This makes so much sense to me now. I can confirm this used to be a problem!! My mum had exactly this experience with a late 70's early 80's Rank Arena microwave without a turntable. She heated a mug of water to make her coffee one morning, as soon as she went to take it out of the microwave, or she may have just put a spoon in it to stir the water, the water instantly exploded. Luckily she wasn't seriously burned, she must have had super fast reflexes, and the roof of the microwave took most of the hit😲

A funny story..... My father was USAF during WWII and Korea. He said that guys would put their waxed paper (common before lots of plastics) wrapped sandwiches in the fixed giant radar dishes and sometimes later enjoy a hot lunch. I guess the first Radar Ranges were courtesy of Uncle Sam :).

Many old microwave ovens had what looked like an unpainted fan in the top interior that in reality was a deflector for the microwave beam, serving to sweep the beam throughout the interior of the enclosure. This had the unfortunate effect of requiring the microwaves to enter from the top, which reduced the useful interior volume and added the expense of a microwave waveguide. The lazy susan was added to simplify the overall system, as it could be driven by the same motor used to drive the fan that cooled the microwave source and power supply. Plus, the lazy susan mechanism was less expensive than a waveguide, as the raw beam could be dumped in from the side, with little regard for beam shape or uniformity. Today's multi-mode microwave ovens (that include, say, an air-fryer or convection capability) can't use the lazy susan, and instead use beam forming, sweeping and interior reflection to help ensure uniform cooking.

I always thought it was to prevent hot and cold spots in food due to standing waves inside the oven. I've seen microwave ovens with a rotating reflector at the top of the oven which I thought was a clever way to prevent standing waves, or at least stir them around a bit.

In the 70's I was at a snack bar at an Air Force base and heard a loud pop and a scream. A guy bit into a peeled hard boiled egg he'd heated in a microwave. He got hospitalized with stream burns in that mouth and on his face.

My parent's had a microwave without the spinning twirly-ma-jigger and I remember being told to not put an egg in a microwave because it will explode. Well, I thought that was just nonsense 😄 ... soooo one day I put one in there for 30 seconds (nothing happened) and then another 30 seconds (again nothing), I did that again and I pulled the plate out of the microwave to further examine the egg. I noticed that it was sweating and I saw a tiny crack in the shell. I grabbed a toothpick and gently poked it into that crack ... **KA-BLAMMO!!!** , it eggsploded like a grenade 😄🤣 ... egg and shell all over me and the kitchen. I then proceeded to clean up the scene of the crime. The following day I was talking with my mom (in the kitchen) and suddenly she looked up and said "How in the world did eggshells get all the way up on the ceiling?". I tilted my head and said "Hmmm, that is rather odd isn't it?". I quickly changed the subject 😄🤣😄🤣

Our 1970s microwave did not have a carousel. Every one I've used since has had one. I always thought it was to ensure even heating, but the lawsuit angle makes much, much, much more sense. Thank you for reaffirming my cynicism, Fran! Functionality < liability.

I seem to remember back in the seventies when the rotating platter was being introduced, microwave oven manufacturers claimed it was added to more uniformly heat the item with no mention of it being added as a safety feature to eliminate the dangers of superheating.

Also sometimes happens with my induction cook top when heating up water in a non-stick pan. There is no sound, but as soon as you pour out the water it *instantly* boils viciously! A very weird (and frightening) phenomenon.

We got our first microwave, a big woodgrain Kenmore, in '85. No turntable, but it did have a temp probe, so you could set it to cook to a set temperature. Worked perfectly with only a couple lightbulb changes until 2012.

My wife and I were given a microwave as a wedding gift in '75. With the extensive shielding required back then, it weighed as much as a small car. I also remember seeing the apple desert in a TV dinner bubbling next to frozen potatoes. Without the turntable found in modern units, we had to turn everything by hand.

One of the few things I remember from chemistry lab: boiling distilled water in new glassware can do this. It is called "bumping". Scratch the bottom of the vessel with something metal so there is an edge for the the boil to "seed". You can use glass chips, too, but that's a very bad idea in the kitchen.

