HOME > Chowhound > Cookware >
What's your latest food quest? Get great advice
TELL US

Is it safe to heat plates in the microwave?

l
la2tokyo Jan 26, 2011 09:51 AM

As someone who works in a restaurant I feel the need to plate everything on a hot plate. At home, where I have no plate heater, I have always preheated my plates in the microwave. I was cooking at my friend's house and I put a stack of plates in the microwave to heat them up, and he expressed a lot of concern. I haven't had any problems before, but I have only tried with the plates in my house, which are mostly from Ikea. Is this a bad idea? Could this damage good china or porcelain?

  1. Upload a photo (10 MB limit)
Delete
  1. j
    jaykayen Jan 26, 2011 09:54 AM

    I'm curious how it works if the plates are dry.

    1 Reply
    1. re: jaykayen
      l
      la2tokyo Jan 26, 2011 09:57 AM

      I was too. But it works. Amazingly well actually. 40 secs to a minute on high and it's the perfect temperature, depending on your microwave. I couldn't believe it the first time I saw it, but I've been doing it ever since. It's the only thing I really use my microwave for.

    2. petek Jan 26, 2011 10:00 AM

      Your plates from Ikea are probably less fragile than fine china or porcelain and some high end china has gold leaf embossed patterns which would definitely cause a problem in a microwave.

      1 Reply
      1. re: petek
        l
        la2tokyo Jan 26, 2011 10:04 AM

        Yeah I never thought of that. I should add that I just realized that I learned this technique at a tiny 12-seat restaurant in Japan where they heated all their plates this way, so there are plates other than Ikea plates that this seems to work fine for.

      2. ttoommyy Jan 26, 2011 10:00 AM

        I used to do this but then I once had a microwaveable bowl crack so I stopped doing it. Now I just hold the plates or bowls over whatever is giving off the most steam on the stove and then place the plates and bowls near the stove (or on a back burner if not being used) until I serve. Usually does the trick.

        2 Replies
        1. re: ttoommyy
          l
          la2tokyo Jan 26, 2011 10:07 AM

          Was that bowl extremely hot when it cracked? As in too hot to hold in your hand? Or did it just crack inexplicably?

          1. re: la2tokyo
            ttoommyy Jan 27, 2011 06:29 AM

            "Or did it just crack inexplicably?"

            That one.

        2. m
          mikie Jan 26, 2011 11:07 AM

          In theory at least, most pottery is microwave transparent and shouldn't heat. For the plates to heat there must be a contaminant in the construction that is a microwave absorber. Or maybe in the absence of other absorbers the plates do absorb some microwave energy. Porcelain, it typically labeled microwave safe, so I would think that should not be a problem. Anything that can go into the microwave with food on it should be safe when there is no food on it.

          Unless we have misinterperted your friends response, perhaps he was not concerned about the plates at all but was concerned about the microwave. I haven't bought a new microwave in a long time, but it seems like they used to tell you not to run it empty. If the plates are truely microwave transparent then in effect the microwave is empty and there is nothing to absorb the microwaves when you turn it on. Thus they would be reflected by the metal cabinet and could potentially damage the microwave.

          9 Replies
          1. re: mikie
            i
            iyc_nyc Jan 26, 2011 07:21 PM

            Hmm, am confused -- I microwave food in my porcelain (apilco and pillivuyt, which I'd think would be less prone to contaminants relatively speaking) and also in stoneware and pottery, and the bowls always come out piping hot (too hot to touch with bare hands) even when the food is not completely hot (?). Can you explain this, or am I misinterpreting the microwave transparent idea?

            1. re: iyc_nyc
              paulj Jan 26, 2011 07:29 PM

              If the bowl is hotter than the contents (especially the rim that is not in contact with any food), you should not be using that bowl in the microwave. If you seal in the steam (with plastic wrap) the bowl will get nearly as hot. But the waves should be heating the food, not the container.

              1. re: paulj
                i
                iyc_nyc Jan 26, 2011 07:39 PM

                Wow. Should Apilco and Pillivuyt be doing this (heating up more than the contents, including at the rims of the bowls/plates where food isn't touching), especially when they are said to be microwave safe? I'm now thoroughly confused, as this happens with ALL my bowls and plates, including those of other materials.

                Does anyone else have experience with this, esp with very common French porcelain that is widely stated (including by the mfr and the retailer) to be microwave safe?

                In case it's relevant, my microwave is a standard GE Spacemaker, and we're talking nothing fancy - just reheating food like pasta or soup at 2-3 minutes max, usually at just 2. After 2 minutes, the food isn't hot enough, the bowl is hot, I stir things up and then might put 1 more minute on it. I don't do 3 straight minutes partly bc I figured early on the bowl/plate would be piping hot after 2 minutes and instinctually seemed bad for the bowl/plate, hence the +1 approach.

