like when you touch it), it will transfer surrounding heat-energy to the colder spot, which it can do better than most other materials.

              Either way, any spoon I ever accidentally microwaved remained quite cold tbh, though I have not tested this out over extended periods of time. Any heated food touching it will still be the main source it will draw energy from when touched, though…

              • starman2112@sh.itjust.works
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                9 months ago

                I don’t know how we manage to live under different laws of physics then, because I have definitely touched metal that had been in the microwave and gotten hot, and there are videos of people putting metal in the microwave showing it getting hot without sparking. Unless me, everyone I know, those guys, and all their commenters are all lying, metal will most definitely get hot in the microwave

                Am I getting sharks are smoothed?

                • Doctor xNo@r.nf
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                  9 months ago

                  Yeah, if you look it up on Google you will find above definition, though… 🤷‍♂️

        • Madison420@lemmy.world
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          9 months ago

          Different principle entirely but ask a physicist, I’m not telling you to trust me. I’m telling you to look, learn, and experiment.

          Ed: Here’s a hint. The first microwave was called a radarrange.

          • starman2112@sh.itjust.works
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            9 months ago

            But I have experimented… I’ve melted plastic spoons in the microwave before. Where’s the water in plastic?

            Edit: that’s not really a hint. What does radar have to do with how microwaves heat things?

            • Madison420@lemmy.world
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              9 months ago

              Those aren’t microwave safe then, other materials react as well but microwaves are tuned to shame water really well and most everything else not as well.

              Yes it is. Microwaves came from radar and radar works on the same principal.

              Ed:

              In 1945, the heating effect of a high-power microwave beam was accidentally discovered by Percy Spencer, an American self-taught engineer from Howland, Maine. Employed by Raytheon at the time, he noticed that microwaves from an active radar set he was working on started to melt a Mr. Goodbar candy bar he had in his pocket. The first food deliberately cooked with Spencer’s microwave oven was popcorn, and the second was an egg, which exploded in the face of one of the experimenters.[12][13]

              To verify his finding, Spencer created a high-density electromagnetic field by feeding microwave power from a magnetron into a metal box from which it had no way to escape. When food was placed in the box with the microwave energy, the temperature of the food rose rapidly. On 8 October 1945, Raytheon filed a United States patent application for Spencer’s microwave cooking process, and an oven that heated food using microwave energy from a magnetron was soon placed in a Boston restaurant for testing.

      • Someology@lemmy.world
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        9 months ago

        It’s the many tiny air bubbles trapped in low quality ceramics that vibrate and heat it up.

        • Madison420@lemmy.world
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          9 months ago

          Possibly, feldspar content can have an effect as well in ceramic but in general the plate is not doing the heating or being heated. An ideal ceramic plate or plastic plate doesn’t heat until you get real crazy and manage to hit a frequency it likes.

      • Doctor xNo@r.nf
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        9 months ago

        This 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.)

        • Madison420@lemmy.world
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          9 months ago

          I know, for the most part talking science is like talking to a wall but it’s pretty gratifying when someone finds it and is randomly excited.

  • RoyaltyInTraining@lemmy.world
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    9 months ago

    How does that even happen? I thought only strongly polar molecules interact with microwaves. What exactly in the plate is polar?

    • Aleric@lemmy.world
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      9 months ago

      I 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.

  • credit crazy@lemmy.world
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    9 months ago

    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