SAFETY - boiling water in a microwave

[Michael 345]

Microwaving Water!

A 26-year old man decided to have a cup of coffee. He took a cup of water and put it in the microwave to heat it up (something that he had done numerous times before).

I am not sure how long he set the timer for, but he wanted to bring the water to a boil. When the timer shut the oven off, he removed the cup from the oven. As he looked into the cup, he noted that the water was not boiling, but suddenly the water in the cup 'blew up' into his face.

The cup remained intact until he threw it out of his hand, but all the water had flown out into his face due to the build-up of energy . His whole face is blistered and he has 1st and 2nd degree burns to his face which may leave scarring

He also may have lost partial sight in his left eye. While at the hospital, the doctor who was attending to him stated that this is a fairly common occurrence and water (alone) should never be heated in a microwave oven.

If water is heated in this manner, something should be placed in the cup to diffuse the energy such as a wooden stir stick, tea bag, etc, (nothing metal).

General Electric's Response:

Thanks for contacting us; I will be happy to assist you. The e-mail that you received is correct. Microwaved water and other liquids do not always bubble when they reach boiling point. They can actually get superheated and not bubble at all. The superheated liquid will bubble up out of the cup when it is moved or when something like a spoon or tea bag is put into it.

To prevent this from happening and causing injury,do not heatany liquid for more thantwo minutes per cup. After heating, let the cup stand in the microwave forthirty secondsbefore moving it or adding anything into it.

Here is what a local high school science teacher had to say on the matter:

'Thanks for the microwave warning. I have seen this happen before. It is caused by a phenomenon known as super heating.

It can occur any time water is heated andwill particularly occurif the vessel that the water is heated in is new, or when heating a small amount of water(less than half a cup).

What happens is that the water heats faster than the vapor bubbles can form. If the cup is very new, then it is unlikely to have small surface scratches inside it that provide a place for the bubbles to form.

As the bubbles cannot form and release some of the heat that has built up, the liquid does not boil, and the liquid continues to heat up well past its boiling point.

What then usually happens is that the liquid is bumped or jarred, which is just enough of a shock to cause the bubbles to rapidly form and expel the hot liquid. The rapid formation of bubbles is also why a carbonated beverage spews when opened after having been shaken.

 

[James R]

Is there a question?

 

[Michael 345]

Is there a question?

Microwaving Water!

A 26-year old man decided to have a cup of coffee. He took a cup of water and put it in the microwave to heat it up (something that he had done numerous times before).

I am not sure how long he set the timer for, but he wanted to bring the water to a boil. When the timer shut the oven off, he removed the cup from the oven. As he looked into the cup, he noted that the water was not boiling, but suddenly the water in the cup 'blew up' into his face.

The cup remained intact until he threw it out of his hand, but all the water had flown out into his face due to the build-up of energy . His whole face is blistered and he has 1st and 2nd degree burns to his face which may leave scarring

He also may have lost partial sight in his left eye. While at the hospital, the doctor who was attending to him stated that this is a fairly common occurrence and water (alone) should never be heated in a microwave oven.

If water is heated in this manner, something should be placed in the cup to diffuse the energy such as a wooden stir stick, tea bag, etc, (nothing metal).

General Electric's Response:

Thanks for contacting us; I will be happy to assist you. The e-mail that you received is correct. Microwaved water and other liquids do not always bubble when they reach boiling point. They can actually get superheated and not bubble at all. The superheated liquid will bubble up out of the cup when it is moved or when something like a spoon or tea bag is put into it.

To prevent this from happening and causing injury,do not heatany liquid for more thantwo minutes per cup. After heating, let the cup stand in the microwave forthirty secondsbefore moving it or adding anything into it.

Here is what a local high school science teacher had to say on the matter:

'Thanks for the microwave warning. I have seen this happen before. It is caused by a phenomenon known as super heating.

It can occur any time water is heated andwill particularly occurif the vessel that the water is heated in is new, or when heating a small amount of water(less than half a cup).

What happens is that the water heats faster than the vapor bubbles can form. If the cup is very new, then it is unlikely to have small surface scratches inside it that provide a place for the bubbles to form.

As the bubbles cannot form and release some of the heat that has built up, the liquid does not boil, and the liquid continues to heat up well past its boiling point.

What then usually happens is that the liquid is bumped or jarred, which is just enough of a shock to cause the bubbles to rapidly form and expel the hot liquid. The rapid formation of bubbles is also why a carbonated beverage spews when opened after having been shaken.

When I first started using microwave for cups of coffee I would boil up a cupful of plain water. First never injuries. Few messes

They happened when I put the spoon of coffee in the hot water causing it to bubble up over the top of cup

Anyone done the same sort of thing?

Any other tips about operating microwave?

