Correct me if I got anything wrong, TA!
this post was submitted on 24 Oct 2023
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It's not dangerous at all, superheating is rarely a thing and you can avoid it in a multitude of ways including slapping a spoon in your cup
If you're talking about the microwave somehow doing something to the water to make it irradiated or something (which I've also seen claimed): no
No I'm talking about superheating - OP is putting water in a smooth glass vessel with no points for bubbles to form. IT REALLY is worth mentioning to the casual viewer.
There's enough nucleation points, even in a pyrex measuring cup, to avoid superheating, as long as you're just bringing it to a rolling boil at maximum (so like 3 minutes, tops), and then using it.
The real problem comes when you microwave the water for three minutes, forget about it, then microwave it again. The nucleation points you had the first time around are now too few. Now when you pour the water into another vessel - or even just jog the water in the existing vessel - it can suddenly and explosively boil over.
If you look videos up, people have been able to many times over reliably produce superheating phenomina and "bump" (the term for the explosion) boiled water in a glass cup. Just look it up, it's actually a pretty common science experiment people have shown.
Mythbusters literally did an episode on it.
Not by heating 2 cups of water, once, for three minutes they haven't.
You can literally go look it up. It's widely avaliable info. Stop spreading dangerous disinformation.
Again - the issue is all about nucleation sites. These are "points where phase transition is favored." Nucleation sites are necessary for the heated water to change from liquid to gas.
As you heat water, it will phase shift from liquid to gas beneath the surface at these nucleation sites. That's where the bubbles and the rolling boil comes from in boiling water. So long as there are sufficient nucleation sites within the water holding on to tiny bits of air - whether those are tiny variations in the surface of the container, or particulate matter - there is no danger. If the water in the container is bubbling or rolling, there is no danger of "superheating."
The danger comes when all the little air bubbles held by those nucleation sites have already been freed and left the liquid. The water is extremely hot, but it is unable to phase shift beneath its surface. Now there is danger, because there aren't any nucleation sites left. Introducing new nucleation sites (making contact with previously uncontacted upper parts of the container, adding something like instant coffee, or pouring into another container) causes the phase shift from liquid to gas to happen again, and if the added number of nucleation sites is high enough, the whole container will try to phase shift at the same time. Because the water is in a container, with an open top, the only place for it all to go is out that top, explosively, like a bullet exiting a gun.
None of the previous paragraph will happen with potable water in a household container microwaved for three minutes.
https://mythbusters.fandom.com/wiki/Microwave_Madness
From the comment you're replying to:
It's not worrying at all unless youve never used a microwave for this purpose. I've microwaved a shit ton of water in those exact Pyrex measuring cups and never had an issue with superheating. Nobody in my family ever has going all the way back to the 60s.
That's called selection bias btw.
No one in my family has died in a car crash going back to their invention. Doesn't mean anything.
The variables involved in driving are not reliable. Even if you're the safest driver you can still be involved in an accident. The same cannot be said about repeatedly boiling water in the same vessel for years, like the person you are responding to. They are not lucky in the same way drivers are to avoid accidents.
No, it's called experience with the device and situation at hand
I'm not claiming superheating doesn't exist, I'm pointing out that the top level claim of "this is super dangerous" is fucking bunk
The people who've been burnt by super heated water also have experience with the device and situation at hand.
They'd not experience this situation as, like another commenter stated, even a pyrex glass has nucleation sites for boiling
If they've double-microwaved the water then they have a chance at superheating, but that is not the same situation as just microwaving water in a pyrex cup, the thing that was being called extremely dangerous
But sure, well just keep being scared of doing it at all because some people can't remember that they already heated something
Ah, so I should just put my metal teaspoon in my cup and I'll be fine?
(Don't put metal in the microwave.)
Yeah
Unless you mean repeatedly stopping the microwave to stir the water and starting again...
At which point I have gotta ask: why not just use a kettle?
Ah, so I should just put my metal teaspoon in my cup and I'll be fine?
(Don't put metal in the microwave.)
Fun fact: you can put a metal spoon in the microwave and be perfectly fine
As someone who has first hand witnessed a fair share of microwaves getting wrecked by people microwaving metal in them accidently, that answer is bullshit.
If the metal object gets near the (typically right) side of the microwave, it 100% will arc and at best short out the microwave, but at worst I have first hand seen it cause a fire.
The metal object effectively becomes quite a fair bit charged with electrons from the surrounding air from the microwaves running along its surface. This in turn slowly builds up a negative charge difference between the metal object and the surrounding walls.
At enough of a differential plasma will form and an arc of electricity will go from the metal object to anything it can get close to.
And if that "thing close to it" is the wall of the microwave that houses the actual unit in it, it can short out the electronics sitting in there.
Also, it can seriously harm someone if the microwave isn't grounded properly (and boy is that unfortunately more common than you may think), and they are touching the frame of the microwave, as now they are the ground.
LOOK AT ME! LOOK AT ME!
I AM THE GROUND NOW!