Bravo Fram, Bravo! - Please, go ahead and take bow... - - To recognize and acknowledge my applause praising this video.

I think the biggest risk factor is heating the water to boiling, letting it cool a bit, then heating it again. When you heat it the first time dissolved gases come out of solution first, creating bubbles that act as nucleation points for the subsequent boiling. But once it's boiling those dissolved gases get carried to the surface, so they can't form bubbles for the second heating. Pits, cracks, and scratches help by trapping a bit of vapor when the bubble breaks loose, so the nucleation point is preserved, but if they're filled with liquid they don't act as nucleation points, you still need a gas-liquid boundary for that.

Fun fact, in the Netherlands, where Philips introduced the first domestic microwave ovens, they were branded/named after the microwave tube in it, the magnetron. Hence, in contrast to just about every language where its name is a translation of micro-wave (oven), in Dutch the appliance is called a magnetron. As another commenter remarked, I also remember there was a second reason for the revolving plateau, the standing wave pattern that forms inside the microwave oven creates uneven heating, so one could end up with for example meat that was well heated/cooked in spots but cold and raw in other spots, which could cause problems with bacteria or parasites that were not killed, leading to infections or food poisonings.

Here the recipe for a superheat water that worked for me. I discovered it by myself a long time ago. As I was testing the brand new first microwave my mum ever get, I found fascinating to see water boiling "by itself" So I put a coffee cup half filled with water nicely centred and start the microwave to see it boil. It usually take 40 second and after seeing the bubbles I stopped the microwave and let the cup inside. I do this a couple time, this allow the dirts (calcium) to sit at the bottom of the cup and thanks to the closed door, no dust fall in. Just before bed I give a last try, but after 50 second (it was an electronic digital control with count down) the water wasn't hot enough to boil. I was afraid to have broken the brand new microwave just by doing this multiple time. My nose was stuck on the door when the steam explosion occur seconds later! The amount of water was low and the superheat not to high, so no damage as all stay into the microwave, but what a burst ! So don't do it it can be really dangerous, and if you do, (as I know some will) put only a small amount of water like 12 millilitre of water (size of a ristretto) to limit the power of the burst, and if nothing happen let it cool, never try to poke it and don't apply heat more than 50% it take to boil (if it boil in 30 sec don't go further than 45 sec) as the energy put over the boiling temperature will be liberate in microsecond, it can be really powerful even blasting the door open. Even with these precaution it's dangerous, again let's someone stupid do this ! It happen by accident, and never did it again after knowing what happen

I’ve actually experienced this first-hand. Literally. It was a cheap-o brand microwave, don’t remember whether the table was just broken and didn’t spin or if it didn’t have a rotating tray or what. But I was heating up a plastic cup of water, and when I reached in to grab it - it went absolutely nuts. Started boiling vigorously right as I grabbed it and spilled over the edges burning the backside of my hand. Terrible experience. 1/10. Do not recommend. At the time I wrote it off as a freak accident, justifying it that perhaps it simply started boiling at the very moment that I opened the door. One of those “perfect timing” type things. Turns out it’s even weirder than that. This is actually really cool. I mean the scientific reasoning behind the occurrence. The more you know. Thanks for this nugget of knowledge!

A similar phenomenon: Supercooling, where very pure water in a very smooth container will remain in the liquid state even if the temperature is under the freezing point. Then, a slight disturbance will trigger the cristallisation, where all the water turns to ice in a few seconds.

My first experience with a microwave oven was in the Pentagon in the 70's . My uncle was stationed there and we had a guided tour. The galley included a microwave oven for limited menu items.