 

[RainbowSingularity]

Any other tips about operating microwave?

don't use cracked plates cups or bowls or glasses or mugs
they can explode from thermal warping when you open the door and take them out
or sometimes when inside heating

cracked or chipped, don't use it in the microwave
dropped and it might be cracked
don't use it

anything that is sealed creating its own air bubble should not be microwaved because it will explode .

don't put any metal in the microwave

common issue
thick soups and thick liquids

heated too quickly & not stirred, they create heat pockets which then boil & bubble up
they burn the edges and don't heat right through while creating a boiling liquid explosion risk to children\happens quite a lot to 1st time microwave users heating soups

 

[foghorn]

This may be obvious to some.
I was visiting my mother when the microwave starting ''zapping'', it was the ''gold gilt'' pattern on the plate she had placed the mince pies on to warm up.
But, she did know to remove the foil case from each pie before placing them in the microwave.

 

[DaveC426913]

This may be obvious to some.
I was visiting my mother when the microwave starting ''zapping'', it was the ''gold gilt'' pattern on the plate she had placed the mince pies on to warm up.
But, she did know to remove the foil case from each pie before placing them in the microwave.

Happened to me just a few weeks ago, with a deli sandwich wrapped in (foil-lined) paper.

I was facing away from the microwave, but the kitchen lit up like lightning. OMG, can foil-lined paper ever burn!

 

[exchemist]

View attachment 4032

Microwaving Water!

A 26-year old man decided to have a cup of coffee. He took a cup of water and put it in the microwave to heat it up (something that he had done numerous times before).

I am not sure how long he set the timer for, but he wanted to bring the water to a boil. When the timer shut the oven off, he removed the cup from the oven. As he looked into the cup, he noted that the water was not boiling, but suddenly the water in the cup 'blew up' into his face.

The cup remained intact until he threw it out of his hand, but all the water had flown out into his face due to the build-up of energy . His whole face is blistered and he has 1st and 2nd degree burns to his face which may leave scarring

He also may have lost partial sight in his left eye. While at the hospital, the doctor who was attending to him stated that this is a fairly common occurrence and water (alone) should never be heated in a microwave oven.

If water is heated in this manner, something should be placed in the cup to diffuse the energy such as a wooden stir stick, tea bag, etc, (nothing metal).

General Electric's Response:

Thanks for contacting us; I will be happy to assist you. The e-mail that you received is correct. Microwaved water and other liquids do not always bubble when they reach boiling point. They can actually get superheated and not bubble at all. The superheated liquid will bubble up out of the cup when it is moved or when something like a spoon or tea bag is put into it.

To prevent this from happening and causing injury,do not heatany liquid for more thantwo minutes per cup. After heating, let the cup stand in the microwave forthirty secondsbefore moving it or adding anything into it.

Here is what a local high school science teacher had to say on the matter:

'Thanks for the microwave warning. I have seen this happen before. It is caused by a phenomenon known as super heating.

It can occur any time water is heated andwill particularly occurif the vessel that the water is heated in is new, or when heating a small amount of water(less than half a cup).

What happens is that the water heats faster than the vapor bubbles can form. If the cup is very new, then it is unlikely to have small surface scratches inside it that provide a place for the bubbles to form.

As the bubbles cannot form and release some of the heat that has built up, the liquid does not boil, and the liquid continues to heat up well past its boiling point.

What then usually happens is that the liquid is bumped or jarred, which is just enough of a shock to cause the bubbles to rapidly form and expel the hot liquid. The rapid formation of bubbles is also why a carbonated beverage spews when opened after having been shaken.

View attachment 4032

This is about superheating of a liquid, when there are no nuclei to trigger the formation of bubbles which allow it to boil.

We used to add "anti-bumping" granules to liquids that we were distilling or evaporating in chemistry, to prevent superheating and then sudden, violent boiling - "bumping" - which could overflow the vessel or break apart the fittings. Some readers may also remember this from their school days. (In the 6th form I once caused a fire on the lab bench, as a result of failing to include anti-bumping granules)

Now for the physics, or at least my understanding of it:-

The excess pressure inside a spherical bubble, due to the surface tension of the inside surface is 2T/r (r being the radius of the bubble and T the surface tension of the liquid). So the smaller the bubble, the greater the pressure needed to inflate it. While this is a macroscopic scale formula, that won't strictly apply down to the scale of individual molecules, the picture it gives that a huge excess pressure is need to blow up a bubble from zero, is directionally correct.

Nuclei of some sort, such as a porous surface with minute air pockets or sharp edges, or a mechanical disturbance, such as moving the vessel containing the liquid, are needed to break a few molecules apart within the liquid to start the formation of the bubble. Once a bubble forms, it grows exponentially, since the excess pressure required to sustain it falls as the bubble expands.

So basically you have an unstable situation, if there are no nuclei to "seed" bubble formation. This can be pseudo-explosive, so potentially nasty.

The solution is to use a slight "dirty" container, e.g one with traces of scale from previous boiling.