                1. re: iyc_nyc
                  tanuki soup Jan 26, 2011 08:30 PM

                  I agree with paulj. If the plate is hotter than the food, it's not a good plate for use in the microwave.

                  I suspect that "microwave SAFE" just means that you can put the dish in the microwave and it won't crack or explode. However, if the dish absorbs microwaves and becomes hot, that means it's also blocking microwaves from the food, which therefore doesn't get hot enough.

                  I microwave on Pyrex or Corelle dishes. The food gets nice and hot, but the edges of the dish are usually cool enough to handle with your bare hands.

                  PS. Of course, if your dish doesn't absorb microwaves at all, trying to warm it in the microwave oven won't accomplish anything!

                  1. re: tanuki soup
                    i
                    iyc_nyc Jan 26, 2011 09:10 PM

                    Okay, I m-wave in pyrex too - and they get hot! I will test this wkend to make sure, but it's something that's so common and all the time that I always use oven mitts - it's hot!

                    1. re: iyc_nyc
                      tanuki soup Jan 26, 2011 09:37 PM

                      If I MW soup in a Pyrex bowl, the bowl will be hot. If I MW a couple of pieces of fried chicken on a Pyrex plate, the rim of the plate will be cool. OTOH, if I MW a serving of lasagna on a Pyrex plate, the rim will be hot. I think it's all about the conduction of heat from the hot food to the bowl or plate. The glass won't be heated directly by the MWs. That's why the rotating turntable in a MW oven is made of glass.

                      1. re: tanuki soup
                        i
                        iyc_nyc Jan 27, 2011 08:17 PM

                        Ok, the turntable example makes total sense and is helpful. I tested tonight (reheating food in apilco) and realized upon removing it from microwave that the rims of the bowl were steamy, no doubt from the food + heat. So this is all consistent with your, Mikie's and Paul's theories.

                        So thanks to all!

                2. re: paulj
                  t
                  themadhousecoffee about 11 hours ago

                  If you cover the top with plastic wrap the plastic is a by-product of petroleum and is toxic. You should NEVER cover anything with plastic wrap and heat it up. It released TOXIC material into your food and air. I use paper towels, wax paper or another plate over the top.

                3. re: iyc_nyc
                  m
                  mikie Jan 27, 2011 05:42 AM

                  Well, I think everyone has taken a good shot at it already, don't know that I can add much. I've got Apilco and Pillivuyt as well, don't notice them getting any hotter than anything else I put in the microwave.

                  Microwave transparent is simpley something that does not absorb microwaves, or at least not very well. The plates fall into this catagory. This short excerpt explains better than I can.
                  "So-called "microwave transparent" materials such as some glass, pottery, paper and most plastics allow the waves to pass through. When used as containers, these materials do not take up microwave energy, but allow the solutions inside of them to absorb the microwaves. The absorbed microwave energy causes dipolar molecules (such as water) to rotate at the rate of 2.45 billion cycles per second. The interaction between the rotating dipolar molecules, ions and non-moving molecules induces friction, which in turn produces the heat that warms the solution. This is somewhat like the way heat is generated when you rub your hands together. Microwaves heat the solutions from the outside in, just like sources of ordinary heating, but much faster."

                  Those molecules are also touching the plate or bowl, so I would expect the plate to heat up, but it still shouldn't be hotter than the food. My personal observation is that heating in a microwave gets the outer layer very hot very quick, but the inner layer never seems to be hot. I think microwave ovens have gotten so powerful that a 1 or 2 min zap has the outside bubeling hot while the inside hasn't had time to warm up. But your plate is touching the outside of what your warming and it's transfering heat.

              2. e
                escondido123 Jan 26, 2011 11:16 AM

                I microwaved some lentil stew on a white IKEA plate and it cracked in two! Looked on the back and it did not say microwave safe, so beware.

                1. paulj Jan 26, 2011 12:42 PM

                  What material are your plates? Correlle ware (essentially glass) does not warm up at all by itself. Melamine does heat up in the microwave, so I avoid using that when reheating food, I was surprised that a earthenware cazuella got hot in the microwave, but then remembered that I had soaked it in water shortly after purchasing (as instructed).

                  If a plate is marked as microwave safe, I would not expect it to warm up at all.

                  4 Replies
                  1. re: paulj
                    e
                    escondido123 Jan 26, 2011 01:06 PM

                    A dry plate that is microwave safe shouldn't get hot, but if you get them wet first the steam will warm them. But you should only do this if the plates are MW safe!