Thank you Fran for explaining super heating in a microwave oven. As a retired electronics technician that once worked servicing commercial microwave ovens, I am familiar with the issue. However there is a little more to that story. Original designs of microwave ovens had the signal entering the cavity (area where items were heated) from the top. The RF signal was ducted from the magnatron tube to the cavity via a waveguide. Both the waveguide and cavity were finely tuned to the microwave frequency in order to achieve maximum heating of objects inside the cavity. Unfortunately the RF wasn't evenly distributed within the cavity and "Hot Spots" were experienced. In order to overcome this situation a plastic cover or sometimes a plastic dome was added to the inside of the cavity top. Under this plastic cover was a rotating antenna that reflected the microwaves and helped to more evenly distribute the microwaves within the total cavity. This rotating antenna was known as the "Stirrer" It basically stirred the microwave signals while heating the item in the cavity. As microwave ovens evolved, and sometimes super heating was happening, it was determined that costs could be reduced and the waveguide and stirrer could be eliminated by placing the RF port on the side of the cavity instead of on top. This alro reduced the overall height of the ovens. When that happened, in order to prevent "Hot Spots" and super heating, they came up with the idea to rotate the item to be heated thus solving both issues. Most all current microwave ovens have the RF enter from the side with rotating trays in the bottom as described in your video. Some models used to have switch settings that permitted the user to disable the tray rotation. I'm not sure if that engineering practice still exists. That would be something worth looking into. Thanks again for explaining the things you do.

Hi, Fran - our new Panasonic microwave doesn't have a turntable, or rotisserie as you call it. I could be wrong, but I understand that it's a relatively new design in which the antenna itself rotates under the flat bed of the oven.

I have a probably 12-year old, over the counter microwave that has no rotary table. I picked up a vintage wind up rotisserie for it. Many of the early microwaves had what looked like a metal fan on the output of the magnetron. That was there to spread the microwaves around to prevent hot spots. So, adding a rotisserie was low added cost; just remove the fan and motor and put in a rotisserie.

I remember the very first Radar Range I saw...it was in 1966 in the kitchen of a wealthy family in Oahu whose dad was a scientist working for Raytheon. It blew my young mind. I remember this as if it were yesterday.

Always heard those things called a turntable or carousel, not a rotisserie like the rotisserie chicken cookers at Costco. Anyway, the primary reason for the carousel was to make cooking more even. Uneven cooking was a major problem with microwaves up into the 80s and made microwave food a joke. And it stayed that way until the 80s when very smart engineers were able to do a better job tuning the wave guides and adding fuzzy logic to the controllers. But the carousel was a simple, low tech and cheap way of dealing with the issue while at the same time commanding a premium price at retail.

You can still superheat water with a rotary microwave. I've accidentally done it several times over the years. Fortunately not energetic enough to shatter glass and spray scalding water all over me, but it certainly scared me when the container of water flash boiled when disturbed. All our microwaves have had turntables, every time it's happened the water had been boiled, left for a while then 'reheated'. I've even managed to get the container out of the microwave and then had it 'explode' when a spoon or ingredient was added.

It may reduce the probability but it certainly doesn't eliminate it- about a year ago I managed to super-reheat a cup of coffee in a not-particularly-clean cup, made with fairly hard water, in a very carousel-equipped 2012-model microwave. I was handling it carefully so as to avoid spillage, so It didn't go foom until after I had it out of the 'wave started to put a spoon into the cup, in anticipation of stirring in yet-to-be-added cream. Fortunately there weren't any injuries, nor even a big mess, as I'd happened to set the cup on a plate that caught most of the overflow. I think one reason reheating a hot beverage is so hazardous is the lack of dissolved gases in the previously-boiled water, which reduces the available nucleation sites, making it harder for the water to begin boiling again. This wouldn't be a problem in a conventional heating container, as you said, but the microwave does its thing... differently.

I had heard a couple of times, maybe in the 90s, of liquid exploding when taking it out of the microwave. However, I never knew of it happening to someone I knew, or in my house. So after a few years I kind of just forgot about it and in the back of my mind took it as a kind of urban legend. I always thought the rotating plate was purely for even heat until now. We got our first microwave around 1978 as well. At that time no one I knew had one. Couple of years later lots of people started getting them.

whoa - it would seem like this should be grade school science - evidently, not so, at least during my school years - - I'm in my 70's and have never heard of the "surface tension / super heating" phenomenon before - - fascinating - - thank you Fran.