 

[Michael 345]

boiling

Have a new way make coffee now
No need to boil a jug full (3 or 4 hundred ml for a 100ml coffee)
That was the reason to use microwave (only heat the 100 needed)

New way also safer than jug and microwave

One of those capsule machines - without the capsule

Put coffee in cup, place under spout, 50 ml hot water per press

3 presses and a allowance for 50 ml of milk fills my cup, $2 Kmart

 

[RainbowSingularity]

note, it may be quicker but it may use more electricity to keep the heater on
efficiency of a new kettle may be less electricity for a single boil

 

[Michael 345]

note, it may be quicker but it may use more electricity to keep the heater on
efficiency of a new kettle may be less electricity for a single boil

Nope

Switched off between cups

Even if left on it automatically goes into low power mode

Takes about a minute to warm up and pumps out hot 50ml about 20secs

 

[RainbowSingularity]

Takes about a minute to warm up and pumps out hot 50ml about 20secs

thats impressive

i wonder if a gas fired instant water heater can do the same while using natural gas
in countrys like india china & usa where they use coal fired electricity & heating it may be significantly less pollution and less CO2
making cheap ones wont pass grade in usa
but may be the only model that can make money in china & india

being able to provide a few million to build the high tech factory would be expensive and you would need some regulators on the quiet in your pocket to prevent the idea from being stolen

biggest markets india & china for tea drinking
its a MASSIVE expense to income level
when they are going to use the gas burner or coal fire or wood fire and keep that going.
it would be a very expensive luxury item for them

most investors want massive returns in exchange for betting millions on a new factory build

being able to build in a country with no regulations on product standards would be needed but that would make sales to 1st countrys almost impossible
and its 1st world investors who probably already own coffee machine tech and would spend millions fighting the idea in any way they could
dirty tricks would be 24/7

 

[Michael 345]

i wonder if a gas fired instant water heater can do the same while using natural gas

Didn't instant gas Hot Water Shower units have a pilot light?

Turn on the water, water pressure drops, gass turns on, almost instant hot shower water

Pretty dangerous and haven't seen those in years

 

[RainbowSingularity]

Didn't instant gas Hot Water Shower units have a pilot light?

Turn on the water, water pressure drops, gass turns on, almost instant hot shower water

Pretty dangerous and haven't seen those in years

spark ignition battery or non battery
you can have manual non electrical click spark

mostly having 2 different controls is completely outside usa consumers ability to think clearly
so it would not pass certification
existing accidents with gas heaters would be used to attack the market to protect existing coffee machine makers and electric jug makers whom are large companys
dirty tricks 24/7

if you built the factory in India or china you might manage it
but that takes lots of money and good connections

probably around 3 million lump sum with 6 month lease and govt jobs system
you might end up with a small scale high production for close to 8 million on a cheap factory build

8 million is a lot to speculate on assuming you can grease the right official requirements for approval and land lease and labor law requirements
etc etc
customers would be almost exclusively Indian and Chinese
and probably cater to lower income household birthday and Christmas presents as luxury items
probably make some sales to new job start young adults also
assuming they dont have a coffee machine
they may want a tea machine
local jug manufacturers would be against it.
so locating and accessing the technology for the igniter and the bottle of gas and piping might face more 24/7 dirty tricks

if you dont have the money and connections to combat the 24/7 dirty tricks you would lose your money
additionally those who advertise to accept and partner with inventors steal their ideas and then make them, themselves
THOSE type of people run the show mostly
no morals no honor, those who do have honor and morals wont be interested in the risks ad smaller potential profit margin or the political wrangling required when they already have safe bets running ok
thats the real world
i have no shortage of creative new ideas
just no honest honorable moral people to partner with

 

[Beer w/Straw]

uh...

 

[exchemist]

uh...

Nice demo.

 

[Michael 345]

uh...

Thank you

 

[exchemist]

uh...

In fact, thinking about this further, there may be another contributory factor. Conventional boiling of water involves transferring heat from a very hot surface (base of pan, electric heating element) into the cooler bulk of the liquid. So as boiling point is approached, a layer of water next to the hot surface may become superheated. But the moment this superheated layer finally boils, it is safely "quenched" by the bulk liquid, which is not yet at boiling point. So there is not much danger of the bulk liquid becoming superheated. Whereas a microwave oven heats the water evenly throughout - or nearly so - with no part liable to form bubbles first and thereby "defuse" the potential for superheating of the rest.

So it all reaches boiling point at once and so, if it superheats, it ALL superheats!

 

[Michael 345]

Can any mod please rename this thread SAFETY IN GENERAL
Thank you

This short video is about the importance of wearing Safety Vest

 

[wegs]

I like watching water boil on the stove lol Not sure if I’ve ever heated anything in the microwave, to the point of boiling/scorching/burning. Hmm.

 

[Seattle]

I like watching water boil on the stove lol Not sure if I’ve ever heated anything in the microwave, to the point of boiling/scorching/burning. Hmm.

https://thumbs.gfycat.com/HeftyLeanIsabellinewheatear-mobile.mp4