                    1. re: escondido123
                      l
                      la2tokyo Jan 26, 2011 02:32 PM

                      As far as I can remember, every plate I've ever tried to heat in the microwave has gotten hot. I'm not talking only about Ikea plates (which are probably stoneware). They are always dry when I put them in. I understand that microwave energy heats water molecules, but dry plates get hot too. You don't have to take my word for it - try it if you like. Honestly after doing this for a couple years, I don't know what I'd do if for some reason I had to stop. Every time I cook a meal at home I stick all the plates in the microwave two minutes before I plate the food, and it's incredibly easy. I imagine some people may start doing the same thing if they try it after reading this. Unless someone tells me a really compelling reason to stop I don't think I can give up this habit, even if I'm slowly destroying my microwave.

                      1. re: la2tokyo
                        i
                        iyc_nyc Jan 26, 2011 07:44 PM

                        This is consistent with my own experience. Don't heat up empty plates in m-wave, but have found all my plates and bowls get thoroughly and scalding hot, even in areas not touching the food, when the food itself is still lukewarm or hot in some spots and cold in others.

                    2. re: paulj
                      i
                      iyc_nyc Jan 26, 2011 07:25 PM

                      Paul, do you mean with or without food - does that even matter? per my post above, my porcelain and earthenware/stoneware bowls ALWAYS got too hot to touch when reheating food, even when the food is still lukewarm, and even on the rims of the bowls far from the food..

                    3. c
                      CrazyOne Jan 26, 2011 02:22 PM

                      I thought this would cause problem for microwave? That would be my main concern.

                      After a quick search this seems to be generally referenced. In other words, running it dry as in this case (same as empty, really) may be damaging to the magnetron (not definitely, but may). The effect would appear to be cumulative so as you do this more you stand a decent chance of shortening its life.

                      This is how my dad killed one of his earlier ones, a bit prematurely. Well, similar. He used to run it empty to "preheat" it, LOL. I kid you not. After he said that I said no don't do that and he stopped, but I think the damage was done.

                      Now I find the dishes generally do get hot when I use it, but I assume it transfers from the heating of the moisture in the food. If you get serious warmth from heating a dry dish, it calls into question the soundness of the dish (as others have mentioned so far).

                      At the very least, maybe top your stack of plates with a bowl of water? I think that would be a reasonable precaution while possibly still working.

                      1. tanuki soup Jan 26, 2011 03:03 PM

                        IIRC, putting an empty dish in the microwave for 30 seconds or so is the way to test whether it is "microwave safe" or not. If the dish doesn't get hot, it means that it doesn't absorb (i.e., block) microwaves, and can be used for microwave cooking. If it does get hot, it means that the dish blocks the microwaves and the food won't cook properly.

                        Actually, I have also seen special microwave cookware that is intentionally designed so that it DOES heat up in the microwave oven. You put the food (e.g., a fish) on the plate, put it in the microwave, and the plate gets hot and cooks the fish. The idea is that the fish gets nicely browned on the surface from contact with the hot plate.

                        1. l
                          la2tokyo Jan 26, 2011 05:33 PM

                          OK I realized I probably should have google searched this before I posted my question. Google just gave me this answer:

                          Can I warm plates in my microwave oven? — AC

                          Yes, but it's not a good idea. Depending on the type of plate, you can either damage your microwave oven or damage the plate.

                          If a plate is "microwave safe," it will barely absorb the microwaves and heat extremely slowly. In effect, the microwave oven will be operating empty and the electromagnetic fields inside it will build up to extremely high levels. Since the walls of the oven are mirrorlike and the plate is almost perfectly transparent to microwaves, the electromagnetic waves streaming out of the oven's magnetron tube bounce around endlessly inside the oven's cooking chamber. The resulting intense fields can produce various types of electric breakdown along the walls of the cooking chamber and thereby damage the surface with burns or arcs. Furthermore, the intense microwaves in the cooking chamber will reflect back into the magnetron and can upset its internal oscillations so that it doesn't function properly. Although magnetrons are astonishingly robust and long-lived, they don't appreciate having to reabsorb their own emitted microwaves. In short, your plates will heat up slowly and you'll be aging your microwave oven in the process. You could wet the plates before putting them in the microwave oven to speed the heating and decrease the wear-and-tear on the magnetron, but then you'd have to dry the plates before use.

                          If a plate isn't "microwave safe," then it will absorb microwaves and heat relatively quickly. If it absorbs the microwaves uniformly and well, then you can probably warm it to the desired temperature without any problems as long as you know exactly how many seconds it takes and adjust for the total number of plates you're warming. If you heat a plate too long, bad things will happen. It may only amount to burning your fingers, but some plates can't take high temperatures without melting, cracking, or popping. Unglazed ceramics that have soaked up lots of water will heat rapidly because water absorbs microwaves strongly. Water trapped in pores in such ceramics can transform into high-pressure steam, a result that doesn't seem safe to me. And if a plate absorbs microwaves nonuniformly, then you'll get hotspots or burned spots on the plate. Metalized decorations on a plate will simply burn up and blacken the plate. Cracks that contain water will overheat and the resulting thermal stresses will extend the cracks further. So this type of heating can be stressful to the plates.