My parents got an Amana Radarange around 1980. I remember it being the first time I saw a membrane style keypad. It had a heavy glass dish that sat in a recess in the floor of the interior and the rather unusual bottom hinge door.

This happens to me quite often in my turntable mw when I use a Pyrex measuring cup to heat water and miscalculate the amount of time to heat by just a little bit. if I'm adding anything to it. it will explosively boil over. I've just learned to add a tiny amount of whatever and it fizzes up less violently and then it's done and I can add the rest of whatever. (usually Cocoa or bouillon powder). if I just way over blow the time I will usually hear a pop and the pyrex plinking on the turntable and of course there's water everywhere.

The power injection of the magnetron came on one side creating hot spots. Microwaves used a stirrer hidden either above or below the chamber. But as time went on people got tired of turning their food every minute to even the heating. The turntable proved to be much more effective so became the standard. The turntable solved two problems at the same time.

Fascinating. - Sidenote; our first Kenmore didn't turn off when you opened the door!

I've worked in various Cafe kitchens in the UK, and none have had a turntable.

I just want to say "Fran, you are awesome". Thanks for being you

It might be that the average consumer has not run into superheating. Mostly because everything that they use has some sort of scratch on the surface. This is where nucleation points for boiling can begin. If you went into high school chemistry it was one of the safety points at my high school. You always had to put boiling stones into the bottom of your test tube to prevent catastrophic superheating. Superheating can still occur in microwaves that have turntables in them. The solution is to put some scratches into your glass and ceramics. They don't have to be huge they just have to be some place or boiling point can begin

I have seen this phenomenon. I had a mug of water in the microwave too long. when I reached in to pick up the mug, the water in it suddenly exploded in a rapid and intense boiling that splashed some hot water on my hand. It was quite painful.

Hi Fran. I have two microwave ovens. One of them is really old and the other one is quite modern. The older one is an Amana Radarange Touchmatic from probably the 1980s. It's big, heavy and square. It's built like a tank. My cousin gave it to me back around 1998. He owned a bunch of microwave ovens back then. He lived in a large apartment building where many retired folks lived. People in his apartment house would give him their old microwave ovens when they bought new ones. The one he gave me is so heavy that it takes two strong people to move it. lol. It doesn't have a built in rotisserie. I use one of those manual winding rotisseries that works very well. I've used the oven and the plastic rotisserie for 24 years and neither of them have ever broken. Thanks for the info in this video. I had no idea water could get that hot without boiling and steaming. I'll be careful not to do that in my ancient Radarange oven.

You can still get a cup of microwaved water slightly overheated. But it does not explode till you put a teaspoon of sugar in it. And even at that, it just boils up, it doesn't explode.

I didn't know about the rotation. But a borosilicate tea glass once exploded in my microwave oven despite being rotated. The door flew open with a bang, no one was hurt, the microwave oven was not damaged. And is still working properly. It is made in the UK and has been in daily use since 1990. I think the delayed-boiling explosion happened to me because I first brought the water to simmer and then heated it again to get it a little hotter. By simmer, the water was gas-free and could overheat, even to the point of exploding. It is better to boil water in an electric kettle, which uses almost half the energy of a microwave. Microwaves are ideal for heating food, milk and the like.

Sharp had a patent on the turntable. Where I work commercial microwaves in the cafeteria for employees to use do not have turntables.

Will add that the superheating takes place in the bulk fluid, making a volume of fluid that, is going to get hotter and hotter, as the microwaves set up a standing wave in the cavity, so this pattern does not move around much other than jitter at mains frequency with the FM modulation of the basic microwaves. thus the turntable, there to ensure the food is stirred through the pattern, so all parts will get more or less even heating. Incidentally I have a microwave with no turntable in it, it has a flat glass rectangle in it as base, but up under the roof is a large plastic microwave transparent window, which has inside it the waveguide outlet, and as well a stirrer fan, driven by the airflow over the magnetron cooling fins, which turns this light steel blade around, so the microwave radiation pattern in the cavity gets swept around, instead of the turntable and static wave pattern. However the blade is a lot more complex, and takes up a lot of room in the roof, and needs a big plastic cover over it, so the cheaper option of the round turntable, with the pancake motor to turn it, won out, as that is a lot easier to scale up in size, and the rotation does result in more even cooking, as the radiation pattern in the centre of the oven will be more even that at the edges. First microwave in the family was around 1979, when Dad brought home a brand new Sharp convection microwave, which, in addition to having an all stainless steel interior, also had a convection oven element in the cavity, and a microwave oven built in, so you could do things like cakes, where the microwave did most of the cooking, and the convection side would result in a perfectly browned exterior of the food, be it bread, cake or a roast. Biggest drawback was that this was also "self cleaning", which was actually the roof being made from coated mild steel, and this rusted out. Not a problem, my father ground off all those spot welds holding the top on, and fashioned a new cover for the top of the cavity, made from stainless steel perforated plate, welded in to the existing cavity walls, and then the heating element assembly, along with the new non rusted convection fan, was screwed back on top of it. I currently have a regular small microwave with turntable, but also a 1980 made KIC microwave, with no turntable, and the aforementioned stirrer, that has done sterling work over the years, a great buy for the $4 I paid for it as a beige and brown box on auction in the 1990's, and it is still going strong. Small one is heavier than the big, as it is made with actual steel plate, not the thin foil of the new ones, and has a power transformer made with real copper windings all over, not the undersized and CCA wire the current ones use.

In order to be a patron, one needs to be employed to pay you. I whipped out my MythBusters DVD, they used a turn table microwave oven to superheat distilled water. So, I don't know about the turn table (rotisserie) theory holds up.

My Parents had the 1980 version of this Amana. It had a fantastic "touch control" keypad, much like those sensitive touch-dimmer switches of the 80s. Worked great! Had the 1/8" jack for the "temperature probe". Since that era, I despise every lousy membrane keypad on basically ALL modern ovens, despite other improvements.

Both of my parents saw demonstrations of radar ranges when they were little kids (they were both born in 1944) in fact, mom got to taste a potato cooked in just a few minutes. My mother finally got her own microwave in the early 1980's. It was cool, but not what she expected.

My experience is that moving the water-filled pot around does not prevent superheating. I thought the rotating plate was to provide more even cooking, which is necessary on the cheaper microwoave-emitting mechanisms that are quite uneven. I have a glass pouring kettle that I use to make coffee with a pour-over system. It's new, and not used for anything other than heating and pouring plain water, so the inside glass is rather smooth and unscratched. The tapwater here is moderately hard, so it has a substantial mineral content. I find that even if the water seems to have boiled in that water has been forced out of the spout and wet the inside of the microwave, it can still be superheated and will boil when a spoon is inserted, and stop when the spoon is withdrawn, and continue when the spoon is inserted again.

i'm 72. when i was a kid, i remember HOT DOGS being cooked in a weird way that smelled weird and tasted weird. the catch phrase used 'infra-red'. later, as a freshman at santa cruz, aluminum packets were routinely placed in microwave ovens. the fireworks were supposed to 'enhance' the effects of psychedelic chemicals. (they did NOT.) thanks for conjuring up those memories. BTW, there's no microwave in our house.

I have an older JC Penny's Microwave that has no turn table. I've never had a problem with it. I figured that the turn table was a cheap solution to uneven microwave distribution. My old JC Penny microwave has always heated liquids and foods very nicely. It is interesting to learn about this problem. I'm not going to worry about it though. : - )

We bought a Radar Range for Mom in 1969. I still use it today. Only repair was the light bulb. We had to license it with the FCC as a transmitter of some type.

So you think microwave ovens were expensive back in the day? My dad, if still alive, would say "you have no idea". In the early 80's my mom had been resistant to adding a microwave to the kitchen, saying there wasn't enough room for it; us kids, however, wanted one in the house and so we chipped in and bought her one as a Xmas present (Dad matched the money that we came up with). My mom's reaction was to insist on having the entire kitchen gutted and rebuilt, with the microwave built into a cabinet! This cost my Dad way more than the microwave did.....