                          _______________________________________________________

                          Even now that I know this I don't know if I can stop. I wish someone would invent a plate warmer that is as convenient as a microwave.

                          9 Replies
                          1. re: la2tokyo
                            j
                            jaykayen Jan 26, 2011 07:30 PM

                            What's wrong with the oven, like you do at work?

                            1. re: jaykayen
                              l
                              la2tokyo Jan 26, 2011 07:44 PM

                              It takes ten minutes to heat it up. If I make something small like scrambled eggs for breakfast, the eggs would be done in ninety seconds and the plates would take ten. I think putting the plates under hot running water is probably the next best choice if the oven's not on. The problem with that is that if you have four plates stacked up it's not as effective, then you have to dry them etc., etc.. It seems stupid to complain about something that takes twenty seconds, but when I do it every day and there's an easier way it starts to nag at me. I guess I'm a little anal.

                              1. re: la2tokyo
                                s
                                souvenir Jan 27, 2011 08:35 AM

                                Hopefully it doesn't take 10 minutes for your oven to heat up to 170-200 degrees? When I remember, and I am trying to get into the habit, I put plates in and turn on the oven at the same time I am turning the heat on a pan to start a quick dish. When I am using bowls or cups, I turn on the tea kettle rather than the oven.

                                1. re: la2tokyo
                                  SanityRemoved Jan 28, 2011 04:14 AM

                                  How about a damp paper towel over the plate in the microwave? That would give it something besides the plate to act on. Of course the paper towel is going to be steaming hot.

                                  I wonder how fast those portable warming lamps take to heat up an empty plate?

                                  1. re: SanityRemoved
                                    l
                                    la2tokyo Jan 28, 2011 08:45 AM

                                    This morning when I mad my eggs I splashed some water onto the plate and zapped it for a minute. Of course the plate got hot. I knew it would get hot because it gets hot even when there's nothing on it. But, as I did it, the whole thing seemed kind of silly to me. If my plates are heating up, then going by most of what I've read, they're not microwave safe. So I'm probably not supposed to be using them. If they are microwave safe, then the levels of microwaves in the oven are reaching levels so high that they are damaging the microwave, but a splash of water or a damp paper towel is going to make it all OK? I think almost all the plates I've ever had get hot in the microwave, and therefore are not really 100% "microwave safe." According to the above editorial I can probably warm it if I know how long it takes without any problems, so I'll keep doing it. I will report back here when my microwave breaks or the first plate explodes. So far it's been 18 months with this microwave and I've been doing it almost every day. I don't care if my magnetron "doesn't appreciate having to absorb it's own microwaves." I don't appreciate eating an omelet off of an ice cold plate.

                                    1. re: la2tokyo
                                      l
                                      la2tokyo Jan 28, 2011 09:04 AM

                                      BTW I just checked the Ikea website and it says all these plates that I have been heating in the microwave are "microwave safe."

                                      1. re: la2tokyo
                                        paulj Jan 28, 2011 09:07 AM

                                        What does the manual for you microwave say? Does it warn against running it empty?

                                        The warnings about running the machine empty, or with metal items inside probably apply more to old machines than newer ones. Manufacturers might have added sensors that cut the power in problem situations.

                                        1. re: la2tokyo
                                          m
                                          mikie Jan 28, 2011 09:13 AM

                                          Don't confuse "microwave safe" with microwave transparent. Items can be microwave safe and not be totally microwave transparent. The problem exhists when the item is a microwave absorber, ore worse yet reflector, that's when there are more issues. I know this is splitting hairs a bit, but there are obviously levels of microwave transparancy as there is levels of microwave absorbancy. It may still not be great for the microwave, but obviously since it's worked for 18 months, it's not like putting a can of spagetti-Os in there to heat up.

                                          1. re: mikie
                                            l
                                            la2tokyo Jan 28, 2011 09:19 AM

                                            As an aside, I saw someone heat something in a stainless bowl in the microwave one time. It was sparking a lot. I freaked out but he told me he does it all the time and nothing bad ever happened. He was a total idiot, which is why I believed him when he said he did it regularly. This is a true story. Maybe I'm a similar idiot.

                                2. c
                                  Chipped Ham Jan 28, 2011 12:25 PM

                                  Could there be lead in the glaze or ceramic and that's what's heating up the plate?

                                  1. s
                                    subal about 7 hours ago

                                    In addition to the other comments here, I would be concerned about non uniform heating of ceramic/china plates as it could induce cracking!

                                    1. eLizard 33 minutes ago

                                      i run plates/pasta bowls under hot water and dry.

                                      Show Hidden Posts