It's more about the standing wave hotspots. Superheated water can happen with the tray, too, but less often. The container needs to be very smooth, water very pure, etc.

It is there for the wheels. Those wheels will rub the coating off from the bottom and will rust in a circle. So you have to buy a new microwave.

I don’t agree with your conclusion. Turntables were put in to replace spinning wave guides. It was the cheaper microwaves that got turntables first. Eventually most microwaves got turntables as a cost-cutting measure. Very expensive commercial microwaves have no turntable even now.

My rich neighbors had a Radar Range in the early '60s. It broke, and they didn't have anyone on the west coast to repair it. They would have had to pay for someone to fly out to fix it, or ship it back. My dad was a physicist, and I remember him and one of his colleagues taking it apart and fixing it. I bought a Litton microwave in 1978 for $649. I remember because I was making $3.50 per hour at the time. It had a waveguide over the top and stirring fans on each side. It cooked very evenly.

There are several hot springs in Yellowstone are a bit hotter than the boiling temperature at that altitude (199 F). But these springs tend to be very deep so the water farther down can get much hotter, then because the water is so clean it doesn't flash to steam and erupt like a geyser. These springs are obvious as the foam violently around the edges.

Superheating is also a problem with tank-type water heaters. The relief valve on top of every tank water heater is pressure and temperature sensitive, and without it, a tank water heater can become a quite powerful bomb. The boiling point of pressurized water is higher, and even the aqueduct pressure is enough to raise the boiling point a little bit. Now assume a tank water heater without relief valve, with a defective thermostat that allows the water inside the tank to get above the boiling point... Everything is fine until someone use hot water... The pressure inside the tank suddenly drops, therefore all the water in the tank instantly turn to steam.

Our original microwave from 1986 has a turntable, and noticed that the direction of rotation was always random. You never knew which way until it starts.

it happened to me 40 yrs ago, the stream hit me in the face...

My parents had that Amana Radarange Fran shows the manual for. Worked great for decades. I once in my current modern microwave oven that has a carousel heated up a cup of water for some tea. I heated it for 5 minutes not realizing 2 to 3 minutes would have been enough. I opened the door and the water was not boiling. I dropped the teabag in before taking the cup out. Good thing I did the teabag first because as soon as the teabag hit the water the water boiled like crazy and half the water boiled over instantly. No explosion just an instant raging boiling. I can only imagine what would have happened had I microwaved for 10 minutes.

My family's first microwave in the mid to late 80s had no turntable and it did superheat water a time or two. My mom got burned. But you can still get microwaves like that now. At work in the break rooms and cafeteria they have "industrial" microwaves that have no turntables, and it's not like they're 30 years old. A month or so back I saw a skid with several boxes of those same microwaves, brand new.

Stale donuts can be softened by a short time in a microwave, but that is a common cause of burns when doing that with jellied center donuts - the central jelly, insulated by the donut cake, gets much hotter than the exterior of the donut.

Back in the 80s we had a Nordic Ware Micro Go Round in our microwave. It helped even out the heating.

Interesting stuff ~ radar range, super heated water, microwaves, rotation and surface tension…it has it all! I like your videos very much, I always learn something. 👍

I grew up with one of these Amana RadarRange's. My parents taught me to heat it slowly, & periodically move it around & check the temperature.

Thank you Fran!

Growing up we had a RadarRange! We got it in around 1977 or so... I had a Pyrex measuring cup of water in it once and the water didn't look like it was hot at all. As soon as I grabbed the handle of the cup, the water exploded upwards all over - thankfully I was very young and I managed to pull my hand away with only minor burns. It was scary, and I had no idea what happened and was afraid to use the RadarRange for a long time after that. The other odd thing that happened was I put cut carrot pieces in it, and as soon as I turned it on the entire kitchen lit up with this bright light from inside the RadarRange, and it made a crackling and buzzing sound - there was a white fire-looking thing that came from the carrot pieces, where the carrots were touching.... I found out it was plasma!

Back in the 70's, Heathkit made a microwave oven kit. I vaguely remember it being included in a Consumer Reports' review of microwave ovens, where it got a rather mediocre rating.

Yeah, dunno. I actually deliberately superheated water in my microwave, and it has a turntable. I had a very clean mug and very hard water, I suspect that the hardness tended to fill in any minor scratches. It wasn't ridiculously superheated, maybe 105C or a bit more but the geyser when I dropped salt in with a LONG spoon, while wearing rubber gloves was extremely impressive/scary.

Hey Fran, we recently installed an under-the-counter microwave that opens like a drawer and you load the food from the top. No tray, doesn't turn the food at all. I've thought about the added danger with the drawer-type microwave. When the drawer opens you are looking directly down into the chamber.

In the 80s it was a sales point that the tray did not rotate. They rotated the part that emits the waves. That was apparently something new. Later they apparently found that the rotating tray still was better so they went back.

I love all of your videos ! Perhaps one day you could explain why microwaves have a metal rack in them. Mine has one that's above the carousel. I always thought you couldn't put metal in the microwave.

Now, I really hope that Ratheon didn't figure out Microwaves can cook as the result of unfortunate radar experiments (cough, accidents)

I agree with Gersberms; The rotation is mainly to prevent hot and cold spots in food due to standing waves inside the oven. Also prevents super-heating as you explained and the legal liability it creates.

I remember my mom talking about this phenomenon! Once when I was a kid, I don't remember what brought it up but she described superheating to me (without actually calling it that), and I remember wondering how one would actually achieve that particular set of circumstances. On a possibly related note, this was around the time my folks finally replaced their old flat-bottom microwave for one with a rotisserie in it...

I've seen gravy on a microwaved meal explode, after it's surface was pierced with a fork.

The original microwave oven was the size of a refrigerator and used 6,000 watts. It would over cook a hot dog in less than 15 seconds. It sat in the kitchen of one of the executives for decades and was still working. Finally after his passing the wife wanted to remodel and tried to get the company to come and get it.

I remember buying a plastic wind up rotating table and used it for the life of the oven. I get a kick out of some of the newer ovens that seem light in weight due to using a switcher for the power supply instead of 10 lbs of old school transformer.

High surface tension of water is what also causes painful belly flops.

The number one effect of the turntable in a microwave I noticed was far more even heating of food.

My grandma had an original Amana Radar Range in mid 60’s.

I recall my parents buying their first microwave in the late 1970's and part of the sales price was a night class cooking lesson to learn how to actually use it!

Early microwaves had a mechanical shutter reflector system in the waveguide to spread the waves evenly over the food. More expensive to get right than just rotating the food. Also shifting the waves means more usable space in the rectangle shaped oven.

I used to use a half pint glass mug to heat water for instant coffee and this would happen regularly. The water wouldn't boil until you added the coffee granules, then it would foam up and pour over the table, but no violent explosion. This is in a modern microwave with a turntable. I was using the same time setting that I used with ceramic half pint mugs which didn't do this.

I had one set up on top of my mini fridge. Bottom was at head height. Was feeling really dizzy in the mornings..cheap microwave, the bottom had rusted through under the platter quite badly but it was clean and working great to my eyes which were perfectly aligned with the tray. Making my morning coffee ..straight through the bottom and bouncy bouncy across the top of the mini fridge right where my head was👌 gj me.

We had a Sharp Carousel in the early 80’s. It lasted 20 years. New ones, 3-5 years.

Hot water can be bad, but steam, even at the same temperature, is spectacularly worse. I suspect many of you already know why, but it has to do with "heat of fusion" and "heat of vaporization" at the points where something changes state. In this case, water and usually at some nominal atmospheric pressure. For water, it is 80 calories per gram to convert ice to water and 540 calories per gram to convert water to steam. In the case of ice, ice cubes work so well because they absorb those 88 calories just converting from ice to water and after that the cold water absorbs only 1 calorie per degree C per gram as it warms above freezing. But steam has that massive 540 calories per gram. So, if you get steam on your skin, it releases all that heat just turning back into water. Steam at the boiling temperature is therefore vastly worse than water at the boiling temperature. These points are different at different atmospheric pressures (and for different substances). A common physics class experiment is to pull a partial vacuum and demonstrate water existing liquid, solid, and gas (boiling) at the same temperature in a partial vacuum. This is called the "triple point" where all three states are in equilibrium.

My first microwave oven was a Philips in the late 1980's and none of them had any rotating bottoms, still heated very evenly. Manufactured in Sweden at the time (Norrköping). I bought a new microwave 2 years ago, no rotating platter, just a smooth glass bottom, still also heats very evenly. Before that I had a Panasonic with rotated and that was a great oven, but not any better than the one I have today. As I understand it all these models (even the first Philips ones), have hidden rotating deflectors which spreads the microwaves evenly inside the oven. Some models even have two, at the top and the bottom for even better results. The thing that all such ovens have turntables to avoid superheating must be an American phenomenon (people suing companies frequently?) because where I live we always had both types up until this very day.

I'm not convinced that a rotating tray completely eliminates the possibility of superheating. And it's not like that that every new microwave today has a rotating tray. There still are models without one.

I knew someone who’s son was injured in such an accident involving a microwave and super heated water in a Pyrex measuring cup

People don't believe me when I tell them my aunt had a '53 Tappan microwave. When you turned it on you first had to let the tubes warm up. I had superheating happen once with my mid '70s microwave, I opened the door and wondered why the water hadn't boiled. I stuck a spoon into the mug. POW! I was incredibly lucky not to be injured.

I still use a carousel free microwave from 1990 and I am never getting rid of it. They are way more trouble than they are worth.

My microwave is really old. I think possibly from the late 60s. Still works great.

The Amana "Radar Range" was the first one I remember back in the 60s

Over in the UK once I heated 2 cups of water in a Pyrex measuring cup in my microwave. It beeped, I opened the door, and there were no bubbles. As soon as I touched the handle the water erupted. Scared the h*ll out of me!

No microwave in our kitchen ;-)

I was making turkey gravy in a saucepan one Thanksgiving, and being lazy just drained all the juice into the pan, figuring I'd separate the fat layer later. About the time it was showing signs of beginning to 'boil', it erupted violently, covering the stove, hood, floor with nearly all the contents. Best I could surmise was the layer of fat on top somehow setup conditions for a superheating event, and those first few bubbles piercing it triggered the release. I won't do THAT again! lol [edit] A theory / explanation from any of you fellow Eggheads of how this happened would be greatly appreciated!

I actually had this happen to me. I reached in and just touched the measuring cup of water I had heated and it exploded. I had 2nd degree burns on my hand and arm that were very painful. But we didn't sue anyone over it. Ever since if I'm boiling water in the microwave I make sure it is bubbling before I take it out. If I'm just heating water I tap the mug with a long fork or something. But I've never seen the water explode again and it's been over 35 years since I was burned. The explosion didn't break the measuring cup because all the energy went up, but the water and steam hit the roof of the microwave and rained back down on my hand and arm.

Heating water in a microwave seems a very American thing to do.

Wow, that explained what happened to my brothers several years ago. We were doing breakfast and he put a water container in the microwave (...and I think now, that for any reason the rotation was disabled). As exaggerated as he was usually, I though he set the oven power at maximum power, and I can't say for how long. I was on the other part of the table, and I remember that the oven rang, he opened the door, and I can't tell exactly what he did, but I remember a sound like a shaken gassed coke that is suddenly opened with gas explosion, and I big water splash coming from inside the oven and my brother immediately screaming for the hot water contact. Fortunately he was partially covered by the oven door, but he got some serious burn at one hand. Nobody was able to explain what hell was happened and why... until now.🙄

I'm not sure I buy this theory! You can still superheat water in a microwave with turn table, and the uneven heating resulting from not rotating is pretty marked! People don't want spots in their food still frozen. And I'm not sure I buy that it's that expensive to feed rotation through the shell!

No microwave oven in my house. Nope.